JSON — Java與JSON資料互轉

阿新 • • 發佈：2019-01-02

轉換時Bean所要求的：

被轉換的Bean必需是public的。
Bean被轉換的屬性一定要有對應的get方法，且一定要是public的。
Bean中不能用引用自身的this的屬性，否則執行時出現et.sf.json.JSONException: There is a cycle in the hierarchy!異常
json-lib包轉換時，不能以null為鍵名，否則執行報net.sf.json.JSONException:java.lang.NullPointerException:JSON keys must not be null nor the 'null' string.
json-lib包轉換時，

轉換成XML元素key的名字要符合XML元素標籤的命名規則，否則會報nu.xom.IllegalNameException: NCNames cannot start with the character 25異常

轉換時問題：

如果某個Bean中存在存放陣列的Map屬性，則使用org.json包中的JSONObject直接封裝時得不到正確的JSON，要用JSONArray對陣列進行封裝處理，否則為轉換JavaScript中的空的物件{}，但能使用json-lib包很好地解決這一問題

兩種包的比較：

json-lib包比org.json要易使用些，至少沒有煩人的JSONExcetipn捕獲異常了。
json-lib對Bean的支援比org.json要強，特別是對bean中內嵌屬性的支援較好。

commons-beanutils-1.8.0.jar
commons-collections-3.2.1.jar
commons-lang-2.4.jar
commons-logging-1.1.1.jar
ezmorph-1.0.6.jar
json-lib-2.3-jdk15.jar
xom-1.2.2.jar

例項所用到的三個Bean

Java程式碼

package bean;  
  
import java.util.ArrayList;  
import java.util.HashMap;  
import java.util.HashSet;  
import java.util.List;  
import java.util.Map;  
import java.util.Set;  
  
/** 
 * POJO 定義各種型別的屬性，便於測試 
 * (C) 2009-9-7, jzj 
 */  
public class OtherBean {  
    /* 
     * 定義一個整數屬性 
     */  
    private int intAttr = 1;  
  
    /* 
     * 定義一個浮點數屬性 
     */  
    private float floatAttr = 1.1f;  
  
    /* 
     * 定義一個布林型屬性 
     */  
    private boolean booleanAttr = true;  
  
    /* 
     * 定義一個空的屬性 
     */  
    private Address nullAttr = null;  
  
    /* 
     * 定義一個字元屬性 
     */  
    private char charAttr = 'j';  
  
    /* 
     * 定義一個包裝類整型屬性 
     */  
    private Integer intgerAttr = new Integer(2);  
  
    /* 
     * 定義一個字元屬性 
     */  
    private String strAttr = "jzj";  
  
    /* 
     * 定義一個引用其他Bean的屬性 
     */  
    private Address addrArr = new Address("changde", "lixian", 72452, "541-322-1723",  
            "546-338-1100");  
  
    /* 
     * 定義一個字元陣列屬性 
     */  
    private String[] strArrAttr = new String[] { "str1", "str2" };  
  
    /* 
     * 定義一個字元陣列屬性 
     */  
    private char[] charArrAttr = new char[] { 'j', 's', 'o', 'n' };  
  
    /* 
     * 定義一個list集合屬性 
     */  
    private List listAttr = new ArrayList();  
  
    /* 
     * 定義一個set集合屬性 
     */  
    private Set hasSetAttr = new HashSet();  
  
    /* 
     * 定義一個hashMap為存放陣列的map屬性，如果用 
     * org.json包轉換時則得不到正確有結果json-lib則可以 
     */  
    private Map hashMapAttr = new HashMap();  
  
    /** 
     * 構造器，初始化集合 
     */  
    public OtherBean() {  
        List tempList = new ArrayList();  
        tempList.add("one");  
        tempList.add("two");  
  
        listAttr.add("jiang");  
        listAttr.add(tempList);  
        listAttr.add(new Address("P.O BOX 54534", "Seattle, WA", 42452, "561-832-3180",  
                "531-133-9098"));  
  
        hasSetAttr.addAll(listAttr);  
  
        hashMapAttr.put("first", new String[][] { { "1", "2" }, { "3" } });  
        hashMapAttr.put("second", new String[][] { { "one", "two" }, { "three" } });  
    }  
        //以下是get set方法  
......  
}

package jsonlib;  
  
