首先定义自己的异常类

package com.langhua.oa.manager;

public class SystemException extends RuntimeException {
	//key值
	private String key;
	//可扩展，提供多个构造方法
	private Object[] values;
		
	public SystemException() {
		super();
	}

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

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

	public SystemException(Throwable cause) {
		super(cause);
	}
	//自己定义的构造方法
	public SystemException(String message,String key){
		super(message);
		this.key = key;
	}
	
	public SystemException(String message,String key,Object value){
		super(message);
		this.key = key;
		this.values = new Object[]{value};
	}
	
	public SystemException(String message,String key,Object[] values){
		super(message);
		this.key = key;
		this.values = values;
	}
	
	public String getKey() {
		return key;
	}

	public Object[] getValues() {
		return values;
	}

}

再定义SystemExceptionHandler extends ExceptionHandler

public class SystemExceptionHandler extends ExceptionHandler {
	//当发生异常的时候会自动调用下面的方法，并传过来里面的参数
	public ActionForward execute(
			Exception ex, 
			ExceptionConfig ae,
			ActionMapping mapping, 
			ActionForm formInstance,
			HttpServletRequest request, 
			HttpServletResponse response)throws ServletException {
		 //创建AcctionForward
		ActionForward forward = null;
		//从ExceptionConfig里面获得path 如path="/common/exception.jsp"
		if(ae.getPath() != null){
			//如果path不为空，就建立相当的forward
			forward = new ActionForward(ae.getPath());
		}else{
			//为空的话就使用默认的
			forward = mapping.getInputForward();
		}
		
		//如果产生的异常是SystemException的一个实例
		if(ex instanceof SystemException){
			SystemException se = (SystemException)ex;
			
			//取出key值
			String key = se.getKey();
			//根据相关的参数创建ActionMessage
			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);
				}
			}
			//是放到request里面还是放到session里面
			this.storeException(request, key, error, forward, ae.getScope());
			//带着参数传到相关的JSP页面
			return forward;
		}
		return super.execute(ex, ae, mapping, formInstance, request, response);
	}
	
}

最后在struts的配置文件上面配置上

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

在程序中的使用

if(xxx.getChildren().size()>0){
	throw new SystemException("不能删除","langhua.error");
}