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1、缘由：我们在做项目中肯定都会遇到自定义业务异常，然后将业务异常信息跳转的统一的信息提示页面的情况，比如我们在struts的时候我们会用到struts的异常处理机制，我们在业务层会跑出我们遇到业务处理异常，然后交由struts处理将提示信息到一个页面进行显示，来提示用户的相关操作，这里我们会根据以上情景设计一下怎么来显示该功能。

2、解决方法：我们的业务异常通常都是抛出的，就是unchecked exception，所以最后总会到达调用该方法的最外层进行捕获，一般我们都会在action中调用我们的业务方法，而业务方法可能会跑出异常，此时我们就可以在此时做些文章了，我们可以利用filter，来捕获我们抛出的异常，然后跳转到一个统一页面，进行信息提示了。

3、具体代码：

①自定义异常类，我想这个就不用多说了，大家都是会的：

BsException.java

package com.ajun.exception;

/**
* 业务异常类
* @author ajun
* @http://blog.csdn.net/ajun_studio
*/
public class BsException extends RuntimeException {

    //异常代码
    private String key;

    private Object[] values;//一些其他信息

    public BsException() {
        super();
    }

    public BsException(String message, Throwable throwable) {
        super(message, throwable);
    }

    public BsException(String message) {
        super(message);
    }

    public BsException(Throwable throwable) {
        super(throwable);
    }

    public BsException(String message,String key){
        super(message);
        this.key = key;
    }

    public BsException(String message,String key,Object value){
        super(message);
        this.key = key;
        this.values = new Object[]{value};
    }

    public BsException(String message,String key,Object[] values){
        super(message);
        this.key = key;
        this.values = values;
    }

    public String getKey() {
        return key;
    }

    public Object[] getValues() {
        return values;
    }
}
package com.ajun.exception;

/**
* 业务异常类
* @author ajun
* @http://blog.csdn.net/ajun_studio
*/
public class BsException extends RuntimeException {

//异常代码
private String key;

private Object[] values;//一些其他信息

public BsException() {
super();
}

public BsException(String message, Throwable throwable) {
super(message, throwable);
}

public BsException(String message) {
super(message);
}

public BsException(Throwable throwable) {
  super(throwable);
}

public BsException(String message,String key){
  super(message);
  this.key = key;
}

public BsException(String message,String key,Object value){
  super(message);
  this.key = key;
  this.values = new Object[]{value};
}

public BsException(String message,String key,Object[] values){
  super(message);
  this.key = key;
  this.values = values;
}

public String getKey() {
return key;
}

public Object[] getValues() {
return values;
}
}
既然要用到filter ，自然少不了实现Filter接口，拦截你想要的请求，然后，就可以捕获异常了，此时你可以对你的chain.doFilter进行try catch，然后判断你想捕获的异常，很简单，请看代码：

package com.ajun.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.ajun.exception.BsException;

/**
* 业务异常过滤器
* @author ajun
* @http://blog.csdn.net/ajun_studio
*/
public class ExceptionFiler implements Filter {

    private String errorPage;//跳转的错误信息页面


    public void destroy() {

    }

    public void doFilter(ServletRequest req, ServletResponse res,
            FilterChain chain) throws IOException, ServletException {

         HttpServletResponse response = (HttpServletResponse) res;
         HttpServletRequest request = (HttpServletRequest) req;
         //捕获你抛出的业务异常
         try {
            chain.doFilter(req, res);
        } catch (RuntimeException e) {
            if(e instanceof BsException){//如果是你定义的业务异常
                request.setAttribute("BsException", e);//存储业务异常信息类
                request.getRequestDispatcher(errorPage).forward(request, response);//跳转到信息提示页面！！
            }
            e.printStackTrace();
        }
    }
       //初始化读取你配置的提示页面路径
    public void init(FilterConfig config) throws ServletException {
        //读取错误信息提示页面路径
        errorPage = config.getInitParameter("errorPage");
        if(null==errorPage || "".equals(errorPage)){
            throw new RuntimeException("没有配置错误信息跳转页面,请再web.xml中进行配置\n<init-param>\n<param-name>errorPage</param-name>\n<param-value>/error.jsp</param-value>\n </init-param>\n路径可以是你自己设定的任何有效路径页面！！");
            //System.out.println("没有配置错误信息跳转页面");
        }
    }

}
package com.ajun.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.ajun.exception.BsException;