import java.io.BufferedOutputStream;  
import java.io.ByteArrayOutputStream;  
import java.io.IOException;  
import java.util.ArrayList;  
import java.util.Date;  
import java.util.LinkedHashMap;  
import java.util.List;  
import java.util.Map;  
  
import junit.framework.TestCase;  
import net.sf.ezmorph.bean.MorphDynaBean;  
import net.sf.json.JSONArray;  
import net.sf.json.JSONFunction;  
import net.sf.json.JSONObject;  
import net.sf.json.JsonConfig;  
import net.sf.json.xml.XMLSerializer;  
  
import org.dom4j.Document;  
import org.dom4j.DocumentException;  
import org.dom4j.DocumentHelper;  
import org.dom4j.io.OutputFormat;  
import org.dom4j.io.XMLWriter;  
  
import bean.Address;  
import bean.Bean;  
  
/** 
* 使用json-lib包進行bean、json、xml的資料轉換 
* (C) 2009-9-6,jzj 
*/  
public class JSONFormatTest extends TestCase {  
  
    public void testDate2Json() {  
  
        JSONObject jsonObj = JSONObject.fromObject(new Date());  
        // print: {"date":10,"day":4,"hours":2,"minutes":2,  
        //"month":8,"seconds":38,"time":1252519358062,"timezoneOffset":-480,"year":109}  
        System.out.println(jsonObj.toString());       
    }  
      
    public void testArray2Json() {  
  
        JSONArray jsonArr = JSONArray.fromObject(new String[][] { { "one", "two" },  
                { "three", "four" } });  
        // print: [["one","two"],["three","four"]]  
        System.out.println(jsonArr.toString());  
  
        //json串轉JSONArray  
        JSONArray jsArr = JSONArray.fromObject(jsonArr.toString());  
  
        //從JSONObject讀取資料  
        //print: three  
        System.out.println(((JSONArray) jsArr.get(1)).get(0));  
        System.out.println("/n");  
    }  
  
    public void testList2Json() {  
        List list = new ArrayList();  
        list.add(new Integer(1));  
        list.add(new Boolean(true));  
        list.add(new Character('j'));  
        list.add(new char[] { 'j', 's', 'o', 'n' });  
        list.add(null);  
        list.add("json");  
        list.add(new String[] { "json", "-", "lib" });  
        list.add(new JSONFunction(new String[] { "i" }, "alert(i)"));  
        list.add(new Address("P.O BOX 54534", "Seattle, WA", 42452, "561-832-3180",  
                "531-133-9098"));  
        //list轉JSONArray  
        JSONArray jsArr = JSONArray.fromObject(list);  
  
        /* 
        * list轉JSON串 
        * print: [1,true,"j",["j","s","o","n"],null,"json",["json","-","lib"], 
        * function(i){ alert(i) },{"city":"Seattle, WA","street":"P.O BOX 54534", 
        * "tel":"561-832-3180","telTwo":"531-133-9098","zip":42452}] 
        */  
        System.out.println(jsArr.toString(4));  
        //從JSON串到JSONArray  
        jsArr = JSONArray.fromObject(jsArr.toString());  
        //--從JSONArray裡讀取  
        //print: json  
        System.out.println(((JSONArray) jsArr.get(6)).get(0));  
        //print: address.city = Seattle, WA  
        System.out.println("address.city = " + ((JSONObject) jsArr.get(8)).get("city"));  
        System.out.println("/n");  
    }  
  
    public void testMap2Json() throws DocumentException {  
        Map map = new LinkedHashMap();  
        map.put("integer", new Integer(1));  
        map.put("boolean", new Boolean(true));  
        map.put("char", new Character('j'));  
        map.put("charArr", new char[] { 'j', 's', 'o', 'n' });  
        //注:不能以null為鍵名，否則執行報net.sf.json.JSONException: java.lang.NullPointerException:  
        //JSON keys must not be null nor the 'null' string.  
        map.put("nullAttr", null);  
  
        map.put("str", "json");  
        map.put("strArr", new String[] { "json", "-", "lib" });  
        map.put("jsonFunction", new JSONFunction(new String[] { "i" }, "alert(i)"));  
        map.put("address", new Address("P.O BOX 54534", "Seattle, WA", 42452,  
                "561-832-3180", "531-133-9098"));  
        //map轉JSONArray  
        JSONObject jsObj = JSONObject.fromObject(map);  
  
