struts编程式异常--html:error与html:message

struts编程式异常过程:

 截获异常信息;创建异常信息;传递异常信息;转向相应页面

 

<html:errors/>显示异常信息

  

<html:messages id="msg" message="true">
	<bean:write name="msg"/>
</html:messages>

当message="true"时输出的是程序中的message信息,而message为false或空时则默认输出异常信息即与html:error一样

 如下:

package com.lwf.struts.action;

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

import org.apache.struts.action.Action;
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.ActionMessages;

import com.lwf.struts.form.LogonForm;
import com.lwf.struts.util.UserManageEntity;
import com.lwf.struts.util.UserNotFoundException;

public class LogonAction extends Action {

	public ActionForward execute(ActionMapping mapping, ActionForm form,
			HttpServletRequest request, HttpServletResponse response)
			throws Exception {
		
		ActionMessages errors = new ActionMessages();
		ActionForward forward = new ActionForward();
		
		LogonForm logonForm = (LogonForm)form;
		String name = logonForm.getUsername();
		String pwd = logonForm.getPassword();
		
		try {
			UserManageEntity.UserManager(name);
			errors.add("logonerror1", new ActionMessage("error.login.user"," myerrmsg"));
			this.saveMessages(request, errors);
			request.getSession().setAttribute("user", logonForm);
			forward = mapping.findForward("success");
		} catch (UserNotFoundException e) {
			errors.add("logonerror2", new ActionMessage("error.login.again"," error2"));
			this.saveErrors(request, errors);
			forward = mapping.findForward("error");
		}
		
		return forward;
	}

	
}

 

 

注意程序中:

saveMessages与saveErrors两个方法的调用

 

package com.lwf.struts.util;

public class UserManageEntity {

	public static void UserManager(String username) throws UserNotFoundException{
		if(username!=null && !username.equals("admin")){
			throw new UserNotFoundException();
			
		}
	}
}

 

package com.lwf.struts.util;

public class UserNotFoundException extends Exception {

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

 

 

struts还规定在资源文件中定义以下属性

errors.header	= <UL>
errors.prefix	= <LI>
errors.suffix	= </LI>
errors.footer	= </UL>

 

如果连续有多条异常信息那么每一条会显示在LI中,多条信息会显示在UL中.

如果我们想每一条异常信息显示为红色字体那么可以这样做：

errors.header	= <UL>
errors.prefix	= <LI><font color="red">
errors.suffix	= </LI></font>
errors.footer	= </UL>