使用Struts 2將Java對象序列化成JSON

Struts 2有個很強大的功能，就是可以自動完成服務器端Java對象和客戶端JSON對象之間的映射。這篇文章就介紹一下如何將Java對象序列化成JSON格式並傳到客戶端。可以看看不同的Java類型和JSON類型之間是如何映射的。

 

pom.xml

需要引入struts2-json-plugin包。

<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”；負責映射的TestAction設置result type爲json。

<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

<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", /*設置返回數據的類型，和服務器端的設置一致*/
                sync : true
            };
            var deferred = xhr.get(xhrArgs);

            deferred.then(function(result) {
                var output = JSON.stringify(result); /*將返回值變成json string*/
                console.log(output); /*打印到Firebug console*/
            });
        });
    });
</script>

TestAction.java

TestAction中，凡是有setter方法的屬性都會被轉換成JSON並輸出到客戶端。

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

{"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]

總結

可以看到，從JAVA對象轉換到JSON格式還是非常直白的。由於JAVA對象比較複雜，表達能力強，而JSON格式比較簡單，表達能力弱，因此這種轉換大致不太會出錯。而相反的，如果要將JSON轉換成JAVA，則需要考慮是否需要額外的信息幫助將簡單的格式轉換成複雜對象。可以想象這中間會出現歧義。

參考文獻

[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