/**
* 业务异常过滤器
* @author ajun
* @http://blog.csdn.net/ajun_studio
*/
public class ExceptionFiler implements Filter {

private String errorPage;//跳转的错误信息页面

public void destroy() {

}

public void doFilter(ServletRequest req, ServletResponse res,
FilterChain chain) throws IOException, ServletException {

   HttpServletResponse response = (HttpServletResponse) res;
      HttpServletRequest request = (HttpServletRequest) req;
      //捕获你抛出的业务异常
      try {
   chain.doFilter(req, res);
  } catch (RuntimeException e) {
   if(e instanceof BsException){//如果是你定义的业务异常
    request.setAttribute("BsException", e);//存储业务异常信息类
    request.getRequestDispatcher(errorPage).forward(request, response);//跳转到信息提示页面！！
   }
   e.printStackTrace();
  }
}
       //初始化读取你配置的提示页面路径
public void init(FilterConfig config) throws ServletException {
  //读取错误信息提示页面路径
  errorPage = config.getInitParameter("errorPage");
  if(null==errorPage || "".equals(errorPage)){
   throw new RuntimeException("没有配置错误信息跳转页面,请再web.xml中进行配置\n<init-param>\n<param-name>errorPage</param-name>\n<param-value>/error.jsp</param-value>\n </init-param>\n路径可以是你自己设定的任何有效路径页面！！");
   //System.out.println("没有配置错误信息跳转页面");
  }
}

}

Filter在web.xml中的配置如下：

view plaincopy to clipboardprint?
<filter>
    <filter-name>ExceptionFilter</filter-name>
    <filter-class>com.ajun.filter.ExceptionFiler</filter-class>
    <init-param>
        <param-name>errorPage</param-name>
        <param-value>/error.jsp</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>ExceptionFilter</filter-name>
    <url-pattern>*.do</url-pattern>
</filter-mapping>
<filter>
  <filter-name>ExceptionFilter</filter-name>
  <filter-class>com.ajun.filter.ExceptionFiler</filter-class>
  <init-param>
     <param-name>errorPage</param-name>
     <param-value>/error.jsp</param-value>
     </init-param>
</filter>
<filter-mapping>
  <filter-name>ExceptionFilter</filter-name>
  <url-pattern>*.do</url-pattern>
</filter-mapping>
下面写个servlet ，在请求的时候抛出你定义业务异常来试验一下吧

package com.ajun.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ExServlet extends HttpServlet {


    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        this.doPost(request, response);

    }


    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        TestService t = new TestService();
        t.add();//模拟调用业务层方法，在此方法内抛出异常，此异常会在filter中进行捕获。

    }

}
package com.ajun.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ExServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

this.doPost(request, response);

}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

  TestService t = new TestService();
  t.add();//模拟调用业务层方法，在此方法内抛出异常，此异常会在filter中进行捕获。

}

}
web.xml配置上述servlet

view plaincopy to clipboardprint?
<servlet>
<servlet-name>ExServlet</servlet-name>
<servlet-class>com.ajun.servlet.ExServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>ExServlet</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>ExServlet</servlet-name>
<servlet-class>com.ajun.servlet.ExServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>ExServlet</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
测试时在servlet中被调用的业务类

TestService.java

view plaincopy to clipboardprint?
package com.ajun.servlet;

import com.ajun.exception.BsException;

public class TestService {

    public void add(){

        System.out.println("add () was called!!");
        if(true){
            throw new BsException("in add() throws exception!!");//抛出异常，根据你的业务逻辑
        }
    }
}
package com.ajun.servlet;

import com.ajun.exception.BsException;

public class TestService {

public void add(){

  System.out.println("add () was called!!");
  if(true){
   throw new BsException("in add() throws exception!!");//抛出异常，根据你的业务逻辑
  }
}
}

现在部署项目，在你的浏览器内输入：http://localhost:8080/BsException/ajun.do

成功跳转到error.jsp:显示：in add() throws exception!!

在后台得到：

com.ajun.exception.BsException: in add() throws exception!!
    at com.ajun.servlet.TestService.add(TestService.java:11)
    at com.ajun.servlet.ExServlet.doPost(ExServlet.java:26)
    at com.ajun.servlet.ExServlet.doGet(ExServlet

posted on 2011-12-29 18:20 Eric_jiang 阅读(4773) 评论(0) 编辑收藏所属分类: Java

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