How do I read / convert an InputStream into a String in Java?
如果您有一个
假设我有一个包含文本数据的
把
1 2 3 |
一个很好的方法是使用ApacheCommons
1 2 3 | StringWriter writer = new StringWriter(); IOUtils.copy(inputStream, writer, encoding); String theString = writer.toString(); |
甚至
1 2 | // NB: does not close inputStream, you'll have to use try-with-resources for that String theString = IOUtils.toString(inputStream, encoding); |
或者,如果不想混合流和作者,可以使用
这是一种只使用标准Java库的方法(注意,流没有关闭,您的里程可能会有所不同)。
1 2 3 4 | static String convertStreamToString(java.io.InputStream is) { java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A"); return s.hasNext() ? s.next() :""; } |
我从"愚蠢的扫描器技巧"一文中学到了这个技巧。它工作的原因是因为scanner迭代流中的令牌,在这种情况下,我们使用"输入边界的开始"(a)分离令牌,从而只为流的整个内容提供一个令牌。
注意,如果需要具体说明输入流的编码,可以向
帽子的尖端也属于雅各布,他曾经指给我看那篇文章。
Summarize other answers I found 11 main ways to do this(see below).我写了一些表演测试(见下面的结果):
Ways to convert an inputstream to a string:
使用
1 |
使用EDOCX1&6
1 2 |
使用
1 2 | Scanner s = new Scanner(inputStream).useDelimiter("\\A"); String result = s.hasNext() ? s.next() :""; |
Using Stream API(Java 8).警告:这个解决方案将不同的线路断裂(如
)转化为
1 2 3 | String result = new BufferedReader(new InputStreamReader(inputStream)) .lines().collect(Collectors.joining(" ")); |
使用平行流API(Java 8).警告:这个解决方案将不同的线路断裂(如
)转化为
1 2 3 | String result = new BufferedReader(new InputStreamReader(inputStream)).lines() .parallel().collect(Collectors.joining(" ")); |
使用
1 2 3 4 5 6 7 8 9 10 11 | final int bufferSize = 1024; final char[] buffer = new char[bufferSize]; final StringBuilder out = new StringBuilder(); Reader in = new InputStreamReader(inputStream,"UTF-8"); for (; ; ) { int rsz = in.read(buffer, 0, buffer.length); if (rsz < 0) break; out.append(buffer, 0, rsz); } return out.toString(); |
使用
1 2 3 | StringWriter writer = new StringWriter(); IOUtils.copy(inputStream, writer,"UTF-8"); return writer.toString(); |
使用
1 2 3 4 5 6 7 8 | ByteArrayOutputStream result = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int length; while ((length = inputStream.read(buffer)) != -1) { result.write(buffer, 0, length); } // StandardCharsets.UTF_8.name() > JDK 7 return result.toString("UTF-8"); |
使用
1 2 3 4 5 6 7 8 9 | String newLine = System.getProperty("line.separator"); BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream)); StringBuilder result = new StringBuilder(); boolean flag = false; for (String line; (line = reader.readLine()) != null; ) { result.append(flag? newLine:"").append(line); flag = true; } return result.toString(); |
使用
1 2 3 4 5 6 7 8 9 | BufferedInputStream bis = new BufferedInputStream(inputStream); ByteArrayOutputStream buf = new ByteArrayOutputStream(); int result = bis.read(); while(result != -1) { buf.write((byte) result); result = bis.read(); } // StandardCharsets.UTF_8.name() > JDK 7 return buf.toString("UTF-8"); |
使用
1 2 3 4 5 6 | int ch; StringBuilder sb = new StringBuilder(); while((ch = inputStream.read()) != -1) sb.append((char)ch); reset(); return sb.toString(); |
警告:
解决方案4、5和9将不同的线路切断为一条。
解决方案11无法用统一文本正确地工作
性能测试
小
1 2 3 4 5 6 7 8 9 10 11 12 | Benchmark Mode Cnt Score Error Units 8. ByteArrayOutputStream and read (JDK) avgt 10 1,343 ± 0,028 us/op 6. InputStreamReader and StringBuilder (JDK) avgt 10 6,980 ± 0,404 us/op 10. BufferedInputStream, ByteArrayOutputStream avgt 10 7,437 ± 0,735 us/op 11. InputStream.read() and StringBuilder (JDK) avgt 10 8,977 ± 0,328 us/op 7. StringWriter and IOUtils.copy (Apache) avgt 10 10,613 ± 0,599 us/op 1. IOUtils.toString (Apache Utils) avgt 10 10,605 ± 0,527 us/op 3. Scanner (JDK) avgt 10 12,083 ± 0,293 us/op 2. CharStreams (guava) avgt 10 12,999 ± 0,514 us/op 4. Stream Api (Java 8) avgt 10 15,811 ± 0,605 us/op 9. BufferedReader (JDK) avgt 10 16,038 ± 0,711 us/op 5. parallel Stream Api (Java 8) avgt 10 21,544 ± 0,583 us/op |
Github(Mode=平均时间,System=Linux,score 2007 715 is the best):
1 2 3 4 5 6 7 8 9 10 11 12 | Benchmark Mode Cnt Score Error Units 8. ByteArrayOutputStream and read (JDK) avgt 10 200,715 ± 18,103 us/op 1. IOUtils.toString (Apache Utils) avgt 10 300,019 ± 8,751 us/op 6. InputStreamReader and StringBuilder (JDK) avgt 10 347,616 ± 130,348 us/op 7. StringWriter and IOUtils.copy (Apache) avgt 10 352,791 ± 105,337 us/op 2. CharStreams (guava) avgt 10 420,137 ± 59,877 us/op 9. BufferedReader (JDK) avgt 10 632,028 ± 17,002 us/op 5. parallel Stream Api (Java 8) avgt 10 662,999 ± 46,199 us/op 4. Stream Api (Java 8) avgt 10 701,269 ± 82,296 us/op 10. BufferedInputStream, ByteArrayOutputStream avgt 10 740,837 ± 5,613 us/op 3. Scanner (JDK) avgt 10 751,417 ± 62,026 us/op 11. InputStream.read() and StringBuilder (JDK) avgt 10 2919,350 ± 1101,942 us/op |
视窗7系统输入流长度的性能测试MGX1〔0〕
性能测试(平均时间)取决于窗口7系统的输入流长度:
