重要特性总结
- Struts2 的类型转换，对于 8 个原生数据类型以及 Date，String 等常见类型，Struts2 可以使内建的类型转换器实现自动的转换；但对于自定义的对象类型来说，需要我们自己指定类型转换的方式，即自定义类型转换器。
- 对于自定义类型的转换器来说，需要提供三个信息：Action 的名字、Action 中待转换的属性名以及该属性对应的类型转换器。
其中 Action 的名字是通过属性文件的
文件名 来获得的、 Action 中待转换的属性名是通过属性文件中的key 来获得的，该属性对应的类型转换器是通过该key 对应的value 来获得的。文章源自浅海拾贝-https://blog.terwergreen.com/struts2-type-conversion-single-object-in-depth-research-z2gmzxt.html
StrutsTypeConverter
Base class for type converters used in Struts. This class provides two abstract methods that are used to convert both to and from strings -- the critical functionality that is core to Struts's type coversion system.文章源自浅海拾贝-https://blog.terwergreen.com/struts2-type-conversion-single-object-in-depth-research-z2gmzxt.html
Type converters do not have to use this class. It is merely a helper base class, although it is recommended that you use this class as it provides the common type conversion contract required for all web-based type conversion.文章源自浅海拾贝-https://blog.terwergreen.com/struts2-type-conversion-single-object-in-depth-research-z2gmzxt.html
There's a hook (fall back method) called performFallbackConversion** of which could be used to perform some fallback conversion if** convertValue method of this failed. By default it just ask its super class (Ognl's DefaultTypeConverter) to do the conversion.文章源自浅海拾贝-https://blog.terwergreen.com/struts2-type-conversion-single-object-in-depth-research-z2gmzxt.html
To allow the framework to recognize that a conversion error has occurred, throw an XWorkException or preferable a TypeConversionException.文章源自浅海拾贝-https://blog.terwergreen.com/struts2-type-conversion-single-object-in-depth-research-z2gmzxt.html
使用 StrutsTypeConverter 进行类型转换实例
新建一个 test.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Struts2.3 converter</title>
</head>
<body>
<form action="userAction.action">
user info: <input type="text" name="user"/><br/>
<input type="submit" value="submit"/>
</form>
</body>
</html>
流程处理 Struts.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
"http://struts.apache.org/dtds/struts-2.3.dtd">
<struts>
<package name="struts2" extends="struts-default">
<action name="userAction" class="space.terwer.struts23.UserAction">
<result name="success">/output.jsp</result>
</action>
</package>
</struts>
Action 处理类 UserAction
package space.terwer.struts23;
import com.opensymphony.xwork2.ActionSupport;
import space.terwer.bean.User;
public class UserAction extends ActionSupport {
private User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
@Override
public String execute() throws Exception {
System.out.println("username:" + this.getUser().getUsername());
System.out.println("password:" + this.getUser().getPassword());
return SUCCESS;
}
}
类型转换器 UserConverter2.java
package space.terwer.converter;
import java.util.Map;
import org.apache.struts2.util.StrutsTypeConverter;
import space.terwer.bean.User;
public class UserConverter2 extends StrutsTypeConverter {
@Override
public Object convertFromString(Map context, String[] values, Class toClass) {
String firstValue = values[0];
String[] st = firstValue.split(";");
String uername = st[0];
String password = st[1];
User user = new User();
user.setUsername(uername);
user.setPassword(password);
return user;
}
@Override
public String convertToString(Map context, Object o) {
User user = (User) o;
String username = user.getUsername();
String password = user.getPassword();
String userInfo = "Use StrutsTypeConverter converted from UserConverter2=>username: " + username
+ ", password: " + password;
return userInfo;
}
}
类型转换配置 UserAction-conversion.properties
user=space.terwer.converter.UserConverter2
结果展示 output.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Struts2.3 converter result</title>
</head>
<body>
<s:property value="user"/>
</body>
</html>
实际效果
文章源自浅海拾贝-https://blog.terwergreen.com/struts2-type-conversion-single-object-in-depth-research-z2gmzxt.html
总结
可以使用 Struts2 框架自带的类型转换器 StrutsTypeConverter 简化类型转换代码的编写，StrutsTypeConverter 类继承于 DefaultTypeConverter 父类，并且提供了两个抽象方法： convertFromString 和 convertToString ，分别表示 从页面额字符串转换为后台对象 以及 从后台对象转换为页面字符串 ，我们 只需要实现这两个抽象方法即可实现类型转换 。文章源自浅海拾贝-https://blog.terwergreen.com/struts2-type-conversion-single-object-in-depth-research-z2gmzxt.html
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