json学习系列（2）-生成JSONObject的方法

生成JSONObject一般有两种方式，通过javabean或者map类型来生成。如下面的例子：

先定义一个User实体类:

package com.pcitc.json;

/**
 * 用户实体类
 *
 * @Description
 * @author admin
 * @created 2015年6月29日 下午3:43:15
 * @version
 * @history
 * @see
 */
public class User {
    public String username;
    public String password;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

测试类如下:

package com.pcitc.json;

import java.util.HashMap;
import net.sf.json.JSONObject;

/**
 * 测试类
 *
 * @Description
 * @author admin
 * @created 2015年6月29日 下午3:57:01
 * @version
 * @history
 * @see
 */
public class Test {

    public static void main(String args[]) {

        User user = new User();
        user.setUsername("root");
        user.setPassword("1234");
        // 通过javabean来生成JSONObject对象
        JSONObject json1 = JSONObject.fromObject(user);
        System.out.println("javabean方式:\r\n" + json1.toString());
        HashMap<Object, Object> userMap = new HashMap<Object, Object>();
        userMap.put("username", "root");
        userMap.put("password", "1234");
        // 通过map类型来生成JSONObject
        JSONObject json2 = JSONObject.fromObject(userMap);
        System.out.println("map方式:\r\n" + json2.toString());