        /* 
        * map轉JSON串 
        *  
        * print:{"integer":1,"boolean":true,"char":"j","charArr":["j","s","o","n"], 
        * "nullAttr":null,"str":"json","strArr":["json","-","lib"],"jsonFunction": 
        * function(i){ alert(i) },"address":{"city":"Seattle, WA","street":"P.O BOX 54534", 
        * "tel":"561-832-3180","telTwo":"531-133-9098","zip":42452}} 
        */  
        System.out.println(jsObj.toString(4));  
        //從JSON串到JSONObject  
        jsObj = JSONObject.fromObject(jsObj.toString());  
  
        //--從JSONObject裡讀取  
        //print: json  
        System.out.println(jsObj.get("str"));  
        //print: address.city = Seattle, WA  
        System.out.println("address.city = "  
                + ((JSONObject) jsObj.get("address")).get("city"));  
  
        //--從動態Bean裡讀取資料，由於不能轉換成具體的Bean，感覺沒有多大用處  
        MorphDynaBean mdBean = (MorphDynaBean) JSONObject.toBean(jsObj);  
        //print: json  
        System.out.println(mdBean.get("str"));  
        //print: address.city = Seattle, WA  
        System.out.println("address.city = "  
                + ((MorphDynaBean) mdBean.get("address")).get("city"));  
  
        //--JSONObject轉XML  
        XMLSerializer xmlSerial = new XMLSerializer();  
        xmlSerial.setRootName("root");  
  
        /*注：轉換成XML元素key的名字要符合XML元素標籤的命名規則，否則會報 
        nu.xom.IllegalNameException: NCNames cannot start with the character 25異常 
         
        print:       
            <?xml version="1.0" encoding="UTF-8"?> 
            <root> 
                <address class="object"> 
                    <city type="string">Seattle, WA</city> 
                    <street type="string">P.O BOX 54534</street> 
                    <tel type="string">561-832-3180</tel> 
                    <telTwo type="string">531-133-9098</telTwo> 
                    <zip type="number">42452</zip> 
                </address> 
                <boolean type="boolean">true</boolean> 
                <char type="string">j</char> 
                <charArr class="array"> 
                    <e type="string">j</e> 
                    <e type="string">s</e> 
                    <e type="string">o</e> 
                    <e type="string">n</e> 
                </charArr> 
                <integer type="number">1</integer> 
                <jsonFunction type="function" params="i"></jsonFunctionAttr> 
                <listAttr class="array"> 
                    <e type="string">jiang</e> 
                    <e class="array"> 
                        <e type="string">one</e> 
                        <e type="string">two</e> 
                    </e> 
                    <e class="object"> 
                        <city type="string">Seattle, WA</city> 
                        <street type="string">P.O BOX 54534</street> 
                        <tel type="string">561-832-3180</tel> 
                        <telTwo type="string">531-133-9098</telTwo> 
                        <zip type="number">42452</zip> 
                    </e> 
                </listAttr> 
                <nullAttr class="object" null="true"/> 
                <strArrAttr class="array"> 
                    <e type="string">str1</e> 
                    <e type="string">str2</e> 
                </strArrAttr> 
                <strAttr type="string">jzj</strAttr> 
            </root> 
         */  
        System.out.println(write2XML(DocumentHelper.parseText(xmlSerial.write(jsonObj))));  
    }  
  
    private static String write2XML(Document doc) {  
  
        ByteArrayOutputStream cache = null;  
  
        try {  
            cache = new ByteArrayOutputStream(1024 * 512);  
  
            OutputFormat of = new OutputFormat();  
            of.setIndent(true);  
            of.setIndent(" ");  
            of.setIndentSize(4);  
            of.setNewlines(true);  
            BufferedOutputStream bos = new BufferedOutputStream(cache);  
            XMLWriter xmlWrite = new XMLWriter(bos, of);  
            xmlWrite.write(doc);  
            bos.close();  
            return cache.toString("UTF-8");  
        } catch (IOException e) {  
        }  
        return null;  
    }  
}

