[原]Struts2类型转换

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Struts Java JavaEE Apache XML

[标题]:[原]Struts2类型转换
[时间]:2009-7-15
[摘要]:Struts2类型转换、全局类型转换、集合类型转换
[关键字]:浪曦视频，Struts2应用开发系列，WebWork，Apache，类型转换
[环境]:struts-2.1.6、JDK6、MyEclipse7、Tomcat6
[作者]:Winty (wintys@gmail.com) http://www.blogjava.net/wintys

[正文]:
   在Struts Action中可以自动转换String，Date等类型，但是如果Action中用到自定义类型，就需要使用Struts类型转换。

1、Struts类型转换
自定义类型Point
public class Point {
   private int x;
   private int y;

   //省略getter and setter
}

Struts Action：
public class PointAction extends ActionSupport {
   private Point point;
   ......
}

客户端输入:
<s:textfield name="point" label="坐标" ></s:textfield>

   这样，从客户端传过来point的String值，不能直接set到PointAction中的point对象中。同时，输出point对象时，直接调用getter也是不行的。这时，就需要一个类型转换器，实现Point类与String之间的转换。可以继承Struts中的ognl.DefaultTypeConverter实现。

/StrutsHelloWorld/src/wintys/struts2/converter/PointConverter.java:

package wintys.struts2.converter;

import java.util.Map;

import ognl.DefaultTypeConverter;

public class PointConverter extends DefaultTypeConverter {

   @SuppressWarnings("unchecked")
   @Override
   public Object convertValue(Map context, Object value, Class toType) {
       //String => Point
       if(toType == Point.class){
           //获取request string的字符串数组
           String[] params = (String[])value;
           String param = params[0];
           String[] points = param.split(",");

           Point point = new Point();
           point.setX(Integer.parseInt(points[0]));
           point.setY(Integer.parseInt(points[1]));

           return point;
       }

       //Point => String
       if(toType == String.class){
           Point point = (Point)value;
           int x = point.getX();
           int y = point.getY();

           return "["+x+","+y+"]";
       }

       return null;
   }

}

   同时，还需要一个配置文件(须跟PointAction在同一目录下)PointAction-conversion.properties(名称为XXXAction-conversion.properties)来告诉Struts2 PointAction中属性使用哪一个转换器类。

PointAction-conversion.properties:
point=wintys.struts2.converter.PointConverter

2、Struts全局类型转换
   对于每一个属性应用转换器，当属性过多时会显得很繁琐，这时可以使用Struts全局类型转换。全局类型转换器名称为xwork-conversion.properties，与struts.xml同在classes目录下。

xwork-conversion.properties:
#global converter settings
#class to be converted = converter
wintys.struts2.converter.Point=wintys.struts2.converter.PointConverter

3、Struts集合类型转换
   当PointAction中的属性是集合类型，跟非集合类型类似。
   public class PointAction extends ActionSupport {
       private List<Point> points;
       ......
   }

   转换器类可以继承org.apache.struts2.util.StrutsTypeConverter，实际上StrutsTypeConverter继承于 ognl.DefaultTypeConverter。

/StrutsHelloWorld/src/wintys/struts2/converter/StrutsPointConverter.java:

package wintys.struts2.converter;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.apache.struts2.util.StrutsTypeConverter;

/**
* Struts类型转换: StrutsTypeConverter 继承于 ognl.DefaultTypeConverter
* @author Winty
* @version 2009-07-14
*
*/
@SuppressWarnings("unchecked")
public class StrutsPointConverter extends StrutsTypeConverter {

   @Override
   public Object convertFromString(Map context, String[] values, Class toClass) {
       List<Point> points = new ArrayList<Point>();
       for(String value : values){
           String[] p = value.split(",");
           Point point = new Point();
           point.setX(Integer.valueOf(p[0]));
           point.setY(Integer.valueOf(p[1]));

           points.add(point);
       }
       return points;
   }

   @Override
   public String convertToString(Map context, Object o) {
       List<Point> points = (List<Point>)o;
       StringBuilder sb = new StringBuilder();
       sb.append("[");
       for(Point p : points){
           sb.append("(");
           sb.append(p.getX());
           sb.append(",");
           sb.append(p.getY());
           sb.append(") ");
       }
       sb.append("]");

       return sb.toString();
   }

}

当然也需要在PointAction-conversion-properties中配置:
PointAction-conversion-properties:

#property = converter
point=wintys.struts2.converter.PointConverter
points=wintys.struts2.converter.StrutsPointConverter

4、详细内容:
/StrutsHelloWorld/WebRoot/converter/input.jsp:
其中<s:textfield name="point" label="坐标" ></s:textfield>
可以换成
<s:textfield name="point.x" label="坐标.x"/>
<s:textfield name="point.y" label="坐标.y"/>
此时，Point类无需类型转换，Struts会自己去找point对象的x与y的setter方法。
当输出时，只需重写Point类的toString()方法即可。

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%@ taglib uri="/struts-tags" prefix="s" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
</head>

<body>
   <h1>请以逗号分割输入点的坐标，如:5,3</h1>
   <s:form action="pointConverter">
       <s:textfield name="point" label="坐标" ></s:textfield>
       <s:textfield name="points" label="points1"> </s:textfield>
       <s:textfield name="points" label="points2"></s:textfield>
       <s:textfield name="age" label="年龄"></s:textfield>
       <s:textfield name="name" label="姓名"></s:textfield>
       <s:textfield name="birthday" label="出生日期"></s:textfield>
       <s:submit value="确定"></s:submit>
   </s:form>
</body>
</html>

/StrutsHelloWorld/WebRoot/converter/output.jsp:

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%@ taglib uri="/struts-tags" prefix="s"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
</head>

<body>
   <s:property value="point"/><br/>
   <s:property value="points"/><br/>
   <s:property value="age"/><br/>
   <s:property value="name"/><br/>
   <s:property value="birthday"/> <br/>
</body>
</html>

/StrutsHelloWorld/src/struts.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">

<struts>
    <package name="MyStruts" extends="struts-default">
        <action name="pointConverter" class="wintys.struts2.converter.PointAction">
           <result name="success">/converter/output.jsp</result>
        </action>
    </package>
</struts>

/StrutsHelloWorld/WebRoot/WEB-INF/web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
   xmlns="http://java.sun.com/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
   http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
   <filter>
       <filter-name>MyStruts2</filter-name>
       <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>
   </filter>

   <filter-mapping>
       <filter-name>MyStruts2</filter-name>
       <url-pattern>/*</url-pattern>
   </filter-mapping>
</web-app>

/StrutsHelloWorld/src/wintys/struts2/converter/Point.java:

package wintys.struts2.converter;

/**
*
* @author Winty
* @version 2009-07-12
*/
public class Point {
   private int x;
   private int y;

   public int getX() {
       return x;
   }
   public void setX(int x) {
       this.x = x;
   }
   public int getY() {
       return y;
   }
   public void setY(int y) {
       this.y = y;
   }
}

/StrutsHelloWorld/src/wintys/struts2/converter/PointAction.java:

package wintys.struts2.converter;

import java.util.Date;
import java.util.List;

import com.opensymphony.xwork2.ActionSupport;

/**
*
* @author Winty
* @verion 2009-07-12
*/
@SuppressWarnings("serial")
public class PointAction extends ActionSupport {
   private Point point;
   private List<Point> points;//集合类型的转换
   private int age;
   private String name;
   private Date birthday;

   public Point getPoint() {
       return point;
   }
   public void setPoint(Point point) {
       this.point = point;
   }
   public int getAge() {
       return age;
   }
   public void setAge(int age) {
       this.age = age;
   }
   public String getName() {
       return name;
   }
   public void setName(String name) {
       this.name = name;
   }
   public Date getBirthday() {
       return birthday;
   }
   public void setBirthday(Date birthday) {
       this.birthday = birthday;
   }
   public List<Point> getPoints() {
       return points;
   }
   public void setPoints(List<Point> points) {
       this.points = points;
   }

   @Override
   public String execute() throws Exception {
       return SUCCESS;
   }
}

[参考资料]:
《浪曦视频之Struts2应用开发系列》

[附件]:
源代码: StrutsTypeConverter.zip