手动创建Servlet异常处理

import javax.servlet.*;
import java.io.IOException;
import java.io.PrintWriter;

public class ExceptionServlet implements Servlet {

    @Override
    public void init(ServletConfig servletConfig) {

    }

    @Override
    public ServletConfig getServletConfig() {
        return null;
    }

    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        throw new ServletException("hello");  
    }

    @Override
    public String getServletInfo() {
        return null;
    }

    @Override
    public void destroy() {

    }
}

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

// 扩展 HttpServlet 类
public class ErrorHandler extends HttpServlet {
 
  // 处理 GET 方法请求的方法
  public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException
  {
      PrintWriter out = response.getWriter();
      // 分析 Servlet 异常       
      Throwable throwable = (Throwable)request.getAttribute("javax.servlet.error.exception");
      Integer statusCode = (Integer)request.getAttribute("javax.servlet.error.status_code");
      String servletName = (String)request.getAttribute("javax.servlet.error.servlet_name");
      String requestUri = (String)request.getAttribute("javax.servlet.error.request_uri");

      if (throwable != null){
         out.println("Exception Type : " + throwable.getClass( ).getName( ));
         out.println("The exception message: " + throwable.getMessage( ));
      }
      if (statusCode != null){
         out.println("The status code : " + statusCode);
      }
      out.println("Servlet Name : " + servletName);
      out.println("The request URI: " + requestUri);
         
  }
  // 处理 POST 方法请求的方法
  public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
     doGet(request, response);
  }
}