HttpUrlConnection与HttpClient的认识（七） -HttpClient的线程安全问题

转载自：http://blog.csdn.net/u010248330/article/details/69524542

对于HttpClient的使用，我们在项目中一般会封装成一个工具栏使用，方便调用，在 HttpUrlConnection与HttpClient的认识（四） -HttpClient的封装 这篇博客中，已经说明过了。

上次的封装是没有问题的，我们拿来测试一下。

1、线程安全的封装

package com.httpClient.thread.test;import org.apache.commons.httpclient.*;import org.apache.commons.httpclient.methods.*;import java.io.*;/** *线程安全的封装，因为每次都是重新实例化的HttpClient */public class HttpClientUtil1 {    public static String httpClientGet(String url){        StringBuilder sb =new StringBuilder();        //每次都重新实例化一个httpClient        HttpClient httpClient = new HttpClient();        GetMethod getMethod = new GetMethod(url);        try {             httpClient.executeMethod(getMethod);             InputStream is = getMethod.getResponseBodyAsStream();             BufferedReader dis=new BufferedReader(new InputStreamReader(is,"utf-8"));                String str ="";                                        while((str =dis.readLine())!=null){                 sb.append(str);             }        } catch (Exception e) {             e.printStackTrace();        } finally {            // 关闭连接            getMethod.releaseConnection();        }        return sb.toString();     }}
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开启多线程使用一下这个类：

package com.httpClient.thread.test;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;public class TestHttpClientThreadPro {     private static String url="http://www.baidu.com";     public static void main(String[] args) {         ExecutorService threadPool=Executors.newFixedThreadPool(4);         for ( int i = 0; i < 6; i++) {             threadPool.execute(new Runnable() {                @Override                public void run() {                        HttpClientUtil1.httpClientGet(url);                        System.out.println("=====访问结果==="+result);            }         });         }     }}
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我们可以访问一下是完全没有问题的。

实际在我们的项目中，会经常将HttpClient封装成单例的形式，因为我们在多处需要进行HTTP通信发送网络请求时，没必要为每个请求都创建一个新的HttpClient，一个HttpClient就可以了。 
但是在多线程情况下访问是出问题的，那我们看看这种情况：

2.线程不安全的封装

package com.httpClient.thread.test;import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import org.apache.commons.httpclient.HttpClient;import org.apache.commons.httpclient.methods.GetMethod;import org.apache.commons.httpclient.params.HttpMethodParams;/** *线程不安全，只有唯一的一个实例 */public class HttpClientUtil2 {    //唯一的HttpClient实例    private static HttpClient httpClient=new HttpClient();    public static String httpClientGet(String url){        StringBuilder sb =new StringBuilder();        GetMethod getMethod = new GetMethod(url);        try {            httpClient.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, "utf-8");            httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(3000);            httpClient.getHttpConnectionManager().getParams().setSoTimeout(3000);            //httpClient永远是同一个            int statusCode = httpClient.executeMethod(getMethod);            if (statusCode==200) {                InputStream is = getMethod.getResponseBodyAsStream();                BufferedReader dis=new BufferedReader(new InputStreamReader(is,"utf-8"));                   String str ="";                                           while((str =dis.readLine())!=null){                    sb.append(str);                    sb.append("\r\n");                 }               }        } catch (Exception e) {            e.printStackTrace();        }finally{            getMethod.releaseConnection();        }        return sb.toString();    }}
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在测试的TestHttpClientThreadPro类中修改为

      HttpClientUtil2.httpClientGet(url);

