How to access JSP implicit objects like (request ,

问题:

How to pass JSP implicit objects like (request, response) in Java. I want to access JSP Implicit Objects in Java code. Please suggest how to achieve this?

My Java code is:

package test.here;
import java.sql.*;
import java.util.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.ibm.commerce.server.WcsApp;
import com.ibm.commerce.server.JSPHelper;

public class SomeBean {
  String punchOutRes = null;
  HttpServletResponse response;
  HttpServletRequest request; 

  public String getPunchOutRes() {         
    response.setContentType("text/xml");
    return "testing";      
  } 
}

Here when I am trying to set or get anything in request and response, I get NUllPointerException.

回答1:

You can pass objects to the bean using <jsp:setProperty and EL expressions. You have to modify the bean for getter and setter methods.

public class SomeBean {
  String punchOutRes = null;
  HttpServletResponse response;
  HttpServletRequest request;

  public HttpServletResponse getResponse() {
    return response;
  }

  public void setResponse(HttpServletResponse response) {
    this.response = response;
    try {
      response.getWriter().println("Some Output");
    } catch (IOException e) {
      e.printStackTrace();  
    }
  }

  public HttpServletRequest getRequest() {
    return request;
  }

  public void setRequest(HttpServletRequest request) {
    this.request = request;
  }

  public String getPunchOutRes() {
    response.setContentType("text/xml");
    return "testing";
  }
}

then use in the JSP

<jsp:useBean id="someBean" class="beans.SomeBean" scope="request"/>
<jsp:setProperty name="someBean" property="request" value="${pageContext.request}"/>
<jsp:setProperty name="someBean" property="response" value="${pageContext.response}"/>

回答2:

IMO I don't think it is possible to pass implicit objects directly to java class so but one thing you can do is pass session and request object from servlet to a java class either in some method or in constructor of java class.

Also see this question

回答3:

You would be able to use some servlet class. for instance :

public class ActionServlet extends HttpServlet
{

public ActionServlet()
{ 
  super();
}

protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException,IOException
{
    request.setCharacterEncoding("UTF-8");      
    String action = request.getParameter("action");        

    //do smth. with "action" you are able to use your class "SomeBean"

    response.setContentType("text/plain");
    response.setCharacterEncoding("UTF-8");
    response.sendRedirect(someUrl);                

}
}

you must add into the web.xml following:

 <servlet>
    <description></description>
    <display-name>ActionServlet</display-name>
    <servlet-name>ActionServlet</servlet-name>
    <servlet-class>com.your_package.servlet.ActionServlet</servlet-class>
 </servlet>
 <servlet-mapping>
    <servlet-name>ActionServlet</servlet-name>
    <url-pattern>/Action</url-pattern>
 </servlet-mapping>

"/Action" is your url.

I gave a simple example, I didn't take account the either GET or POST method there. Also I would advise to use JSTL. Using some scriplets in the "view" is bad style of codding:)

However, it's better to use MVC pattern(Spring/Struts).