使用org.json進行轉換

package orgjson;  
  
import java.io.BufferedOutputStream;  
import java.io.ByteArrayOutputStream;  
import java.io.IOException;  
import java.util.ArrayList;  
import java.util.Iterator;  
import java.util.LinkedHashMap;  
import java.util.List;  
import java.util.Map;  
  
import junit.framework.TestCase;  
import net.sf.json.JSONFunction;  
  
import org.dom4j.Document;  
import org.dom4j.DocumentException;  
import org.dom4j.DocumentHelper;  
import org.dom4j.io.OutputFormat;  
import org.dom4j.io.XMLWriter;  
import org.json.JSONArray;  
import org.json.JSONException;  
import org.json.JSONObject;  
import org.json.XML;  
  
import bean.Address;  
import bean.Bean;  
  
/** 
* 使用org.json包進行bean、json、xml的資料轉換 
* (C) 2009-9-6,jzj 
*/  
public class JSONFormatTest extends TestCase {  
  
    public void testArray2Json() throws JSONException {  
  
        JSONArray jsonArr = new JSONArray(new String[][] { { "one", "two" },  
                { "three", "four" } });  
        // print: [["one","two"],["three","four"]]  
        System.out.println(jsonArr.toString());  
  
        //json串轉JSONArray  
        JSONArray jsArr = new JSONArray(jsonArr.toString());  
  
        //從JSONObject讀取資料  
        //print: three  
        System.out.println(((JSONArray) jsArr.get(1)).get(0));  
        System.out.println("/n");  
    }  
  
    public void testList2Json() throws JSONException {  
        List list = new ArrayList();  
        list.add(new Integer(1));  
        list.add(new Boolean(true));  
        list.add(new Character('j'));  
        list.add(new char[] { 'j', 's', 'o', 'n' });  
        list.add(null);  
        list.add("json");  
        list.add(new String[] { "json", "-", "lib" });  
        list.add(new JSONFunction(new String[] { "i" }, "alert(i)"));  
        list.add(new Address("P.O BOX 54534", "Seattle, WA", 42452, "561-832-3180",  
                "531-133-9098"));  
        //list轉JSONArray  
        JSONArray jsArr = new JSONArray(list);  
  
        /* 
        * list轉JSON串 
        * print: 
            [ 
                1, 
                true, 
                "j", 
                [ 
                    "j", 
                    "s", 
                    "o", 
                    "n" 
                ], 
                null, 
                "json", 
                [ 
                    "json", 
                    "-", 
                    "lib" 
                ], 
                "function(i){ alert(i) }", 
                "bean.Address@1cf8583" 
            ] 
 
        * 注：org.json不支援list中非JSON物件與陣列物件外的物件，會直接呼叫物件的toString方法 
        */  
        System.out.println(jsArr.toString(4));  
        //從JSON串到JSONArray  
        JSONArray jsArr1 = new JSONArray(jsArr.toString());  
  
        //--從JSONArray裡讀取  
        //print: json  
        System.out.println(((JSONArray) jsArr1.get(6)).get(0));  
  
        //不能正確讀取物件的資訊 print: address.city = bean.Address@1cf8583  
        System.out.println("address.city = " + jsArr1.get(8));  
        System.out.println("/n");  
    }  
  
    public void testMap2Json() throws JSONException, DocumentException {  
        Map map = new LinkedHashMap();  
        map.put("integer", new Integer(1));  
        map.put("boolean", new Boolean(true));  
        map.put("char", new Character('j'));  
        map.put("charArr", new char[] { 'j', 's', 'o', 'n' });  
        map.put("null", null);  
        map.put("str", "json");  
        map.put("strArr", new String[] { "json", "-", "lib" });  
        map.put("jsonFunction", new JSONFunction(new String[] { "i" }, "alert(i)"));  
        map.put("address", new Address("P.O BOX 54534", "Seattle, WA", 42452,  
                "561-832-3180", "531-133-9098"));  
        //map轉JSONArray  
        JSONObject jsObj = new JSONObject(map);  
  
        /* 
        * map轉JSON串 
        * print: 
        { 
            "address": "bean.Address@1cf8583", 
            "boolean": true, 
            "char": "j", 
            "charArr": [ 
                "j", 
                "s", 
                "o", 
                "n" 
            ], 
            "integer": 1, 
            "jsonFunction": "function(i){ alert(i) }", 
            "null": null, 
            "str": "json", 
            "strArr": [ 
                "json", 
                "-", 
                "lib" 
            ] 
        } 
        */  
        System.out.println(jsObj.toString(4));  
        //從JSON串到JSONObject  
        jsObj = new JSONObject(jsObj.toString());  
        //--從JSONObject裡讀取  
        //print: json  
        System.out.println(jsObj.get("str"));  
        //print: address.city = Seattle, WA  
        System.out.println("address.city = " + jsObj.get("address"));  
  