1 2 3 4 5 6 7 8 9 10 11 12 13 | length 182 546 1092 3276 9828 29484 58968 test8 0.38 0.938 1.868 4.448 13.412 36.459 72.708 test4 2.362 3.609 5.573 12.769 40.74 81.415 159.864 test5 3.881 5.075 6.904 14.123 50.258 129.937 166.162 test9 2.237 3.493 5.422 11.977 45.98 89.336 177.39 test6 1.261 2.12 4.38 10.698 31.821 86.106 186.636 test7 1.601 2.391 3.646 8.367 38.196 110.221 211.016 test1 1.529 2.381 3.527 8.411 40.551 105.16 212.573 test3 3.035 3.934 8.606 20.858 61.571 118.744 235.428 test2 3.136 6.238 10.508 33.48 43.532 118.044 239.481 test10 1.593 4.736 7.527 20.557 59.856 162.907 323.147 test11 3.913 11.506 23.26 68.644 207.591 600.444 1211.545 |
Apache Commons允许:
1 |
当然,除了UTF-8,您还可以选择其他字符编码。
另请参见:(文档)
考虑到文件,首先应该得到一个
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | public static String slurp(final InputStream is, final int bufferSize) { final char[] buffer = new char[bufferSize]; final StringBuilder out = new StringBuilder(); try (Reader in = new InputStreamReader(is,"UTF-8")) { for (;;) { int rsz = in.read(buffer, 0, buffer.length); if (rsz < 0) break; out.append(buffer, 0, rsz); } } catch (UnsupportedEncodingException ex) { /* ... */ } catch (IOException ex) { /* ... */ } return out.toString(); } |
用途:
1 2 3 4 5 6 7 8 9 10 11 12 | InputStream in = /* Your InputStream */; StringBuilder sb = new StringBuilder(); BufferedReader br = new BufferedReader(new InputStreamReader(in)); String read; while ((read=br.readLine()) != null) { //System.out.println(read); sb.append(read); } br.close(); return sb.toString(); |
如果您使用google collections/guava,可以执行以下操作:
1 2 3 | InputStream stream = ... String content = CharStreams.toString(new InputStreamReader(stream, Charsets.UTF_8)); Closeables.closeQuietly(stream); |
注意,
这是我的纯Java和Android解决方案,它工作得很好…
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | public String readFullyAsString(InputStream inputStream, String encoding) throws IOException { return readFully(inputStream).toString(encoding); } public byte[] readFullyAsBytes(InputStream inputStream) throws IOException { return readFully(inputStream).toByteArray(); } private ByteArrayOutputStream readFully(InputStream inputStream) throws IOException { ByteArrayOutputStream baos = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int length = 0; while ((length = inputStream.read(buffer)) != -1) { baos.write(buffer, 0, length); } return baos; } |
下面是一些实验后我想出的最优雅、纯粹的Java(无库)解决方案:
1 2 3 4 5 6 7 8 9 10 11 12 | public static String fromStream(InputStream in) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader(in)); StringBuilder out = new StringBuilder(); String newLine = System.getProperty("line.separator"); String line; while ((line = reader.readLine()) != null) { out.append(line); out.append(newLine); } return out.toString(); } |
用途:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | import java.io.BufferedInputStream; import java.io.ByteArrayOutputStream; import java.io.InputStream; import java.io.IOException; public static String readInputStreamAsString(InputStream in) throws IOException { BufferedInputStream bis = new BufferedInputStream(in); ByteArrayOutputStream buf = new ByteArrayOutputStream(); int result = bis.read(); while(result != -1) { byte b = (byte)result; buf.write(b); result = bis.read(); } return buf.toString(); } |
For completeness here is Java 9 solution:
1 2 3 | public static String toString(InputStream input) throws IOException { return new String(input.readAllBytes(), StandardCharsets.UTF_8); } |
目前在JDK 9主编码中,所以在释放时会出现。你现在可以用JDK 9突击步枪大楼试试看。
我在这里做了14个不同答案的基准(抱歉没有提供学分,但有太多的重复)。
结果非常令人惊讶。结果表明,ApacheIOutils是最慢的,
因此,首先是最好的方法:
1 2 3 4 5 6 7 8 9 10 11 | public String inputStreamToString(InputStream inputStream) throws IOException { try(ByteArrayOutputStream result = new ByteArrayOutputStream()) { byte[] buffer = new byte[1024]; int length; while ((length = inputStream.read(buffer)) != -1) { result.write(buffer, 0, length); } return result.toString(UTF_8); } } |
20个周期内20 MB随机字节的基准测试结果
时间(毫秒)
- BytearrayOutputStream测试:194
- 尼罗河:198
- JAVA9ISTRANSFERTO:201号
- java9isreadallbytes:205个
- BufferedInputStreamVsBytearrayOutputStream:314
- ApacheStringWriter2:574
- 瓜瓦卡河:589
- 扫描仪读卡器非文本测试:614
- 扫描仪读卡器:633
- 阿帕切斯特林格:1544
- streamapi:错误
- ParallelStreamAPI:错误
- BufferReaderTest:错误
- InputStreamAndStringBuilder:错误
基准源代码
