Java：JSON解析工具-org.json

一、简介 

org.json是Java常用的Json解析工具，主要提供JSONObject和JSONArray类，现在就各个类的使用解释如下。 

二、准备 

1.在使用org.json之前，我们应该先从该网址https://github.com/douglascrockford/JSON-java下载org.json源码，并将源码其加入到Eclipse中，即可调用。 

2.查看相关的API文档，访问：https://github.com/douglascrockford/JSON-java。 

https://github.com/stleary/JSON-Java-unit-test

三、讲解： 

1.JSONObject： 

• 是一个无序的键/值对集合。 

• 它的表现形式是一个包裹在花括号的字符串，键和值之间使用冒号隔开，键值和键值之间使用逗号隔开。 

• 内在形式是一个使用get()和opt()方法通过键来访问值，和使用put()方法通过键来添加或者替代值的对象。 

• 值可以是任何这些类型：Boolean,JSONArray,JSONObject,Number和String，或者JOSONObject.NULL对象。 

代码演示如下： 

 

public static void jsonObjectTest() {
ﾠ ﾠ JSONObject jsonobj = new JSONObject("{'name':'xiazdong','age':20}");
    String name = jsonobj.getString("name");
ﾠ ﾠ int age = jsonobj.getInt("age");
    System.out.println("name = " + name + ",age = " + age);
}

注：JSONObject有很多optXXX方法，比如optBoolean, optString, optInt... 

他们的意思是，如果这个jsonObject有这个属性，则返回这个属性，否则返回一个默认值。 

2.JSONArray： 

• 是一个有序的序列值。 

• 它的表现形式是一个包裹在方括号的字符串，值和值之间使用逗号隔开。 

• 内在形式是一个使用get()和opt()方法通过索引来访问值，和使用put()方法来添加或修改值的对象。 

• 值可以是任何这些类型：Boolean,JSONArray,JSONObject,Number,和String，或者JSONObject.NULL对象。 

代码演示如下： 

 

public static void jsonArrayTest() {
ﾠ ﾠ JSONArray jsonarray = new JSONArray("[{'name':'xiazdong','age':20},{'name':'xzdong','age':15}]");
ﾠ ﾠ for (int i = 0; i < jsonarray.length(); i++) {
ﾠ ﾠ ﾠ ﾠﾠJSONObject jsonobj = jsonarray.getJSONObject(i);
        String name = jsonobj.getString("name");
        int age = jsonobj.getInt("age");
        System.out.println("name = " + name + ",age = " + age);
    }
}

嵌套的JSONObject和JSONArray代码演示如下： 

 

public static void jsonObjectAndArrayTest() {
ﾠ ﾠ String jsonstring = "{'name':'xiazdong','age':20,'book':['book1','book2']}";
ﾠ ﾠ JSONObject jsonobj = new JSONObject(jsonstring);

    String name = jsonobj.getString("name");
ﾠ ﾠ System.out.println("name" + ":" + name);

    int age = jsonobj.getInt("age");
    System.out.println("age" + ":" + age);

ﾠ ﾠ JSONArray jsonarray = jsonobj.getJSONArray("book");
ﾠ ﾠ for (int i = 0; i < jsonarray.length(); i++) {
        String book = jsonarray.getString(i);
ﾠ ﾠ ﾠ ﾠ System.out.println("book" + i + ":" + book);
    }
}

3.JSONStringer： 

• 是一个用于快速构造JSON文本的工具 

• JSONWriter的子类 

• bject():开始一个对象，即添加{；enObject():结束一个对象，即添加} 

•  array():开始一个数组，即添加[； endArray():结束一个数组，即添加] 

• key():表示添加一个key；value():表示添加一个value 

代码演示如下： 

 

public static void jsonStringerTest() {
ﾠ ﾠ JSONStringer stringer = new JSONStringer();
    stringer.object().key("name").value("xiazdong").key("age").value(20).endObject();
ﾠ ﾠ System.out.println(stringer);
}