运行代码：

2017-4-7 10:48:25 org.apache.commons.httpclient.SimpleHttpConnectionManager getConnectionWithTimeout警告: SimpleHttpConnectionManager being used incorrectly.  Be sure that HttpMethod.releaseConnection() is always called and that only one thread and/or method is using this connection manager at a time.2017-4-7 10:48:25 org.apache.commons.httpclient.SimpleHttpConnectionManager getConnectionWithTimeout警告: SimpleHttpConnectionManager being used incorrectly.  Be sure that HttpMethod.releaseConnection() is always called and that only one thread and/or method is using this connection manager at a time.2017-4-7 10:48:25 org.apache.commons.httpclient.SimpleHttpConnectionManager getConnectionWithTimeout警告: SimpleHttpConnectionManager being used incorrectly.  Be sure that HttpMethod.releaseConnection() is always called and that only one thread and/or method is using this connection manager at a time.java.net.SocketException: Socket Closed    at java.net.SocketInputStream.socketRead0(Native Method)    at java.net.SocketInputStream.read(SocketInputStream.java:129)    at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)    at java.io.BufferedInputStream.read(BufferedInputStream.java:237)    at org.apache.commons.httpclient.HttpParser.readRawLine(HttpParser.java:78)    at org.apache.commons.httpclient.HttpParser.readLine(HttpParser.java:106)    at org.apache.commons.httpclient.HttpConnection.readLine(HttpConnection.java:1116)    at org.apache.commons.httpclient.HttpMethodBase.readStatusLine(HttpMethodBase.java:1973)    at org.apache.commons.httpclient.HttpMethodBase.readResponse(HttpMethodBase.java:1735)    at org.apache.commons.httpclient.HttpMethodBase.execute(HttpMethodBase.java:1098)    at org.apache.commons.httpclient.HttpMethodDirector.executeWithRetry(HttpMethodDirector.java:398)    at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:171)    at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:397)    at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:323)    at com.httpClient.thread.test.HttpClientUtil2.httpClientGet(HttpClientUtil2.java:24)    at com.httpClient.thread.test.TestHttpClientThreadPro$1.run(TestHttpClientThreadPro.java:18)    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)    at java.lang.Thread.run(Thread.java:662)org.apache.commons.httpclient.ProtocolException: Unable to parse header: e8anpt    at org.apache.commons.httpclient.HttpParser.parseHeaders(HttpParser.java:202)    at org.apache.commons.httpclient.HttpMethodBase.readResponseHeaders(HttpMethodBase.java:1935)    at org.apache.commons.httpclient.HttpMethodBase.readResponse(HttpMethodBase.java:1737)    at org.apache.commons.httpclient.HttpMethodBase.execute(HttpMethodBase.java:1098)    at org.apache.commons.httpclient.HttpMethodDirector.executeWithRetry(HttpMethodDirector.java:398)    at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:171)    at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:397)    at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:323)    at com.httpClient.thread.test.HttpClientUtil2.httpClientGet(HttpClientUtil2.java:24)    at com.httpClient.thread.test.TestHttpClientThreadPro$1.run(TestHttpClientThreadPro.java:18)    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)    at java.lang.Thread.run(Thread.java:662)java.io.IOException: Stream closed    at java.io.BufferedInputStream.getBufIfOpen(BufferedInputStream.java:145)    at java.io.BufferedInputStream.fill(BufferedInputStream.java:189)    at java.io.BufferedInputStream.read(BufferedInputStream.java:237)    at org.apache.commons.httpclient.HttpParser.readRawLine(HttpParser.java:78)    at org.apache.commons.httpclient.HttpParser.readLine(HttpParser.java:106)    at org.apache.commons.httpclient.HttpConnection.readLine(HttpConnection.java:1116)    at org.apache.commons.httpclient.HttpMethodBase.readStatusLine(HttpMethodBase.java:1973)    at org.apache.commons.httpclient.HttpMethodBase.readResponse(HttpMethodBase.java:1735)    at org.apache.commons.httpclient.HttpMethodBase.execute(HttpMethodBase.java:1098)    at org.apache.commons.httpclient.HttpMethodDirector.executeWithRetry(HttpMethodDirector.java:398)    at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:171)    at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:397)    at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:323)    at com.httpClient.thread.test.HttpClientUtil2.httpClientGet(HttpClientUtil2.java:24)    at com.httpClient.thread.test.TestHttpClientThreadPro$1.run(TestHttpClientThreadPro.java:18)    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)    at java.lang.Thread.run(Thread.java:662)java.lang.IllegalStateException: Unexpected release of an unknown connection.    at org.apache.commons.httpclient.SimpleHttpConnectionManager.releaseConnection(SimpleHttpConnectionManager.java:225)    at org.apache.commons.httpclient.HttpConnection.releaseConnection(HttpConnection.java:1179)    at org.apache.commons.httpclient.HttpMethodBase.ensureConnectionRelease(HttpMethodBase.java:2430)    at org.apache.commons.httpclient.HttpMethodBase.responseBodyConsumed(HttpMethodBase.java:2422)    at org.apache.commons.httpclient.HttpMethodBase$1.responseConsumed(HttpMethodBase.java:1892)    at org.apache.commons.httpclient.AutoCloseInputStream.notifyWatcher(AutoCloseInputStream.java:198)    at org.apache.commons.httpclient.AutoCloseInputStream.checkClose(AutoCloseInputStream.java:170)    at org.apache.commons.httpclient.AutoCloseInputStream.read(AutoCloseInputStream.java:109)    at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:264)    at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:306)    at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:158)    at java.io.InputStreamReader.read(InputStreamReader.java:167)    at java.io.BufferedReader.fill(BufferedReader.java:136)    at java.io.BufferedReader.readLine(BufferedReader.java:299)    at java.io.BufferedReader.readLine(BufferedReader.java:362)    at com.httpClient.thread.test.HttpClientUtil2.httpClientGet(HttpClientUtil2.java:29)    at com.httpClient.thread.test.TestHttpClientThreadPro$1.run(TestHttpClientThreadPro.java:18)    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)    at java.lang.Thread.run(Thread.java:662)2017-4-7 10:48:25 org.apache.commons.httpclient.SimpleHttpConnectionManager getConnectionWithTimeout警告: SimpleHttpConnectionManager being used incorrectly.  Be sure that HttpMethod.releaseConnection() is always called and that only one thread and/or method is using this connection manager at a time.Exception in thread "pool-1-thread-1" java.lang.IllegalStateException: Unexpected release of an unknown connection.    at org.apache.commons.httpclient.SimpleHttpConnectionManager.releaseConnection(SimpleHttpConnectionManager.java:225)    at org.apache.commons.httpclient.HttpConnection.releaseConnection(HttpConnection.java:1179)    at org.apache.commons.httpclient.HttpMethodBase.ensureConnectionRelease(HttpMethodBase.java:2430)    at org.apache.commons.httpclient.HttpMethodBase.releaseConnection(HttpMethodBase.java:1186)    at com.httpClient.thread.test.HttpClientUtil2.httpClientGet(HttpClientUtil2.java:37)    at com.httpClient.thread.test.TestHttpClientThreadPro$1.run(TestHttpClientThreadPro.java:18)    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)    at java.lang.Thread.run(Thread.java:662)java.lang.IllegalStateException: Connection is not open    at org.apache.commons.httpclient.HttpConnection.assertOpen(HttpConnection.java:1277)    at org.apache.commons.httpclient.HttpConnection.readLine(HttpConnection.java:1115)    at org.apache.commons.httpclient.HttpMethodBase.readStatusLine(HttpMethodBase.java:1973)    at org.apache.commons.httpclient.HttpMethodBase.readResponse(HttpMethodBase.java:1735)    at org.apache.commons.httpclient.HttpMethodBase.execute(HttpMethodBase.java:1098)    at org.apache.commons.httpclient.HttpMethodDirector.executeWithRetry(HttpMethodDirector.java:398)    at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:171)    at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:397)    at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:323)    at com.httpClient.thread.test.HttpClientUtil2.httpClientGet(HttpClientUtil2.java:24)    at com.httpClient.thread.test.TestHttpClientThreadPro$1.run(TestHttpClientThreadPro.java:18)    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)    at java.lang.Thread.run(Thread.java:662)org.apache.commons.httpclient.ProtocolException: Unable to parse header: T 0 K    at org.apache.commons.httpclient.HttpParser.parseHeaders(HttpParser.java:202)    at org.apache.commons.httpclient.HttpMethodBase.readResponseHeaders(HttpMethodBase.java:1935)    at org.apache.commons.httpclient.HttpMethodBase.readResponse(HttpMethodBase.java:1737)    at org.apache.commons.httpclient.HttpMethodBase.execute(HttpMethodBase.java:1098)    at org.apache.commons.httpclient.HttpMethodDirector.executeWithRetry(HttpMethodDirector.java:398)    at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:171)    at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:397)    at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:323)    at com.httpClient.thread.test.HttpClientUtil2.httpClientGet(HttpClientUtil2.java:24)    at com.httpClient.thread.test.TestHttpClientThreadPro$1.run(TestHttpClientThreadPro.java:18)    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)    at java.lang.Thread.run(Thread.java:662)
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我们发现代码报错了，说明这是线程不安全的一种封装。。