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 | import com.google.common.io.CharStreams; import org.apache.commons.io.IOUtils; import java.io.*; import java.nio.ByteBuffer; import java.nio.channels.Channels; import java.nio.channels.ReadableByteChannel; import java.nio.channels.WritableByteChannel; import java.util.Arrays; import java.util.List; import java.util.Random; import java.util.stream.Collectors; /** * Created by Ilya Gazman on 2/13/18. */ public class InputStreamToString { private static final String UTF_8 ="UTF-8"; public static void main(String... args) { log("App started"); byte[] bytes = new byte[1024 * 1024]; new Random().nextBytes(bytes); log("Stream is ready "); try { test(bytes); } catch (IOException e) { e.printStackTrace(); } } private static void test(byte[] bytes) throws IOException { List<Stringify> tests = Arrays.asList( new ApacheStringWriter(), new ApacheStringWriter2(), new NioStream(), new ScannerReader(), new ScannerReaderNoNextTest(), new GuavaCharStreams(), new StreamApi(), new ParallelStreamApi(), new ByteArrayOutputStreamTest(), new BufferReaderTest(), new BufferedInputStreamVsByteArrayOutputStream(), new InputStreamAndStringBuilder(), new Java9ISTransferTo(), new Java9ISReadAllBytes() ); String solution = new String(bytes,"UTF-8"); for (Stringify test : tests) { try (ByteArrayInputStream inputStream = new ByteArrayInputStream(bytes)) { String s = test.inputStreamToString(inputStream); if (!s.equals(solution)) { log(test.name() +": Error"); continue; } } long startTime = System.currentTimeMillis(); for (int i = 0; i < 20; i++) { try (ByteArrayInputStream inputStream = new ByteArrayInputStream(bytes)) { test.inputStreamToString(inputStream); } } log(test.name() +":" + (System.currentTimeMillis() - startTime)); } } private static void log(String message) { System.out.println(message); } interface Stringify { String inputStreamToString(InputStream inputStream) throws IOException; default String name() { return this.getClass().getSimpleName(); } } static class ApacheStringWriter implements Stringify { @Override public String inputStreamToString(InputStream inputStream) throws IOException { StringWriter writer = new StringWriter(); IOUtils.copy(inputStream, writer, UTF_8); return writer.toString(); } } static class ApacheStringWriter2 implements Stringify { @Override public String inputStreamToString(InputStream inputStream) throws IOException { return IOUtils.toString(inputStream, UTF_8); } } static class NioStream implements Stringify { @Override public String inputStreamToString(InputStream in) throws IOException { ReadableByteChannel channel = Channels.newChannel(in); ByteBuffer byteBuffer = ByteBuffer.allocate(1024 * 16); ByteArrayOutputStream bout = new ByteArrayOutputStream(); WritableByteChannel outChannel = Channels.newChannel(bout); while (channel.read(byteBuffer) > 0 || byteBuffer.position() > 0) { byteBuffer.flip(); //make buffer ready for write outChannel.write(byteBuffer); byteBuffer.compact(); //make buffer ready for reading } channel.close(); outChannel.close(); return bout.toString(UTF_8); } } static class ScannerReader implements Stringify { @Override public String inputStreamToString(InputStream is) throws IOException { java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A"); return s.hasNext() ? s.next() :""; } } static class ScannerReaderNoNextTest implements Stringify { @Override public String inputStreamToString(InputStream is) throws IOException { java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A"); return s.next(); } } static class GuavaCharStreams implements Stringify { @Override public String inputStreamToString(InputStream is) throws IOException { return CharStreams.toString(new InputStreamReader( is, UTF_8)); } } static class StreamApi implements Stringify { @Override public String inputStreamToString(InputStream inputStream) throws IOException { return new BufferedReader(new InputStreamReader(inputStream)) .lines().collect(Collectors.joining(" ")); } } static class ParallelStreamApi implements Stringify { @Override public String inputStreamToString(InputStream inputStream) throws IOException { return new BufferedReader(new InputStreamReader(inputStream)).lines() .parallel().collect(Collectors.joining(" ")); } } static class ByteArrayOutputStreamTest implements Stringify { @Override public String inputStreamToString(InputStream inputStream) throws IOException { try(ByteArrayOutputStream result = new ByteArrayOutputStream()) { byte[] buffer = new byte[1024]; int length; while ((length = inputStream.read(buffer)) != -1) { result.write(buffer, 0, length); } return result.toString(UTF_8); } } } static class BufferReaderTest implements Stringify { @Override public String inputStreamToString(InputStream inputStream) throws IOException { String newLine = System.getProperty("line.separator"); BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream)); StringBuilder result = new StringBuilder(UTF_8); String line; boolean flag = false; while ((line = reader.readLine()) != null) { result.append(flag ? newLine :"").append(line); flag = true; } return result.toString(); } } static class BufferedInputStreamVsByteArrayOutputStream implements Stringify { @Override public String inputStreamToString(InputStream inputStream) throws IOException { BufferedInputStream bis = new BufferedInputStream(inputStream); ByteArrayOutputStream buf = new ByteArrayOutputStream(); int