4、struts2异常处理及全局异常与结果剖析、struts2模型驱动及分层体系架构
1、我们可以自定义异常，并且指定当异常出现时，转向哪一个处理页面，首先针对LoginAction这个Action来说，在execute（）方法中手工抛出两个异常：
UsernameException和PasswordException，异常定义：
package com.cdtax.exception;
public class UsernameException extends Exception
{
private String message;
public UsernameException(String message)
{
super(message);
this.message = message;
}
public String getMessage()
{
return message;
}
public void setMessage(String message)
{
this.message = message;
}
}
package com.cdtax.exception;
public class PasswordException extends Exception
{
private String message;
public PasswordException(String message)
{
super(message);
this.message = message;
}
public String getMessage()
{
return message;
}
public void setMessage(String message)
{
this.message = message;
}
}
然后配置struts.xml文件：
<action name="aas" class="com.cdtax.struts2.LoginAction"> <exception-mapping result="usernameinvalid" exception="com.cdtax.exception.UsernameException"></exception-mapping> <exception-mapping result="passwordinvalid" exception="com.cdtax.exception.PasswordException"></exception-mapping> <result name="success">/result.jsp</result> <result name="usernameinvalid">/usernameexception.jsp</result> <result name="passwordinvalid">/passwordexception.jsp</result> </action>
增加了两个exception-mapping和两个result
然后创建两个异常的处理页面usernameexception.jsp和passwordexception.jsp，这样当用户名抛出异常时，页面转向usernameexception.jsp，密码出现异常时，转向passwordexception.jsp。
2、全局的异常处理和全局的结果
全局的异常处理：struts.xml：
<global-results> <result name="usernameinvalid">/usernameexception.jsp</result> <result name="passwordinvalid">/passwordexception.jsp</result> </global-results> <action name="aas" class="com.cdtax.struts2.LoginAction"> <exception-mapping result="usernameinvalid" exception="com.cdtax.exception.UsernameException"></exception-mapping> <exception-mapping result="passwordinvalid" exception="com.cdtax.exception.PasswordException"></exception-mapping> <result name="success">/result.jsp</result> </action>
这时全局的异常处理：局部的优于全局的，就是说，如果在Action标签中也有<result name="usernameinvalid">/passwordexception.jsp</result>，那么页面将优先转向局部的result指向的页面，这里就是passwordexception.jsp。
全局的异常struts.xml：
<global-results> <result name="usernameinvalid">/usernameexception.jsp</result> <result name="passwordinvalid">/passwordexception.jsp</result> </global-results> <global-exception-mappings> <exception-mapping result="usernameinvalid" exception="com.cdtax.exception.UsernameException"></exception-mapping> <exception-mapping result="passwordinvalid" exception="com.cdtax.exception.PasswordException"></exception-mapping> </global-exception-mappings> <action name="aas" class="com.cdtax.struts2.LoginAction"> <result name="success">/result.jsp</result> </action>
也是局部优于全局的。
我们可以在action中定义异常与结果，也可以定义全局的异常和结果，局部总是优于全局的，如果定义成全局，俺么可以为所有action所共享，而局部的异常与结果只能被当前的action所独享，不能为其他action所共享。
3、struts2应用的分层体系结构：
登录的整个流程程序：
login.jsp：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'login.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<form action="aas.action">
username:<input type="text" name="username"><br>
password:<input type="password" name="password"><br>
age:<input type="text" name="aaa">
date:<input type="text" name="date">
<input type="submit" value="submit">
</form>
</body>
</html>
LoginAction：
package com.cdtax.struts2;
import java.util.Date;
import com.cdtax.exception.PasswordException;
import com.cdtax.exception.UsernameException;
import com.cdtax.service.LoginService;
import com.cdtax.service.impl.LoginServiceImpl;
import com.opensymphony.xwork2.ActionSupport;
public class LoginAction extends ActionSupport
{
private String username;
private String password;
private int age;
private Date date;
private LoginService loginService = new LoginServiceImpl();