针对这种情况，HttpClient提供了MultiThreadedHttpConnectionManager解决这种线程不安全的请求。使用起来很简单：

MultiThreadedHttpConnectionManager connectionManager =                 new MultiThreadedHttpConnectionManager();          HttpClient httpClient= new HttpClient(connectionManager);
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这样封装的httpClient使用起来就没问题了。

3.MultiThreadedHttpConnectionManager解决线程安全的问题

package com.httpClient.thread.test;import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import org.apache.commons.httpclient.HttpClient;import org.apache.commons.httpclient.MultiThreadedHttpConnectionManager;import org.apache.commons.httpclient.methods.GetMethod;import org.apache.commons.httpclient.params.HttpConnectionManagerParams;import org.apache.commons.httpclient.params.HttpMethodParams;/** * 线程安全的封装 */public class HttpClientUtil3 {    private static MultiThreadedHttpConnectionManager connectionManager;    private static HttpClient httpClient;    private static int maxHostConnections = 10;    private static int maxTotalConnections = 20;    static {        connectionManager = new MultiThreadedHttpConnectionManager();        HttpConnectionManagerParams params = new HttpConnectionManagerParams();        params.setDefaultMaxConnectionsPerHost(maxHostConnections);        params.setMaxTotalConnections(maxTotalConnections);        connectionManager.setParams(params);        httpClient = new HttpClient(connectionManager);        httpClient.getParams().setParameter(HttpMethodParams.HTTP_CONTENT_CHARSET, "UTF-8");    }    public static String httpClientGet(String url){        StringBuilder sb =new StringBuilder();        GetMethod getMethod = new GetMethod(url);        try {            //httpClient永远是同一个            int statusCode = httpClient.executeMethod(getMethod);            if (statusCode==200) {                InputStream is = getMethod.getResponseBodyAsStream();                BufferedReader dis=new BufferedReader(new InputStreamReader(is,"utf-8"));                   String str ="";                                           while((str =dis.readLine())!=null){                    sb.append(str);                    sb.append("\r\n");                 }               }        } catch (Exception e) {            e.printStackTrace();        }finally{            getMethod.releaseConnection();        }        return sb.toString();    }}
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在测试的TestHttpClientThreadPro类中修改为

      HttpClientUtil3.httpClientGet(url);

运行代码没有任何问题。