struts2声明式异常以及用Filter模拟声明式异常

最新推荐文章于 2020-12-07 10:17:53 发布

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最新推荐文章于 2020-12-07 10:17:53 发布

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分类专栏： struts2 文章标签： filter struts struts2.0 声明式异常全局

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本文介绍如何在Struts2框架中使用声明式异常处理机制简化错误处理流程。通过配置XML文件实现全局异常映射，提高开发效率。同时演示了如何通过过滤器模拟类似的异常处理机制。

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1.声明式异常

struts2支持声明式异常处理，可以再Action中直接抛出异常而交给struts2来处理，当然需要我们在xml文件中配置，由于抛出同样的异常的处理方法通常都一样，所以如果能在xml中配置全局异常，将会使得开发便捷性大大提高。

例如：

Action.java

import com.opensymphony.xwork2.ActionSupport;

public class TestAction1 extends ActionSupport {
	
	@Override
	public String execute() throws Exception {
		System.out.println("TestAction1 execute....");
		int i=1/0;
		return SUCCESS;
	}
}

struts.xml

<struts>
	<constant name="struts.enable.DynamicMethodInvocation" value="false" />
    	<constant name="struts.devMode" value="true" />   
 	<package name="default" namespace="/" extends="struts-default">
 	 	<action name="test1" class="com.zucc.action.TestAction1">
 	 		<result>/index.jsp</result>
 	 		<result name="error">/error.jsp</result>
 	 		<exception-mapping result="error" exception="java.lang.ArithmeticException"/>
 	 	</action>	 	
    </package>
</struts>

分析：TestAction1中抛出ArithmeticException异常，在struts.xml中通过<exception-mapping result="error" exception="java.lang.ArithmeticException"/>获取这个异常，并处理

一般声明式异常都是配置全局异常，这样就不需要在每个action中配置

struts.xml改成

<struts>
	<constant name="struts.enable.DynamicMethodInvocation" value="false" />
    <constant name="struts.devMode" value="true" />
 
 	<package name="default" namespace="/" extends="struts-default">
 		<global-results>
 			<result name="error">/error.jsp</result>
 		</global-results>
 		
 		<global-exception-mappings>
 			<exception-mapping result="error" exception="java.lang.ArithmeticException"/>
 			
 		</global-exception-mappings>
 	 	<action name="test1" class="com.zucc.action.TestAction1">
 	 		<result>/index.jsp</result>
 	 	</action>	 	
    </package>
</struts>

注意：全局result要写在全局异常前面，不然会报错

2.用Filter模拟声明式异常

Servlet.java

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 TestServlet extends HttpServlet{
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		doPost(req, resp);
	}
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		System.out.println("TestServlet .....");
		int i=1/0;
	}
}

Filter.java

Filter.java

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;

public class ExceptionFilter implements Filter {

	@Override
	public void destroy() {
		
	}
	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		System.out.println("ExceptionFilter......come ");
		try {
			chain.doFilter(request, response);
		} 
		catch (Exception e) {
			request.setAttribute("exception", e);
			request.getRequestDispatcher("/error.jsp").forward(request, response);
		}
		System.out.println("ExceptionFilter......back ");
	}

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {

	}

}

web.xml

<servlet>
  	<servlet-name>TestServlet</servlet-name>
  	<servlet-class>com.zucc.servlet.TestServlet</servlet-class>
  </servlet>
  
  <servlet-mapping>
  	<servlet-name>TestServlet</servlet-name>
  	<url-pattern>/test</url-pattern>
  </servlet-mapping>
  
  <filter>
  	<filter-name>ExceptionFilter</filter-name>
  	<filter-class>com.zucc.filter.ExceptionFilter</filter-class>
  </filter>
  
  <filter-mapping>
  	<filter-name>ExceptionFilter</filter-name>
  	<url-pattern>/*</url-pattern>
  </filter-mapping>

分析：在servlet中抛出异常，在web.xml中截获异常，跳转到Filter处理