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Struts2类型转换之单个对象深入研究

重要特性总结

  1. 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。

  2. 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。

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.

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.

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.

To allow the framework to recognize that a conversion error has occurred, throw an XWorkException or preferable a TypeConversionException.

使用 StrutsTypeConverter 进行类型转换实例

新建一个 test.jsp

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<%@ 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

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<?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

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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

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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

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user=space.terwer.converter.UserConverter2

结果展示 output.jsp

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<%@ 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

​

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 。

Struts2类型转换之单个对象深入研究

https://hexo.terwer.space/post/struts2-type-conversion-single-object-in-depth-research-z2gmzxt.html

作者

Terwer

发布于

2022-10-30

更新于

2022-10-30

许可协议

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