负载的JSON格式写演示（PrintWriter+JSONStringer可以写入JSON文件）： 

 

public static void jsonStringerTest2() throws FileNotFoundException {
ﾠ ﾠ JSONStringer jsonStringer = new JSONStringer();
ﾠ ﾠ JSONObject obj6 = new JSONObject();
    obj6.put("title", "book1").put("price", "$11");
ﾠ ﾠ JSONObject obj3 = new JSONObject();
    obj3.put("book", obj6);
ﾠ ﾠ obj3.put("author", new JSONObject().put("name", "author-1"));

ﾠ ﾠ JSONObject obj5 = new JSONObject();
    obj5.put("title", "book2").put("price", "$22");
ﾠ ﾠ JSONObject obj4 = new JSONObject();
    obj4.put("book", obj5);
 ﾠ ﾠobj4.put("author", new JSONObject().put("name", "author-2"));

ﾠ ﾠ JSONArray obj2 = new JSONArray();
    obj2.put(obj3).put(obj4);

ﾠ ﾠ JSONObject obj1 = new JSONObject();
    obj1.put("title", "BOOK");
    obj1.put("signing", obj2);

    jsonStringer.object().key("session").value(obj1).endObject();
    System.out.println(jsonStringer.toString());

ﾠ ﾠ PrintWriter out = new PrintWriter(new FileOutputStream("1.txt"));
ﾠ ﾠ out.println(jsonStringer.toString());
    out.close();
}

4.JSONTokener 

• 它和JSONObject和JSONArray的构造函数一起使用，用于解析JSON源字符串 

代码演示如下（JSONObject+JSONTokener能够获取JSON格式文本对象）： 

 

public static void JSONTokenerTest() throws FileNotFoundException {
    JSONObject jsonobj = new JSONObject(new JSONTokener(new FileReader(new File("1.txt"))));
    System.out.println(jsonobj.getJSONObject("session").getJSONArray("signing").getJSONObject(1).getJSONObject("book").getString("title"));
}

注意：在Java中，JSON格式的字符串最好用单引号表示 

JSON in Java [package org.json]

JSON is a light-weight, language independent, data interchange format.
See http://www.JSON.org/

The files in this package implement JSON encoders/decoders in Java.
It also includes the capability to convert between JSON and XML, HTTP
headers, Cookies, and CDL.

This is a reference implementation. There is a large number of JSON packages
in Java. Perhaps someday the Java community will standardize on one. Until
then, choose carefully.

The license includes this restriction: "The software shall be used for good,
not evil." If your conscience cannot live with that, then choose a different
package.

The package compiles on Java 1.6-1.8.


JSONObject.java: The JSONObject can parse text from a String or a JSONTokener
to produce a map-like object. The object provides methods for manipulating its
contents, and for producing a JSON compliant object serialization.

JSONArray.java: The JSONObject can parse text from a String or a JSONTokener
to produce a vector-like object. The object provides methods for manipulating
its contents, and for producing a JSON compliant array serialization.

JSONTokener.java: The JSONTokener breaks a text into a sequence of individual
tokens. It can be constructed from a String, Reader, or InputStream.

JSONException.java: The JSONException is the standard exception type thrown
by this package.

JSONPointer.java: Implementation of 
[JSON Pointer (RFC 6901)](https://tools.ietf.org/html/rfc6901). Supports
JSON Pointers both in the form of string representation and URI fragment
representation.

JSONString.java: The JSONString interface requires a toJSONString method,
allowing an object to provide its own serialization.

JSONStringer.java: The JSONStringer provides a convenient facility for
building JSON strings.

JSONWriter.java: The JSONWriter provides a convenient facility for building
JSON text through a writer.


CDL.java: CDL provides support for converting between JSON and comma
delimited lists.

Cookie.java: Cookie provides support for converting between JSON and cookies.

CookieList.java: CookieList provides support for converting between JSON and
cookie lists.

HTTP.java: HTTP provides support for converting between JSON and HTTP headers.

HTTPTokener.java: HTTPTokener extends JSONTokener for parsing HTTP headers.

XML.java: XML provides support for converting between JSON and XML.

JSONML.java: JSONML provides support for converting between JSONML and XML.