    }
}

测试结果如下所示：

aaarticlea/png;base64,iVBORw0KGgoAAAANSUhEUgAAAbAAAABvCAIAAAACMwIzAAAKaUlEQVR4nO2d28GrKhBGbWtbEO38lnCqsBmL8TyEGC4zA3iNZq23iJDh9smAQjfDWYyu67quc+Pp/zz9/RP/Vrt+Gb6I/v1Nm9LYmKfp79+Swug2mnM227Nvpfz39+8LisM3k4VVGZYLqttuHXw9txHEb2H6+/fubNd3/y/huuf5mSCIAAAeWRD/AwD4PRghAgB4EEQAAA+CCADgQRABADwIIgCAp14QR9d1XT8c91LW6B7/khMAfDW/Lohd1zBGft3cFAUAbsQX9e2rRoj1ArfciSYCPJIv6tinCWJXwoh4gnkAcBWFHp5+RZ24zGHwEjQNfaJso4tiirHegjgNvfzJdhgr0U09wX6YgsBUbm3tqxfNl83MfwLcnYYhTyJr8zT0Hw0YXSAJ8Z2xQNqxPj+jWFkSKxJMzZ/bR3za/QgiwDPYIIh5aLRn0vvWaej1aGGs1GX+/M6S0L1rI8E8UpO/POMyAzydLYIYeLepS/qRsEzM1FiSIL5ipo57/Ge1CYqCmBZHcCUXSgQR4NmsFsRp6IUZwPhuN6aXrVj6CNFYbmlIsFUQ8ysIIsCz2SaIkY8srKQ454ThoRIrFqzo3/J1mvYE05+iuhUlUozFHCLAM9i2qLL4k/0wDn0iCa/wdPpQj5W4vom+pI6x6DHHCR4niB2rzABPpFEQn9LpNedXFMRwGnG5cqx9AHAFdscenfKuy60xVM+4YqcAAA+g1LGN15oBAJ4FIx0AAA+CCADgQRABADwIIgCAB0EEAPDUCuL79efwPetlD+0nv5icfz/TnuUvKahbG38mty4owwz/ysiR297fnjpBlDe6+ey1Fe269SwEQWzOciGWf9hkiQWvPFnbY+ifNAofU+5u/BO5Q0Gpn0mUzHjQC8VHUCWIyg5en6J9cFeJG966LBuxXo+aIU9sSj9qVJ7r4rNqGvqu79OGv7vxT+UOBaUKYtEMcz++n2cfQXxwGWuC2JJlNdbo6nqQ9VTPe4b/kyxgZ+Ofyx0KqkIQjW77E9W4ii2CqFLYu1/Z8X9OncG8N6dBomFhU4liJfOf/TAFpuTOZcEplVg7e7ReEPMSWO49+ttze+8MoyrV0yD0SlnToqah79zwMuMTObG4uYrnFbVsNja1iSpB2fafebyy+QiiRpUgtnYt4zAAY8d/62+0IOH6p77j1GO/M55fDk1MxKcp7wcJYu4yB71COObmldKVgqj/t3UahF4p1mkQWotadlv6bLsUb8KumVFijSBa+ZKbqNV65021K68IwDzPlYdMtRa8vtWreachC1rQMtMWy6AbpUYePhqTRpFHL9u+I6YgLsuGIrnOv9O5WhDFPzdPg1ArpbzXrxC0RI9n1WRv8tDC0vJlNFG79W43+HdeGWikZoTYvC4liUq82WuI4j8YGylmJ+vN09A75/phWq5InkFgl9aesrxeLIgVTyRNzK91mfX6yilLuPlfSouyBNE0Y3esxqY0Ubv1GmlWgM9scNQcoiIq6cjfnhqW/zMKeg0RX17T6Lx/tAwC7BGiqkDfIoh1j3G7l1ujy+1G14zaMkdQzdAaQdRbVEkQzxseVT99TxkhoocWJwhiOD6U5oz0uSblP6Og0XW9c/27mYeHFgizMBWTXIG576HHJXOIlWnpE0LrZn7r61mf4xNurDgNYoMgii3KEsR2ryfJT/McYs1UUGSU1XqlC03mI4gahwmi5oqE/o15hIB2WoEYFPXLpOeIdlhq8YkUjjhraO0qwophosVSQcbFu2K8ZURoGk8GhrhxqqtKIW+VTyltNKq1KFMQLTNK7CiIs9FEzaAs36wy78MpLjPcA3v5Bp4Bgmix5dM983YE8W6w8PgTbJks+AG2bO6ggiDejWZvGW5I/D4kSLD9FwCAB0EEAPAgiAAAHgQRAMCDIAIAeBBEAADPZYLYdQ1//bq5KQoAQCtXSky9wC13ookAcByn6kv+dW6CEfFMOwHgNzGFpmkT9myTwujT/+RfTe2rF02+NgOAHSkKoroJu3EYQKycwseTrSM+7X4EEQB2pCiI1gZKIdbm9VmkJn95xmUGgFPYIojqYQDmEQLzLAlceCUXSgQRAE5gtSBahwHUjBBTO0oSWZ8lAIB1bBNE5TAA/QiBeVbUrSiRYizmEAFgRza4zPphANYRAtsEkVVmADiOQ1xRY4NYzfkVBTFZbymuvQAAbOFUQTRUz7hipwAAsBdnjxABAL4WBlwAAB4EEQDAgyACAHgQRAAAD4IIAODZclD96PyF33k/el2Wv6Sgbm38seTfVt22oAwzOKi+TJ0gZrszLFc/3688tKvErMvyuQVlbkj07cZfhCCIexeUH1JkiQWfdUVdLNk6RTRCSrNkvLAbH3yoEsTlE7788uO7Ssy6LJ9bUKog3sH4i4jLbPeCeg0ohjyxKfjgNd0uJbUvC5qGvuv7VN6Kxiu9GeZ53ksQf6aM12X53IKqEMTvNf4iNEHcpaBGV6eu1tgtr1T/J1lA0fgHV+MObBFElaSSkp+xLxDXcrgtRPKIfe/XnQQWjisQDzloOhqhZUjUPHuk52tOCioufzEo258yj7cna0pesDPvzWmQ2PzUjTmTWW69eAt7kOisnSNcL4h5CSz3tn8VhiBaVAlia6FbgqinFbcHaXuxdz2GYbGaxa6FdsiBeTSCZUaJNYJo5Ss2450xI+gdfIZjax0UoR8vYZmnBQnXP73aKg29eJN6bSqzgwQxd5kDoU8U7GPvitqWVwRgnueiIMb7HNZSEkQxwezBlW45GwQG99qjUdmq0j6Pqhm7o+Ur1+GaoBMMTmxPJ8rk/61rAHrQMtMWy6AbS6WhNpt623fEFMRlcVgk1/mwZ6yw/MmvDGyiZoTYvC5VECn5wZc4MLEbU9nZxMmgPD1LEE0zdkfLl+DWhBKgjhesNPdGEpVoVkItQn3ko7cN/yKJc64fpuVKoTSs4v0mQawYd2hivsJyfGaDC+YQ43Sjp7las2sEUT/koCSI5z04q3vsrUaIesknGAurUdBriPjyw0fn5zqWMaM9QlQV6FsEsW6wZj+xrdGl9H/oocYhgqjP8VkJty2yKSGpICazkGVB3PSe1qo5xBr3MTLKCBIvNNjSMrmUj1Si1R2x5FOMlhUFja7rnevfVeWcs2ZUK+YrA3Pfg9JL5hAr09Kn/VhU2ZdDBDF6jLlxeZzPmSuVpJo6WpUtWxuNhsmFhxyYgmiZUWJHQZyTsUB8lxGU5bu63hoV0Vqk1UrebADFoOgZm1S6aIdVvJ9I4YizhtZaFlb/Ey2WCjIu3hW+k2UOgqhxkCDCHbEn9qW7mZW/H/Rmiy2f7sGjaB34IIi3ZMuU0A+wZXMHeAyt84fvOHSsOxG/lgkSbP8FAOBBEAEAPAgiAIAHQQQA8CCIAAAeBBEAwIMgAgB4EEQAAA+CCADgQRABADwIIgCAB0EEAPAgiAAAHgQRAMCDIAIAeBBEAAAPgggA4EEQAQA8CCIAgAdBBADwIIgAAB4EEQDAgyACAHgQRAAAD4IIAOBBEAEAPAgiAIAHQQQA8CCIAAAeBBEAwIMgAgB4/gewSThqU5T21AAAAABJRU5ErkJggg==" alt="" />

接下来从源码层次分析一下JSONObject.fromObject()方法：

public static JSONObject fromObject(Object object)
{
    return fromObject(object, new JsonConfig());
}

此函数可以接受的参数类型为：JSON formatted strings，Maps，DynaBeans and JavaBeans。
【注意】DynaBeans是commons-beanutils定义的动态bean。DynaBean并不是Java中所定义的Bean，而是一种"假"的Bean。因为它并不是通过getXXX和setXXX方法，对XXX属性进行取值和设值的。
如果object是其他类型的参数呢？比如说数字，逻辑值，非json格式的字符串，那么将生产空的JSONObject对象。

if (JSONUtils.isNumber(object) || JSONUtils.isBoolean(object) || JSONUtils.isString(object))
{
    return new JSONObject();
}

JSONObject的构造函数有两个：

public JSONObject()
{
        this.properties = new ListOrderedMap();
}
public JSONObject(boolean isNull)
{
        this();
        this.nullObject = isNull;
}

不过，通常都是使用第一个无参的构造函数，第二个构造函数使用情况很少。