result = bis.read(); while (result != -1) { buf.write((byte) result); result = bis.read(); } return buf.toString(UTF_8); } } static class InputStreamAndStringBuilder implements Stringify { @Override public String inputStreamToString(InputStream inputStream) throws IOException { int ch; StringBuilder sb = new StringBuilder(UTF_8); while ((ch = inputStream.read()) != -1) sb.append((char) ch); return sb.toString(); } } static class Java9ISTransferTo implements Stringify { @Override public String inputStreamToString(InputStream inputStream) throws IOException { ByteArrayOutputStream bos = new ByteArrayOutputStream(); inputStream.transferTo(bos); return bos.toString(UTF_8); } } static class Java9ISReadAllBytes implements Stringify { @Override public String inputStreamToString(InputStream inputStream) throws IOException { return new String(inputStream.readAllBytes(), UTF_8); } } } |
我会使用一些Java 8技巧。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | public static String streamToString(final InputStream inputStream) throws Exception { // buffering optional try ( final BufferedReader br = new BufferedReader(new InputStreamReader(inputStream)) ) { // parallel optional return br.lines().parallel().collect(Collectors.joining(" ")); } catch (final IOException e) { throw new RuntimeException(e); // whatever. } } |
基本上和其他答案一样,只是更简洁。
我做了一些计时测试,因为时间总是很重要的。
我试图以3种不同的方式将响应变成字符串。(如下所示)
为了可读性,我省略了try/catch块。
为了给出上下文,这是所有3种方法的前面代码:
1 2 3 4 |
1)
1 | response = method.getResponseBodyAsString(); |
2)
1 2 3 4 5 6 7 8 9 | InputStream resp = method.getResponseBodyAsStream(); InputStreamReader is=new InputStreamReader(resp); BufferedReader br=new BufferedReader(is); String read = null; StringBuffer sb = new StringBuffer(); while((read = br.readLine()) != null) { sb.append(read); } response = sb.toString(); |
3)
1 2 3 4 | InputStream iStream = method.getResponseBodyAsStream(); StringWriter writer = new StringWriter(); IOUtils.copy(iStream, writer,"UTF-8"); response = writer.toString(); |
因此,在对具有相同请求/响应数据的每个方法运行500个测试之后,下面是数字。再一次,这些是我的发现,你的发现可能不完全相同,但我写这篇文章是为了给其他人一些关于这些方法效率差异的指示。
排名:
进近1
接近3-2.6%慢于1
接近2-比1慢4.3%
这些方法中的任何一种都是获取响应并从中创建字符串的适当解决方案。
纯爪哇溶液使用流体,自爪哇8号以来的作品。
1 2 3 4 5 6 7 8 9 10 11 12 | import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.util.stream.Collectors; // ... public static String inputStreamToString(InputStream is) throws IOException { try (BufferedReader br = new BufferedReader(new InputStreamReader(is))) { return br.lines().collect(Collectors.joining(System.lineSeparator())); } } |
克里斯托弗·哈马斯特说谎?另一个答案是,具体地说,这辆车是安全的。I.E.The inputstreamreader constructor can be changes as follows:
1 |
这里或多或少是sampath的答案,清理了一点并表示为一个函数:
1 2 3 4 5 6 7 8 | String streamToString(InputStream in) throws IOException { StringBuilder out = new StringBuilder(); BufferedReader br = new BufferedReader(new InputStreamReader(in)); for(String line = br.readLine(); line != null; line = br.readLine()) out.append(line); br.close(); return out.toString(); } |
如果你觉得冒险,你可以混合斯卡拉和Java,并最终与此:
1 | scala.io.Source.fromInputStream(is).mkString("") |
将Java和Scala代码和库混合有好处。
请参阅此处的完整描述:将inputstream转换为scala中字符串的惯用方法
如果不能使用commons io(fileutils/ioutils/copyutils),下面是一个使用bufferedreader逐行读取文件的示例:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | public class StringFromFile { public static void main(String[] args) /*throws UnsupportedEncodingException*/ { InputStream is = StringFromFile.class.getResourceAsStream("file.txt"); BufferedReader br = new BufferedReader(new InputStreamReader(is/*,"UTF-8"*/)); final int CHARS_PER_PAGE = 5000; //counting spaces StringBuilder builder = new StringBuilder(CHARS_PER_PAGE); try { for(String line=br.readLine(); line!=null; line=br.readLine()) { builder.append(line); builder.append(' '); } } catch (IOException ignore) { } String text = builder.toString(); System.out.println(text); } } |
或者,如果您想要原始速度,我建议对paul de vrieze的建议进行更改(这样可以避免使用StringWriter(内部使用StringBuffer)):
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | public class StringFromFileFast { public static void main(String[] args) /*throws UnsupportedEncodingException*/ { InputStream is = StringFromFileFast.class.getResourceAsStream("file.txt"); InputStreamReader input = new InputStreamReader(is/*,"UTF-8"*/); final int CHARS_PER_PAGE = 5000; //counting spaces final char[] buffer = new char[CHARS_PER_PAGE]; StringBuilder output = new StringBuilder(CHARS_PER_PAGE); try { for(int read = input.read(buffer, 0, buffer.length); read != -1; read = input.read(buffer, 0, buffer.length)) { output.append(buffer, 0, read); } } catch (IOException ignore) { } String text = output.toString(); System.out.println(text); } } |
这是一个改编自