XMLTokener.java: XMLTokener extends JSONTokener for parsing XML text.

Unit tests are maintained in a separate project. Contributing developers can test 
JSON-java pull requests with the code in this project: 
https://github.com/stleary/JSON-Java-unit-test

package com.json;

import java.text.ParseException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

/**
 * 使用json-lib构造和解析Json数据
 * 
 * @author Alexia
 * @date 2013/5/23
 * 
 */
public class OrgJsonTest {

    /**
     * 构造Json数据
     * 
     * @return
     * @throws JSONException
     */
    public static String BuildJson() throws JSONException {

        // JSON格式数据解析对象
        JSONObject jo = new JSONObject();

        // 下面构造两个map、一个list和一个Employee对象
        Map<String, String> map1 = new HashMap<String, String>();
        map1.put("name", "Alexia");
        map1.put("sex", "female");
        map1.put("age", "23");

        Map<String, String> map2 = new HashMap<String, String>();
        map2.put("name", "Edward");
        map2.put("sex", "male");
        map2.put("age", "24");

        List<Map> list = new ArrayList<Map>();
        list.add(map1);
        list.add(map2);

        Employee employee = new Employee();
        employee.setName("wjl");
        employee.setSex("female");
        employee.setAge(24);

        // 将Map转换为JSONArray数据
        JSONArray ja = new JSONArray();
        ja.put(map1);

        System.out.println("JSONArray对象数据格式：");
        System.out.println(ja.toString());

        // 将Javabean转换为Json数据（需要Map中转）
        JSONObject jo1 = JsonHelper.toJSON(employee);

        System.out.println("
仅含Employee对象的Json数据格式：");
        System.out.println(jo1.toString());

        // 构造Json数据，包括一个map和一个含Employee对象的Json数据
        jo.put("map", ja);
        jo.put("employee", jo1.toString());
        System.out.println("
最终构造的JSON数据格式：");
        System.out.println(jo.toString());

        return jo.toString();

    }

    /**
     * 解析Json数据
     * 
     * @param jsonString
     *            Json数据字符串
     * @throws JSONException
     * @throws ParseException
     */
    public static void ParseJson(String jsonString) throws JSONException,
            ParseException {

        JSONObject jo = new JSONObject(jsonString);
        JSONArray ja = jo.getJSONArray("map");

        System.out.println("
将Json数据解析为Map：");
        System.out.println("name: " + ja.getJSONObject(0).getString("name")
                + " sex: " + ja.getJSONObject(0).getString("sex") + " age: "
                + ja.getJSONObject(0).getInt("age"));

        String jsonStr = jo.getString("employee");
        Employee emp = new Employee();
        JsonHelper.toJavaBean(emp, jsonStr);

        System.out.println("
将Json数据解析为Employee对象：");
        System.out.println("name: " + emp.getName() + " sex: " + emp.getSex()
                + " age: " + emp.getAge());

    }

    /**
     * @param args
     * @throws JSONException
     * @throws ParseException
     */
    public static void main(String[] args) throws JSONException, ParseException {
        // TODO Auto-generated method stub

        ParseJson(BuildJson());
    }

}

运行结果如下

五、与json-lib比较

      json-lib和org.json的使用几乎是相同的，我总结出的区别有两点：

      1. org.json比json-lib要轻量得多，前者没有依赖任何其他jar包，而后者要依赖ezmorph和commons的lang、logging、beanutils、collections等组件

      2. json-lib在构造bean和解析bean时比org.json要方便的多，json-lib可直接与bean互相转换，而org.json不能直接与bean相互转换而需要map作为中转，若将bean转为json数据，首先需要先将bean转换为map再将map转为json，比较麻烦。

      总之，还是那句话—适合自己的才是最好的，大家要按需选取使用哪种方法进行解析。最后给大家介绍两款解析Json数据的工具：一是在线工具JSON Edit（http://braincast.nl/samples/jsoneditor/）；另一个是Eclipse的插件JSON Tree Analyzer，都很好用，推荐给大家使用！

http://www.cnblogs.com/lanxuezaipiao/archive/2013/05/24/3096437.html