Struts2类型转换之单个对象深入研究

Terwer Struts2评论26字数 3460阅读11分32秒阅读模式

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。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

Struts2类型转换之单个对象深入研究文章源自浅海拾贝-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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