1 2 3 4 5 6 7 8 9 10 11 12 13 | private static final int BUFFER_SIZE = 4 * 1024; public static String inputStreamToString(InputStream inputStream, String charsetName) throws IOException { StringBuilder builder = new StringBuilder(); InputStreamReader reader = new InputStreamReader(inputStream, charsetName); char[] buffer = new char[BUFFER_SIZE]; int length; while ((length = reader.read(buffer)) != -1) { builder.append(buffer, 0, length); } return builder.toString(); } |
如果使用流读取器,请确保在结束时关闭流
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | private String readStream(InputStream iStream) throws IOException { //build a Stream Reader, it can read char by char InputStreamReader iStreamReader = new InputStreamReader(iStream); //build a buffered Reader, so that i can read whole line at once BufferedReader bReader = new BufferedReader(iStreamReader); String line = null; StringBuilder builder = new StringBuilder(); while((line = bReader.readLine()) != null) { //Read till end builder.append(line); builder.append(" "); // append new line to preserve lines } bReader.close(); //close all opened stuff iStreamReader.close(); //iStream.close(); //EDIT: Let the creator of the stream close it! // some readers may auto close the inner stream return builder.toString(); } |
编辑:在JDK7+上,可以使用Try with Resources构造。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | /** * Reads the stream into a string * @param iStream the input stream * @return the string read from the stream * @throws IOException when an IO error occurs */ private String readStream(InputStream iStream) throws IOException { //Buffered reader allows us to read line by line try (BufferedReader bReader = new BufferedReader(new InputStreamReader(iStream))){ StringBuilder builder = new StringBuilder(); String line; while((line = bReader.readLine()) != null) { //Read till end builder.append(line); builder.append(" "); // append new line to preserve lines } return builder.toString(); } } |
这里是在不使用任何第三方库的情况下将
1 2 3 4 5 6 7 | public static String getString( InputStream is) throws IOException { int ch; StringBuilder sb = new StringBuilder(); while((ch = is.read()) != -1) sb.append((char)ch); return sb.toString(); } |
下面介绍如何仅使用JDK使用字节数组缓冲区。这实际上就是通用IO
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | import java.io.ByteArrayOutputStream; import java.io.InputStream; ... InputStream is = .... ByteArrayOutputStream baos = new ByteArrayOutputStream(8192); byte[] buffer = new byte[8192]; int count = 0; try { while ((count = is.read(buffer)) != -1) { baos.write(buffer, 0, count); } } finally { try { is.close(); } catch (Exception ignore) { } } String charset ="UTF-8"; String inputStreamAsString = baos.toString(charset); |
Another one,for all the spring users:
1 2 3 4 5 6 | import java.nio.charset.StandardCharsets; import org.springframework.util.FileCopyUtils; public String convertStreamToString(InputStream is) throws IOException { return new String(FileCopyUtils.copyToByteArray(is), StandardCharsets.UTF_8); } |
在
Use the java.io.inputstream.transferto(outputstream)supported in Java 9 and the bytearrayoutputstream.tostring(string)which takes the charset name:
1 2 3 4 5 | public static String gobble(InputStream in, String charsetName) throws IOException { ByteArrayOutputStream bos = new ByteArrayOutputStream(); in.transferTo(bos); return bos.toString(charsetName); } |
Kotlin users simply do:
1 |
whereas
ZZU1
Is Kotlin Standard Library's Buill-in Extension Method.
这个很好,因为:
- 用手保护字符集。
- 您可以控制读取缓冲区的大小。
- 您可以设置生成器的长度,但不能精确设置。
- 没有库依赖项。
- 是Java 7或更高版本。
为了什么?
1 2 3 4 5 6 7 8 9 | public static String convertStreamToString(InputStream is) { if (is == null) return null; StringBuilder sb = new StringBuilder(2048); // Define a size if you have an idea of it. char[] read = new char[128]; // Your buffer size. try (InputStreamReader ir = new InputStreamReader(is, StandardCharsets.UTF_8)) { for (int i; -1 != (i = ir.read(read)); sb.append(read, 0, i)); } catch (Throwable t) {} return sb.toString(); } |
JDK中最简单的方法是使用以下代码截图。
1 2 3 4 | String convertToString(InputStream in){ String resource = new Scanner(in).useDelimiter("\\Z").next(); return resource; } |
这是我的Java 8号解决方案,用新的流程API收集所有线条的
1 2 3 4 5 6 | public static String toString(InputStream inputStream) { BufferedReader reader = new BufferedReader( new InputStreamReader(inputStream)); return reader.lines().collect(Collectors.joining( System.getProperty("line.separator"))); } |
In terms of EDOCX1&3,and EDOCX1&4),it can be expressed in Java 8 as:
1 2 | String fromFile = new BufferedReader(new InputStreamReader(inputStream)).lines().reduce(String::concat).get(); |
在Groovy中
1 | inputStream.getText() |
Raghu K Nair是唯一一个使用扫描仪的人。我使用的代码有点不同:
1 2 3 4 5 6 7 8 9 10 11 12 | String convertToString(InputStream in){ Scanner scanner = new Scanner(in) scanner.useDelimiter("\\A"); boolean hasInput = scanner.hasNext(); if (hasInput) { return scanner.next(); } else { return null; } } |
关于Delimiters:如何在Java扫描仪中使用定界符?