        //--org.json不支援從JSONObject到Bean的轉換  
        //MorphDynaBean mdBean = (MorphDynaBean) JSONObject.toBean(jsObj);  
  
        //--JSONObject轉XML  
        //print:  
        /* 
            <root> 
                <null>null</null> 
                <char>j</char> 
                <integer>1</integer> 
                <address>bean.Address@901887</address> 
                <strArr>json</strArr> 
                <strArr>-</strArr> 
                <strArr>lib</strArr> 
                <charArr>j</charArr> 
                <charArr>s</charArr> 
                <charArr>o</charArr> 
                <charArr>n</charArr> 
                <jsonFunction>function(i){ alert(i) }</jsonFunction> 
                <str>json</str> 
                <boolean>true</boolean> 
            </root> 
         */  
        System.out.println(write2XML(DocumentHelper  
                .parseText(XML.toString(jsObj, "root"))));  
        System.out.println("/n");  
    }  
  
    /** 
    * 如果某個Bean裡含有Map屬性，且Map裡存放的為陣列，此時需要對Map裡的陣列進一步用 
    * JSONArray包裝後才能輸出正確結果 
    * @throws JSONException 
    */  
    public void testBeanToJsonStr() throws JSONException {  
        Bean bean = new Bean();  
        JSONObject jsonObj = new JSONObject(bean);  
        try {  
  
            /* 如果不用JSONArray進行包裝轉換，則不能得到正確結果，其關鍵原因是：如果Bean的某屬性 
            * 所對應的屬性型別為Map時，轉換Map中的值所對就程式碼如下： 
            *  } else if (result instanceof Map) { 
            *      map.put(key, new JSONObject((Map)result, includeSuperClass)); 
            * 由於上述程式碼陣列轉換成了JSONObject物件了，對應的應該JSONArray 
            */  
            System.out.println(jsonObj.toString(4));  
              
            //--以下是正確作法  
            //得到Bean的Map屬性值  
            Map hashMapAttr = bean.getHashMapAttr();  
            //對hashMap屬性用JSONArray進行包裝  
            Iterator it = hashMapAttr.entrySet().iterator();  
  
            //Bean中hashMap屬性值轉換成map2JsonObj  
            JSONObject map2JsonObj = new JSONObject();  
            while (it.hasNext()) {  
                Map.Entry entry = (Map.Entry) it.next();  
                map2JsonObj.put((String) entry.getKey(), new JSONArray(entry.getValue()));  
            }  
  
            //置換掉Bean中hashMap屬性原有的map物件值，置換後hashMap屬性的值為JSONObject物件例項，  
            //而JSONObject物件例項儲存了原hashMap中所對應值的所有資訊  
            jsonObj.put("hashMap", map2JsonObj);  
            System.out.println(jsonObj.toString(4));  
  
            //json轉JSONObject  
            jsonObj = new JSONObject(jsonObj.toString());  
            //print:Seattle, WA  
            System.out.println(((JSONObject) ((JSONArray) jsonObj.get("hasSetAttr"))  
                    .get(2)).get("city"));  
  
            //--Bean轉XML  
            //print:  
            System.out.println(XML.toString(jsonObj, "root"));  
  
        } catch (JSONException e) {  
            e.printStackTrace();  
        }  
    }  
  
    private static String write2XML(Document doc) {  
  
        ByteArrayOutputStream cache = null;  
  
        try {  
            cache = new ByteArrayOutputStream(1024 * 512);  
  
            OutputFormat of = new OutputFormat();  
            of.setIndent(true);  
            of.setIndent(" ");  
            of.setIndentSize(4);  
            of.setNewlines(true);  
            BufferedOutputStream bos = new BufferedOutputStream(cache);  
            XMLWriter xmlWrite = new XMLWriter(bos, of);  
            xmlWrite.write(doc);  
            bos.close();  
            return cache.toString("UTF-8");  
        } catch (IOException e) {  
        }  
        return null;  
    }  
}

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