使用Struts 2将Java对象序列化成JSON

Struts 2有个很强大的功能，就是可以自动完成服务器端Java对象和客户端JSON对象之间的映射。这篇文章就介绍一下如何将Java对象序列化成JSON格式并传到客户端。可以看看不同的Java类型和JSON类型之间是如何映射的。



pom.xml

需要引入struts2-json-plugin包。

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<dependencies>

<dependency>

<groupId>org.apache.struts</groupId>

<artifactId>struts2-core</artifactId>

<version>2.3.12</version>

</dependency>

<dependency>

<groupId>org.apache.struts</groupId>

<artifactId>struts2-json-plugin</artifactId>

<version>2.3.12</version>

</dependency>

</dependencies>

struts.xml

package extends要增加”json-default”；负责映射的TestAction设置result type为json。

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<package name="sandbox" namespace="/" extends=" struts-default, json-default">

<action name="main" class="sandbox.z.MainAction">

<result>/jsp/main.jsp</result>

</action>

<action name="test" class="sandbox.z.TestAction">

<result type="json" />

</action>

</package>

main.jsp

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<script>

require([ "dojo/ready",

"dojo/_base/xhr",

"dojo/json",

"dijit/registry" ], function(ready, xhr, JSON, registry) {

ready(function() {

var xhrArgs = {

url : "/test.action",

handleAs : "json", /*设置返回数据的类型，和服务器端的设置一致*/

sync : true

};

var deferred = xhr.get(xhrArgs);



deferred.then(function(result) {

var output = JSON.stringify(result); /*将返回值变成json string*/

console.log(output); /*打印到Firebug console*/

});

});

});

</script>

TestAction.java

TestAction中，凡是有setter方法的属性都会被转换成JSON并输出到客户端。

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package sandbox.z;



import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;



import com.opensymphony.xwork2.ActionSupport;



public class TestAction extends ActionSupport {



private static final long serialVersionUID = 1L;



private String name = "john";

private int age = 30;

private double height = 1.78;

private int[] scores = {85, 90};



private List<Integer> score_array = new ArrayList<Integer>();



public void setScore_array(List<Integer> score_array) {

this.score_array = score_array;

}



public List<Integer> getScore_array() {

return score_array;

}



private List array = new ArrayList();



public List getArray() {

return array;

}



public void setArray(List array) {

this.array = array;

}



private Map books_map = new HashMap();



public void setBooks_map(Map books_map) {

this.books_map = books_map;

}



public Map getBooks_map() {

return books_map;

}



private Book book = new Book();



public void setBook(Book book) {

this.book = book;

}



public Book getBook() {

return book;

}



public String execute() {

score_array.add(85);

score_array.add(90);



array.add(85);

array.add("Struts2");



books_map.put("struts2", 85);



getBook().setName("Struts2");

getBook().setPrice(85.30);



List<String> sellers = new ArrayList<String>();

sellers.add("SA");

sellers.add("SB");

getBook().setSellers(sellers);



return SUCCESS;

}



public void setName(String name) {

this.name = name;

}



public String getName() {

return name;

}



public void setAge(int age) {

this.age = age;

}



public int getAge() {

return age;

}



public void setHeight(double height) {

this.height = height;

}



public double getHeight() {

return height;

}



public void setscores(int[] scores) {

this.scores = scores;

}



public int[] getscores() {

return scores;

}



}

Firebug console

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{"age":30,"array":[85,"Struts2"],"book":{"name":"Struts2","price":85.3,"sellers":["SA","SB"]},"books_map":{"struts2":85},"height":1.78,"name":"john","score_array":[85,90],"scores":[85,90]

总结

可以看到，从J***A对象转换到JSON格式还是非常直白的。由于J***A对象比较复杂，表达能力强，而JSON格式比较简单，表达能力弱，因此这种转换大致不太会出错。而相反的，如果要将JSON转换成J***A，则需要考虑是否需要额外的信息帮助将简单的格式转换成复杂对象。可以想象这中间会出现歧义。

参考文献

[1] JSON Plugin. http://struts.apache.org/release/2.2.x/docs/json-plugin.html
原文地址:http://blog.csdn.net/eengel/article/details/8809618