1 2 3 4 5 6 7 8 9 10 | InputStream is = Context.openFileInput(someFileName); // whatever format you have ByteArrayOutputStream bos = new ByteArrayOutputStream(); byte[] b = new byte[8192]; for (int bytesRead; (bytesRead = is.read(b)) != -1;) { bos.write(b, 0, bytesRead); } String output = bos.toString(someEncoding); |
我写了一个这样的课程,所以我想我会和大家分享。有时,您不想仅仅为了一件事就添加ApacheCommons,并且想要比不检查内容的扫描器更愚蠢的东西。
用法如下
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以下是readersink的代码:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 | import java.io.*; import java.nio.charset.Charset; /** * A simple sink class that drains a {@link Reader} to a {@link String} or * to a {@link Writer}. * * @author Ben Barkay * @version 2/20/2014 */ public class ReaderSink { /** * The default buffer size to use if no buffer size was specified. */ public static final int DEFAULT_BUFFER_SIZE = 1024; /** * The {@link Reader} that will be drained. */ private final Reader in; /** * Constructs a new {@code ReaderSink} for the specified file and charset. * @param file The file to read from. * @param charset The charset to use. * @throws FileNotFoundException If the file was not found on the filesystem. */ public ReaderSink(File file, Charset charset) throws FileNotFoundException { this(new FileInputStream(file), charset); } /** * Constructs a new {@code ReaderSink} for the specified {@link InputStream}. * @param in The {@link InputStream} to drain. * @param charset The charset to use. */ public ReaderSink(InputStream in, Charset charset) { this(new InputStreamReader(in, charset)); } /** * Constructs a new {@code ReaderSink} for the specified {@link Reader}. * @param in The reader to drain. */ public ReaderSink(Reader in) { this.in = in; } /** * Drains the data from the underlying {@link Reader}, returning a {@link String} containing * all of the read information. This method will use {@link #DEFAULT_BUFFER_SIZE} for * its buffer size. * @return A {@link String} containing all of the information that was read. */ public String drain() throws IOException { return drain(DEFAULT_BUFFER_SIZE); } /** * Drains the data from the underlying {@link Reader}, returning a {@link String} containing * all of the read information. * @param bufferSize The size of the buffer to use when reading. * @return A {@link String} containing all of the information that was read. */ public String drain(int bufferSize) throws IOException { StringWriter stringWriter = new StringWriter(); drainTo(stringWriter, bufferSize); return stringWriter.toString(); } /** * Drains the data from the underlying {@link Reader}, writing it to the * specified {@link Writer}. This method will use {@link #DEFAULT_BUFFER_SIZE} for * its buffer size. * @param out The {@link Writer} to write to. */ public void drainTo(Writer out) throws IOException { drainTo(out, DEFAULT_BUFFER_SIZE); } /** * Drains the data from the underlying {@link Reader}, writing it to the * specified {@link Writer}. * @param out The {@link Writer} to write to. * @param bufferSize The size of the buffer to use when reader. */ public void drainTo(Writer out, int bufferSize) throws IOException { char[] buffer = new char[bufferSize]; int read; while ((read = in.read(buffer)) > -1) { out.write(buffer, 0, read); } } } |
下面的代码适用于我。
1 2 3 4 5 | URL url = MyClass.class.getResource("/" + configFileName); BufferedInputStream bi = (BufferedInputStream) url.getContent(); byte[] buffer = new byte[bi.available() ]; int bytesRead = bi.read(buffer); String out = new String(buffer); |
请注意,根据Java文档,EDCOX1×0的方法可能不适用于EDCOX1 OR 1,但总是使用EDCOX1 2。如果您不想使用
1 2 3 4 5 6 | URL url = MyClass.class.getResource("/" + configFileName); BufferedInputStream bi = (BufferedInputStream) url.getContent(); File f = new File(url.getPath()); byte[] buffer = new byte[ (int) f.length()]; int bytesRead = bi.read(buffer); String out = new String(buffer); |
我不确定是否会有编码问题。如果代码有任何问题,请评论。
Guava提供了大量的短效率自动闭锁解决方案,当输入流从典型的路径资源来(这似乎是一个流行的任务):
1 | byte[] bytes = Resources.toByteArray(classLoader.getResource(path)); |
黄金
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还有一个一般的拜土思想和夏源思想,那就是人类既要开启又要关闭河流。
So,for example,instead of explicitly opening a small file to read its contents:
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或只是
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Based on the second part of the accepted Apache commons answer but with the small gap filled in for always closing the stream:
1 2 3 4 5 6 | String theString; try { theString = IOUtils.toString(inputStream, encoding); } finally { IOUtils.closeQuietly(inputStream); } |
JDK 7/8应答,关闭流并仍抛出IOException:
1 2 3 4 5 6 7 8 | StringBuilder build = new StringBuilder(); byte[] buf = new byte[1024]; int length; try (InputStream is = getInputStream()) { while ((length = is.read(buf)) != -1) { build.append(new String(buf, 0, length)); } } |
试试这4种说法。
根据Fred回忆的观点,不建议在
1 2 3 4 5 6 7 8 9 10 | public String convertStreamToString(InputStream is) { int k; StringBuffer sb=new StringBuffer(); while((k=fin.read()) != -1) { sb.append((char)k); } return sb.toString(); } |
不推荐,但这也是一种方法
1 2 3 4 5 6 7 8 9 | public String convertStreamToString(InputStream is) { int k; String st=""; while((k=is.read()) != -1) { st+=(char)k; } return st; } |
您可以使用Apache Commons。
在ioutils中,您可以找到具有三个有用实现的toString方法。
