筆記：Jakarta HttpClient library (Notes: Jakarta HttpClient library)

1. 需要四個Jar檔：
   • commons-httpclient.jar
   • commons-lang.jar
   • commons-logging.jar
   • commons-codec.jar
2. 簡單範例：
   

   
   import  org.apache.commons.httpclient.HttpClient;
   import  org.apache.commons.httpclient.methods.GetMethod;
   
   public class test{
   public static void main(String[] args)
   {
   try{
   HttpClient client=new HttpClient();
   GetMethod method=new GetMethod("http://www.hinet.net");
   int resultCode=client.executeMethod(method);
   if(resultCode==200)
   System.out.println(method.getResponseAsString());
   }catch(Exception e)
   {}
   }
   }
   

3. HttpClient類別依賴
• HttpConnectionManager介面
• SimpleHttpConnectionManager
• MultithreadedConnectionManager：需要同時做多個連結，預設連線pool是每個host有兩個，可調整最大數為20
  
• HttpClientParams類別
  
4. HttpMethod-->HttpMethodBase --> GetMethod、PostMethod等。(位於org.apache.commons.httpclient.methods)
5. org.apache.commons.httpclient.auth.AuthScheme的實作有：
• BasicScheme
• DigestScheme
• NTLMScheme
6. AuthState:
   
• 提供authentication處理狀態
• 更換authentication scheme
7. AuthPolicy
8. CredentialsProvider:
• 用來向使用者要求憑證
9. AuthChallengeParser、AuthChallengeProcessor：
• 在authentication處理中解析response header
• 處理在header中的盤問(challenge)
10. authendication處理相關Exception:
• AuthChallengeException
• MalformedChallengeException
• InvalidCredentialsException
• CredentialsNotAvaliableException
11. org.apache.commons.httpclient.cookie package裡包含用來處理在HttpClient物件裡heder的cookie。
12. org.apache.commons.httpclient.params裡包含有許多HttpClient重要物件的參數，比如說HttpClientParams就是用來設定HttpClient類別物件的類別。
13. 以下程式碼，可將送出的request中header的browser資訊修改掉：
    

    
    HttpClient client=new HttpClient();
    client.getParams().setParameter("http.useragent", "java browser");

14. 
    用GetMethod取回GIF圖檔：
    



import java.io.FileOutputStream;

import org.apache.commons.httpclient.HostConfiguration;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.URI;
import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.protocol.Protocol;


public class test {


public static void main(String[] args) {
try {
HttpClient client=new HttpClient();
client.getParams().setParameter("http.useragent", "java browser");
GetMethod method=new GetMethod();
method.setURI(new URI("http://tw.yimg.com/i/tw/dictionary/masthead_logo.gif"));
HostConfiguration hostConfig=new HostConfiguration();
hostConfig.setHost("tw.yimg.com",null,80,Protocol.getProtocol("http"));
int result=client.executeMethod(hostConfig,method);
System.out.printf("result code=%d",result);
byte[] gif=method.getResponseBody();
FileOutputStream fos=new FileOutputStream("c:\\image.gif");
fos.write(gif);
fos.close();
} catch (Exception e) {
// TODO: handle exception
}


}

}


在這個範例程式，如果要抓下來的圖檔很大，可以用method.getResponseBodyAsStream()取得InputStream後直接寫入檔案，就不用放在記憶體中了。

15. 上面都是用GetMethod執行，可改用PostMethod，而原本給GetMethod的建構子或setUrl方法的字串中的參數，可用PostMethod物件的addParameter( )即可。
16. 若要以HttpClient做上傳資料動作，可改用MultiPartMethod物件。
17. PutMethod主要用來把檔案放上server，DeleteMethod則相反。
18. HttpClient預設使用SimpleHttpConnectionManager，若需同時發出多個作業，要改用MultiThreadedHttpConnectionManager。
19. multiThread範例：
    

    
    import java.io.BufferedOutputStream;
    import java.io.FileOutputStream;
    import java.io.InputStream;
    
    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.HttpConnectionParams;
    
    
    public class MultiThread extends Thread {
    
    private HttpClient client;
    private GetMethod method;
    
    public MultiThread(HttpClient client,GetMethod method)
    {
    this.client=client;
    this.method=method;
    }
    
    public static void main(String[] args) {
    MultiThreadedHttpConnectionManager mcm=new MultiThreadedHttpConnectionManager();
    HttpConnectionManagerParams params=new HttpConnectionManagerParams();
    params.setDefaultMaxConnectionsPerHost(10);
    mcm.setParams(params);
    
    HttpClient client=new HttpClient(mcm);
    GetMethod method1=new GetMethod("http://www.sun.com/images/l2/l2_phone_pda.gif");
    GetMethod method2=new GetMethod("http://www.sun.com/images/l2/l2_swingap.gif");
    GetMethod method3=new GetMethod("http://java.sun.com/javase/images/dukejdk6_100x88.gif");
    
    new MultiThread(client,method1).start();
    new MultiThread(client,method2).start();
    new MultiThread(client,method3).start();
    }
    
    @Override
    public void run() {
    try{
    client.executeMethod(method);
    
    String filePath="c:\\"+method.getURI().getName();
    InputStream input=method.getResponseBodyAsStream();
    BufferedOutputStream bos=new BufferedOutputStream(new FileOutputStream(filePath));
    int data;
    while((data=input.read())>=0)
     bos.write(data);
    
    input.close();
    bos.close();
    
    }catch(Exception e)
    {
    System.out.println(e);
    }
    }
    
    }
    

    
    
20. HttpClient支援NTLM、Digest、Basic三種authentication。
21. authentication範例1
    

    
               import org.apache.commons.httpclient.*;
               import org.apache.commons.httpclient.auth.*;
               import org.apache.commons.httpclient.method.*;
    
               public class authExam{
                    public static void main(String[] args) throws Exception{
                         HttpClient client=new HttpClient();
                         HostConfiguration host=client.getHostConfiguration();
                         host.setHost(new URI("http://localhost:8080",true));
                 
                         GetMethod method=new GetMethod("protectedArea/protect.jsp");
                         try{
                              int code=client.executeMethod(host,method);
                              if (code==HttpStatus.SC_UNAUTHORIZED)
                                    {
                                      Crenditals cred=new UsernamePasswordCrenditals("tomcat","tomcat");
                                      AuthScope scope=new AuthScope(host.getHost(),host.getPort());
                                      client.getState().setCrentials(scope,cred);
                                      client.executeMethod(host,method);
                                    }
                            }catch(Exception e){}
                    }
               }

22. authentication 範例2
    
           public class authExam2{
                    public static void main(String args[]) throws Exception
                        {
                          HttpClient client=new HttpClient();
                          HostConfiguration host=client.getHostConfiguration();
                          host.setHost(new URI("http://localhost:8080",true));
    
                          Credentials cre=new UsernamePasswordCredential("tomcat","tomcat");
                          AuthoScope scope=new AuthScope(host.getHost(),host.getPort());
                          client.getState().setCredentials(scope,cre);
    
                             try{
                                 client.executeMethod(new GetMethod("http://localhost/protectedArea");)
                             }
                             catch(Exception e){}
                        }
           }

23. 讀取Cookie
    client.getState( ).getCookies( );