如果您有java.io.InputStream对象,应该如何处理该对象并生成String?
假设我有一个包含文本数据的InputStream,我想将其转换为String,例如,我可以将其写入日志文件。
获取InputStream并将其转换为字符串的最简单方法是什么?
public String convertStreamToString(InputStream is) {
// ???
}
如果您有java.io.InputStream对象,应该如何处理该对象并生成String?
假设我有一个包含文本数据的InputStream,我想将其转换为String,例如,我可以将其写入日志文件。
获取InputStream并将其转换为字符串的最简单方法是什么?
public String convertStreamToString(InputStream is) {
// ???
}
当前回答
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转换为字符串。(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:
String response;
String url = "www.blah.com/path?key=value";
GetMethod method = new GetMethod(url);
int status = client.executeMethod(method);
1)
response = method.getResponseBodyAsString();
2)
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)
InputStream iStream = method.getResponseBodyAsStream();
StringWriter writer = new StringWriter();
IOUtils.copy(iStream, writer, "UTF-8");
response = writer.toString();
因此,在使用相同的请求/响应数据对每种方法运行了500次测试之后,以下是数字。再次,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向其他人说明这些方法的效率差异。
排名:方法#1进近#3-比#1慢2.6%2号进近——比1号进近慢4.3%
任何这些方法都是获取响应并从中创建字符串的适当解决方案。
其他回答
以下内容并没有回答最初的问题,而是回答了一些问题。
几个回答暗示了这种形式的循环
String line = null;
while((line = reader.readLine()) != null) {
// ...
}
or
for(String line = reader.readLine(); line != null; line = reader.readLine()) {
// ...
}
第一种形式通过在封闭作用域中声明一个变量“read”来污染封闭作用域的命名空间,该变量不会用于for循环之外的任何内容。第二个表单重复readline()调用。
这里有一种用Java编写这种循环的更简洁的方法。事实证明,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循环的主体内。更优雅!我在任何地方都没有看到有人使用这个表单(几年前的一天我随机发现了它),但我一直在使用它。
for (String line; (line = reader.readLine()) != null; ) {
//...
}
我已经写了一个这样的课,所以我想我会和大家分享。有时候,您不想仅仅为了一件事而添加Apache Commons,并且想要比Scanner更笨的东西,它不检查内容。
用法如下
// Read from InputStream
String data = new ReaderSink(inputStream, Charset.forName("UTF-8")).drain();
// Read from File
data = new ReaderSink(file, Charset.forName("UTF-8")).drain();
// Drain input stream to console
new ReaderSink(inputStream, Charset.forName("UTF-8")).drainTo(System.out);
以下是ReaderSink的代码:
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);
}
}
}
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);
如果使用流读取器,请确保在结束时关闭流
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("\n"); // 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trywithresources构造。
/**
* 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("\n"); // append new line to preserve lines
}
return builder.toString();
}
}
使用java 9中支持的java.io.InputStream.transferTo(OutputStream)和ByteArrayOutputStream.toString(String),该字符串采用字符集名称:
public static String gobble(InputStream in, String charsetName) throws IOException {
ByteArrayOutputStream bos = new ByteArrayOutputStream();
in.transferTo(bos);
return bos.toString(charsetName);
}