public Date getDate()
{
return date;
}
public void setDate(Date date)
{
this.date = date;
}
public int getAge()
{
return age;
}
public void setAge(int age)
{
this.age = age;
}
public String getUsername()
{
return username;
}
public void setUsername(String username)
{
this.username = username;
}
public String getPassword()
{
return password;
}
public void setPassword(String password)
{
this.password = password;
}
public String execute() throws Exception
{
// if(!"hello".equals(username))
// {
// throw new UsernameException("username invalid");
// }
// if(!"world".equals(password))
// {
// throw new PasswordException("password invalid!");
// }
if(this.loginService.isLogin(username, password))
{
return SUCCESS;
}
return INPUT;
}
public String myExecute()
{
System.out.println("myExecute invoke!");
return SUCCESS;
}
}
在这里，action增加了一个成员变量，作为对service的引用，execute方法进行业务逻辑判断，调用此service。
service接口定义对上层的服务：
package com.cdtax.service;
public interface LoginService
{
public boolean isLogin(String username,String password);
}
具体的service实现：
package com.cdtax.service.impl;
import com.cdtax.service.LoginService;
public class LoginServiceImpl implements LoginService
{
@Override
public boolean isLogin(String username, String password)
{
if("hello".equals(username) && "world".equals(password))
{
return true;
}
return false;
}
}
struts.xml：
<action name="aas" class="com.cdtax.struts2.LoginAction"> <result name="success">/result.jsp</result> <result name="input">/login.jsp</result> </action>
定义成功后的转向页面result.jsp。
4、struts2的模型驱动（Model Driven）
相对于上面的action模式，叫做属性驱动（Property Driven）
要想实现模型驱动，我们写的action还需要实现ModelDriven接口。
编写一个bean：Person，作为页面提交参数的对象
package com.cdtax.bean;
import java.util.Date;
public class Person
{
private String username;
private String password;
private int age;
private Date date;
public String getUsername()
{
return username;
}
public void setUsername(String username)
{
this.username = username;
}
public String getPassword()
{
return password;
}
public void setPassword(String password)
{
this.password = password;
}
public int getAge()
{
return age;
}
public void setAge(int age)
{
this.age = age;
}
public Date getDate()
{
return date;
}
public void setDate(Date date)
{
this.date = date;
}
}
编写模型驱动的Action：LoginAction2：
package com.cdtax.struts2;
import com.cdtax.bean.Person;
import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.ModelDriven;
public class LoginAction2 extends ActionSupport implements ModelDriven<Person>
{
private Person person = new Person();
@Override
public Person getModel()
{
return person;
}
@Override
public String execute() throws Exception
{
System.out.println(person.getUsername());
return SUCCESS;
}
}
在struts.xml中添加action：
<action name="login2" class="com.cdtax.struts2.LoginAction2"> <result name="success">/result.jsp</result> </action>
编写登录jsp页面：login.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'login.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<form action="login2a.action">
username:<input type="text" name="username"><br>
password:<input type="password" name="password"><br>
age:<input type="text" name="aaa">
date:<input type="text" name="date">
<input type="submit" value="submit">
</form>
</body>
</html>
编写结果页面result.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'result.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
username:${requestScope.username } <br>
password:${requestScope.password }<br>
age:${requestScope.age }
date:${requestScope.date }
aaa:${requestScope.aaa }
</body>
</html>
属性驱动与模型驱动的比较：
1）属性驱动灵活，准确；模型驱动不灵活，因为很多时候，页面提交过来的参数并不属于模型中的属性，也就是说页面所提交过来的参数与模型中的属性并不一致，这是很常见的情况。
2）模型驱动更加符合面向对象的编程风格，使得我们获得是对象而不是一个一个的离散的值。
小结：推荐使用属性驱动编写Action。