1 2 3 4 5 6 7 8 9 10 11 12 | public static String toString(InputStream input) throws IOException { return toString(input, Charset.defaultCharset()); } public static String toString(InputStream input) throws IOException { return toString(input, Charset.defaultCharset()); } public static String toString(InputStream input, String encoding) throws IOException { return toString(input, Charsets.toCharset(encoding)); } |
与Okio:
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好吧,你可以自己编程…这并不复杂…
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | String Inputstream2String (InputStream is) throws IOException { final int PKG_SIZE = 1024; byte[] data = new byte [PKG_SIZE]; StringBuilder buffer = new StringBuilder(PKG_SIZE * 10); int size; size = is.read(data, 0, data.length); while (size > 0) { String str = new String(data, 0, size); buffer.append(str); size = is.read(data, 0, data.length); } return buffer.toString(); } |
1 2 3 4 5 6 | public String read(InputStream in) throws IOException { try (BufferedReader buffer = new BufferedReader(new InputStreamReader(in))) { return buffer.lines().collect(Collectors.joining(" ")); } } |
你可以用仙人掌:
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UTF-8编码是默认编码。如果您需要另一个:
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ISO-859-1
如果您知道输入流的编码是iso-8859-1或ascii,那么下面是一种非常有效的方法。它(1)避免了
1 2 3 4 5 6 7 8 9 10 11 | public static String iso_8859_1(InputStream is) throws IOException { StringBuilder chars = new StringBuilder(Math.max(is.available(), 4096)); byte[] buffer = new byte[4096]; int n; while ((n = is.read(buffer)) != -1) { for (int i = 0; i < n; i++) { chars.append((char)(buffer[i] & 0xFF)); } } return chars.toString(); } |
UTF-8
对于使用utf-8编码的流,也可以使用相同的一般策略:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | public static String utf8(InputStream is) throws IOException { StringBuilder chars = new StringBuilder(Math.max(is.available(), 4096)); byte[] buffer = new byte[4096]; int n; int state = 0; while ((n = is.read(buffer)) != -1) { for (int i = 0; i < n; i++) { if ((state = nextStateUtf8(state, buffer[i])) >= 0) { chars.appendCodePoint(state); } else if (state == -1) { //error state = 0; chars.append('\uFFFD'); //replacement char } } } return chars.toString(); } |
其中
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 | /** * Returns the next UTF-8 state given the next byte of input and the current state. * If the input byte is the last byte in a valid UTF-8 byte sequence, * the returned state will be the corresponding unicode character (in the range of 0 through 0x10FFFF). * Otherwise, a negative integer is returned. A state of -1 is returned whenever an * invalid UTF-8 byte sequence is detected. */ static int nextStateUtf8(int currentState, byte nextByte) { switch (currentState & 0xF0000000) { case 0: if ((nextByte & 0x80) == 0) { //0 trailing bytes (ASCII) return nextByte; } else if ((nextByte & 0xE0) == 0xC0) { //1 trailing byte if (nextByte == (byte) 0xC0 || nextByte == (byte) 0xC1) { //0xCO & 0xC1 are overlong return -1; } else { return nextByte & 0xC000001F; } } else if ((nextByte & 0xF0) == 0xE0) { //2 trailing bytes if (nextByte == (byte) 0xE0) { //possibly overlong return nextByte & 0xA000000F; } else if (nextByte == (byte) 0xED) { //possibly surrogate return nextByte & 0xB000000F; } else { return nextByte & 0x9000000F; } } else if ((nextByte & 0xFC) == 0xF0) { //3 trailing bytes if (nextByte == (byte) 0xF0) { //possibly overlong return nextByte & 0x80000007; } else { return nextByte & 0xE0000007; } } else if (nextByte == (byte) 0xF4) { //3 trailing bytes, possibly undefined return nextByte & 0xD0000007; } else { return -1; } case 0xE0000000: //3rd-to-last continuation byte return (nextByte & 0xC0) == 0x80 ? currentState << 6 | nextByte & 0x9000003F : -1; case 0x80000000: //3rd-to-last continuation byte, check overlong return (nextByte & 0xE0) == 0xA0 || (nextByte & 0xF0) == 0x90 ? currentState << 6 | nextByte & 0x9000003F : -1; case 0xD0000000: //3rd-to-last continuation byte, check undefined return (nextByte & 0xF0) == 0x80 ? currentState << 6 | nextByte & 0x9000003F : -1; case 0x90000000: //2nd-to-last continuation byte return (nextByte & 0xC0) == 0x80 ? currentState << 6 | nextByte & 0xC000003F : -1; case 0xA0000000: //2nd-to-last continuation byte, check overlong return (nextByte & 0xE0) == 0xA0 ? currentState << 6 | nextByte & 0xC000003F : -1; case 0xB0000000: //2nd-to-last continuation byte, check surrogate return (nextByte & 0xE0) == 0x80 ? currentState << 6 | nextByte & 0xC000003F : -1; case 0xC0000000: //last continuation byte return (nextByte & 0xC0) == 0x80 ? currentState << 6 | nextByte & 0x3F : -1; default: return -1; } } |
自动检测编码
如果您的输入流是使用ASCII或ISO-8859-1或UTF-8编码的,但您不确定是哪种,那么我们可以使用与上一种方法类似的方法,但使用附加的编码检测组件在返回字符串之前自动检测编码。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | public static String autoDetect(InputStream is) throws IOException { StringBuilder chars = new StringBuilder(Math.max(is.available(), 4096)); byte[] buffer = new byte[4096]; int n; int state = 0; boolean ascii = true; while ((n = is.read(buffer)) != -1) { for (int i = 0; i < n; i++) { if ((state = nextStateUtf8(state, buffer[i])) > 0x7F) ascii = false; chars.append((char)(buffer[i] & 0xFF)); } } if (ascii || state < 0) { //probably not UTF-8 return chars.toString(); } //probably UTF-8 int pos = 0; char[] charBuf = new char[2]; for (int i = 0, len = chars.length(); i < len; i++) { if ((state = nextStateUtf8(state, (byte)chars.charAt(i))) >= 0) { boolean hi = Character.toChars(state, charBuf, 0) == 2; chars.setCharAt(pos++, charBuf[0]); if (hi) { chars.setCharAt(pos++, charBuf[1]); } } } return chars.substring(0, pos); } |
