声明式的异常处理

上一篇文章曾说到自动式异常处理，但是，在项目开发的过程中，是不用的，哈哈
因为：
1. 多参时无法实现
2.要为不同类型的异常坐配置，处理量太大
在项目开发的过程中，一般是用一个统一的异常类来进行异常处理
1.定义统一的异常类，这类继承RuntimeException

package com.xwj.oa.utils;

public class SystemException extends RuntimeException {

	private String key;
	private Object[] values;
	public Object[] getValues() {
		return values;
	}
	public String getKey() {
		return key;
	}

	public SystemException() {
		super();	
	}

	public SystemException(String message, Throwable cause) {
		super(message, cause);
	}

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

	public SystemException(Throwable cause) {
		super(cause);
	}
	public SystemException(String message,String key) {
		super(message);	
		this.key = key;
	}
	public SystemException(String message,String key,Object values) {
		super(message);	
		this.key = key;
		this.values = new Object[]{values};
	}
	public SystemException(String message,String key,Object[] values) {
		super(message);	
		this.key = key;
		this.values =values;
	}

}

2.定义相对应的Handler，它继承于ExceptionHandler

package com.xwj.oa.utils;

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

import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionMessage;
import org.apache.struts.action.ExceptionHandler;
import org.apache.struts.config.ExceptionConfig;


public class SystemExceptionHandler extends ExceptionHandler {

	public ActionForward execute(Exception ex, ExceptionConfig ae,
			ActionMapping mapping, ActionForm formInstance,
			HttpServletRequest request, HttpServletResponse response)
			throws ServletException {

if (ex instanceof SystemException) {

			SystemException se = (SystemException) ex;

			String key = se.getKey();
			ActionMessage error = null;

			if (key == null) {
				error = new ActionMessage(ae.getKey(), se.getMessage());
			} else {
				if(se.getValues() != null){
					error = new ActionMessage(key,se.getValues());
				}else{
					error = new ActionMessage(key);
				}

			}

			ActionForward forward = null;
			if (ae.getPath() != null) {
				forward = new ActionForward(ae.getPath());
			} else {
				forward = mapping.getInputForward();
			}

			this.storeException(request, key, error, forward, ae.getScope());

			return forward;
		}


		return super.execute(ex, ae, mapping, formInstance, request, response);
	}

}

3.在sturuts-config.xml中的配置

<global-exceptions>
		<exception key="errors.detail" type="java.lang.Exception" path="/common/exception.jsp" scope="request"  handler="com.xwj.oa.utils.SystemExceptionHandler"/>
	</global-exceptions>

做好以上三部后就可以使用自己所定义的SystemException,例如：
在做机构管理的时候，先判断是否存在子机构，如果存在子机构，就不给删除

if(org.getChildren().size() > 0){
			throw new SystemException("存在子机构，无发删除","xwj.oa.del",new Integer(org.getId()));
		}

xwj.oa.del：是所对应的国际化资源文件中的错误信息xwj.oa.del=can not del,have children!,id is {0}
new Integer(org.getId())：是国际化资源文件的错误信息的参数