從Java類調用servlet

Question

在測試簡單Java類中調用servlet時遇到問題。 我想將參數與Servlet一起傳遞，該方法將為POST。 如何實現？

在搜索答案時，我看到有人推薦了HTTPClient。 但是，只是想知道是否有避免這種情況的方法。

Answer 1

您要做的就是請求一個URL。 像平常一樣放置所有名稱，值對，並在其上打開流。

這里是示例代碼：

import java.io.*; 
import javax.servlet.http.*; 
import javax.servlet.*;

public class SpecialServlet extends HttpServlet 
{

public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException
{ 
    PrintWriter out = res.getWriter(); 
    out.println ("Hello " + req.getParameter("name") + ", this is SpecialServlet!"); 
    out.close(); 
}
} 

Java程序：

import java.net.*; 
import java.io.*; 

public class CmdLineApplication
{
public static void main (String args[])
{
String line;
try
{
URL url = new URL( "http://127.0.0.1/servlet/special?name=CmdLineApplication" );
BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
line = in.readLine();
System.out.println( line );
in.close();
}
catch (Exception e)
{
e.printStackTrace();
}
}
}

將servlet .class文件放在servlet引擎的WEB-INF/classes目錄中。 按常規方式在命令行上運行另一個類：

java CmdLineApplication

您應該看到servlet中的字符串

Answer 2

Servlet容器負責初始化和調用Servlet。 您不能直接調用servlet類。

要發布請求，可以使用HttpClient。

Apache HTTP客戶端

或者您可以使用

URLConnection的

Answer 3

使用以下代碼。使用此代碼，您還可以維護會話。

package webapp;
import org.apache.http.client.HttpClient;
import org.apache.http.impl.client.DefaultHttpClient;


public class HttpClientSingleton {
    public static HttpClientSingleton mSingleton = null;

    public static HttpClient mHttpClient = null;

    //constructor
    private HttpClientSingleton(){
    mHttpClient = new DefaultHttpClient();
    }

    public static HttpClientSingleton getInstance(){
    if( mSingleton == null ){
        mSingleton = new HttpClientSingleton();
    }
    return mSingleton;
    }



}

jsp file:

<%
try{
    int i=0;
String sid = "ED6379C8FDDB801EB970BBDE55E5732D"; 
HttpClientSingleton h1 = HttpClientSingleton.getInstance();
HttpClient client= h1.mHttpClient;


HttpPost responses = new HttpPost("http://localhost:8080/docinbangalore/Billing_address_display?sid="+sid+"");
try {

    HttpResponse respons = client.execute(responses);
    BufferedReader rd = new BufferedReader(new InputStreamReader(respons.getEntity().getContent()));
    String line = "";
    out.println(line = rd.readLine());
    while ((line = rd.readLine()) != null) {
     out.println(line);

    }
  } catch (IOException e) {
    e.printStackTrace();
  }}
catch(Exception e)
{
    out.println(e);
}

%>