如果您的输入流的编码既不是ISO-8859-1,也不是ASCII,也不是UTF-8,那么我将遵从已经存在的其他答案。
以下内容并没有解决最初的问题,而是一些回答。
一些反应表明了形式的循环
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或
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第一个表单通过在封闭范围中声明一个变量"read"来污染封闭范围的命名空间,该变量将不会用于for循环之外的任何内容。第二个窗体与readline()调用重复。
这里有一个更简洁的方法来编写Java中的这种循环。原来for循环中的第一个子句不需要实际的初始值设定项值。这将变量"line"的范围保持在for循环的主体中。更优雅!我没见过任何人在任何地方使用过这个表单(几年前的一天我随机发现了它),但我一直在使用它。
1 2 3 |
1 2 3 4 | InputStreamReader i = new InputStreamReader(s); BufferedReader str = new BufferedReader(i); String msg = str.readLine(); System.out.println(msg); |
这是你的
转换输入流到弦乐的方法
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | public static String getStringFromInputStream(InputStream inputStream) { BufferedReader bufferedReader = null; StringBuilder stringBuilder = new StringBuilder(); String line; try { bufferedReader = new BufferedReader(new InputStreamReader( inputStream)); while ((line = bufferedReader.readLine()) != null) { stringBuilder.append(line); } } catch (IOException e) { logger.error(e.getMessage()); } finally { if (bufferedReader != null) { try { bufferedReader.close(); } catch (IOException e) { logger.error(e.getMessage()); } } } return stringBuilder.toString(); } |
用途:
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这个问题的解决方案并不是最简单的,但是由于没有提到NIO流和通道,这里介绍了一个使用NIO通道和ByteBuffer将流转换为字符串的版本。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | public static String streamToStringChannel(InputStream in, String encoding, int bufSize) throws IOException { ReadableByteChannel channel = Channels.newChannel(in); ByteBuffer byteBuffer = ByteBuffer.allocate(bufSize); ByteArrayOutputStream bout = new ByteArrayOutputStream(); WritableByteChannel outChannel = Channels.newChannel(bout); while (channel.read(byteBuffer) > 0 || byteBuffer.position() > 0) { byteBuffer.flip(); //make buffer ready for write outChannel.write(byteBuffer); byteBuffer.compact(); //make buffer ready for reading } channel.close(); outChannel.close(); return bout.toString(encoding); } |
下面是一个如何使用它的示例:
1 2 3 4 | try (InputStream in = new FileInputStream("/tmp/large_file.xml")) { String x = streamToStringChannel(in,"UTF-8", 1); System.out.println(x); } |
对于大型文件,此方法的性能应该很好。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | InputStream inputStream = null; BufferedReader bufferedReader = null; try { BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream)); String stringBuilder = new StringBuilder(); String content; while((content = bufferedReader.readLine()) != null){ stringBuilder.append(content); } System.out.println("content of file::" + stringBuilder.toString()); } catch (IOException e) { e.printStackTrace(); }finally{ if(bufferedReader != null){ try{ bufferedReader.close(); }catch(IoException ex){ ex.printStackTrace(); } |
在SDKSAMPsANDROID-19 连接性 NETWorksNo.NETWorkCopyStaseSrcMadiajavacom示例 Android ETWorkSnutsMadiActuv.java中,Apache许可证、2版和谷歌编写了Java。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | /** Reads an InputStream and converts it to a String. * @param stream InputStream containing HTML from targeted site. * @param len Length of string that this method returns. * @return String concatenated according to len parameter. * @throws java.io.IOException * @throws java.io.UnsupportedEncodingException */ private String readIt(InputStream stream, int len) throws IOException, UnsupportedEncodingException { Reader reader = null; reader = new InputStreamReader(stream,"UTF-8"); char[] buffer = new char[len]; reader.read(buffer); return new String(buffer); } |
对于这个问题,我建议使用StringWriter类。
1 2 3 | StringWriter wt= new StringWriter(); IOUtils.copy(inputStream, wt, encoding); String st= wt.toString(); |
还可以从特定资源路径输入:
1 2 3 4 5 6 7 8 9 10 | public static InputStream getResourceAsStream(String path) { InputStream myiInputStream = ClassName.class.getResourceAsStream(path); if (null == myiInputStream) { mylogger.info("Can't find path =", path); } return myiInputStream; } |
To get inputstream from a specific path:
1 2 3 4 5 6 7 8 9 |
我已经创建了这个代码,并且它可以工作。不需要外部插件。
有将字符串转换为流,将流转换为字符串…
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 | import java.io.ByteArrayInputStream; import java.io.InputStream; public class STRINGTOSTREAM { public static void main(String[] args) { String text ="Hello Bhola..! My Name Is Kishan"; InputStream strm = new ByteArrayInputStream(text.getBytes()); // Convert String to Stream String data = streamTostring(strm); System.out.println(data); } static String streamTostring(InputStream stream) { String data =""; try { StringBuilder stringbuld = new StringBuilder(); int i; while ((i=stream.read())!=-1) { stringbuld.append((char)i); } data = stringbuld.toString(); } catch(Exception e) { data ="No data Streamed."; } return data; } |
注:这可能不是一个好主意。这一方法使用的回归和Thus将击中一个EDOCX1&2。
1 2 3 4 | public String read (InputStream is) { byte next = is.read(); return next == -1 ?"" : next + read(is); // Recursive part: reads next byte recursively } |
请不要低估这一点,因为这是一个糟糕的使用选择;这是最有创意的:)
我有log4j可用,所以我可以使用org.apache.log4j.lf5.util.streamutils.get bytes获取字节,我可以使用字符串ctor将其转换为字符串。
1 2 3 4 5 6 7 | InputStream IS=new URL("http://www.petrol.si/api/gas_prices.json").openStream(); ByteArrayOutputStream BAOS=new ByteArrayOutputStream(); IOUtils.copy(IS, BAOS); String d= new String(BAOS.toByteArray(),"UTF-8"); System.out.println(d); |
首先,您必须知道要转换的字符串的编码。由于
1 2 3 4 5 |
如果
快速简便:
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