Sevrlet处理异常

 

项目为给客户提供较好的展示，通常会对异常进行统一处理，除去框架处理外，可以采用servlet处理：

1.在web.xml文件中配置异常处理。

<error-page>
          <error-code>404</error-code>
          <location>/common/404.jsp</location>
</error-page>

 

这种方式要为每种异常都一个异常配置，处理比较单一。

2.采用Filter过滤控制统一管理异常。

<filter>
		<filter-name>ExceptionFilter</filter-name>
		<filter-class>com.hsit.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>

	<servlet>
		<servlet-name>ExServlet</servlet-name>
		<servlet-class>com.hsit.ExServlet</servlet-class>
	</servlet>


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

 

/** 
 * 业务异常类 
 */  
public class BsException extends RuntimeException {  
	private static final long serialVersionUID = 6744141471703095812L;

	//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;  
    }  
}  

 

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;


/** 
 * 业务异常过滤器 
 */  
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");   
        }  
    }  
  
}  

 

import java.io.IOException;  
import javax.servlet.ServletException;  
import javax.servlet.http.HttpServlet;  
import javax.servlet.http.HttpServletRequest;  
import javax.servlet.http.HttpServletResponse;  
  
public class ExServlet extends HttpServlet {  
	private static final long serialVersionUID = 2303258011121708614L;


	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。   

    }  
  
}  

 

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
		  }
		 }

}

 

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
  	<title>运行时异常处理</title>
  </head>
  <body>
  	<form action="/ExceptionHandler/exceptionTest.do">
  		<input type="submit" value="测试"></input>
  	</form>
  </body>
</html>

 

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
  	<title>捕获异常</title>
  </head>
  <body>
  	
  </body>
</html>