JSON — Java与JSON数据互转

 

转换时Bean所要求的：

• 被转换的Bean必需是public的。
• Bean被转换的属性一定要有对应的get方法，且一定要是public的。
• Bean中不能用引用自身的this的属性，否则运行时出现et.sf.json.JSONException: There is a cycle in the hierarchy!异常
• json-lib包转换时，不能以null为键名，否则运行报net.sf.json.JSONException:java.lang.NullPointerException:JSON keys must not be null nor the 'null' string.
• json-lib包转换时， 转换成XML元素key的名字要符合XML元素标签的命名规则，否则会报nu.xom.IllegalNameException: NCNames cannot start with the character 25异常
  

转换时问题：

• 如果某个Bean中存在存放数组的Map属性，则使用org.json包中的JSONObject直接封装时得不到正确的JSON，要用JSONArray对数组进行封装处理，否则为转换JavaScript中的空的对象{}，但能使用json-lib包很好地解决这一问题

两种包的比较：

• json-lib包比org.json要易使用些，至少没有烦人的JSONExcetipn捕获异常了。
• json-lib对Bean的支持比org.json要强，特别是对bean中内嵌属性的支持较好。

json-lib依赖包：

1.   commons-beanutils-1.8.0.jar
2.   commons-collections-3.2.1.jar
3.   commons-lang-2.4.jar
4.   commons-logging-1.1.1.jar
5.   ezmorph-1.0.6.jar
6.   json-lib-2.3-jdk15.jar
7.   xom-1.2.2.jar

• 实例所用到的三个Bean

 

 

 

Java代码 

package bean; /** * 创建Address实体类的POJO * (C) 2009-9-1, jzj */ public class Address { private String street;//街道 private String city;//城市 private int zip;//邮编 private String tel;//第一个电话号码 private String telTwo;//第二个电话号码 public Address() { } public Address(String street, String city, int zip, String tel, String telTwo) { this.street = street; this.city = city; this.zip = zip; this.tel = tel; this.telTwo = telTwo; } //以下是get set 方法 ...... }  

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 定义各种类型的属性，便于测试 * (C) 2009-9-7, jzj */ public class OtherBean { /* * 定义一个整数属性 */ private int intAttr = 1; /* * 定义一个浮点数属性 */ private float floatAttr = 1.1f; /* * 定义一个布尔型属性 */ private boolean booleanAttr = true; /* * 定义一个空的属性 */ private Address nullAttr = null; /* * 定义一个字符属性 */ private char charAttr = 'j'; /* * 定义一个包装类整型属性 */ private Integer intgerAttr = new Integer(2); /* * 定义一个字符属性 */ private String strAttr = "jzj"; /* * 定义一个引用其他Bean的属性 */ private Address addrArr = new Address("changde", "lixian", 72452, "541-322-1723", "546-338-1100"); /* * 定义一个字符数组属性 */ private String[] strArrAttr = new String[] { "str1", "str2" }; /* * 定义一个字符数组属性 */ private char[] charArrAttr = new char[] { 'j', 's', 'o', 'n' }; /* * 定义一个list集合属性 */ private List listAttr = new ArrayList(); /* * 定义一个set集合属性 */ private Set hasSetAttr = new HashSet(); /* * 定义一个hashMap为存放数组的map属性，如果用 * org.json包转换时则得不到正确有结果json-lib则可以 */ private Map hashMapAttr = new HashMap(); /** * 构造器，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 bean; import java.util.ArrayList; import java.util.Date; import java.util.HashMap; import java.util.HashSet; import java.util.List; import java.util.Map; import java.util.Set; import net.sf.json.JSONFunction; /** * POJO 定义各种类型的属性，便于测试 * (C) 2009-9-7, jzj */ public class Bean { //其他属性略，在OtherBean的基础上加上了otherBeanAttr属性而已 ...... /* * 定义一个引用复杂实例的属性，这样可以测试属性递归情况 * print：以上各属性值 */ private OtherBean otherBeanAttr = new OtherBean(); //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包进行bean、json、xml的数据转换 * (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串转JSONArray JSONArray jsArr = JSONArray.fromObject(jsonArr.toString()); //从JSONObject读取数据 //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转JSONArray JSONArray jsArr = JSONArray.fromObject(list); /* * list转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)); //从JSON串到JSONArray jsArr = JSONArray.fromObject(jsArr.toString()); //--从JSONArray里读取 //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为键名，否则运行报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转JSONArray JSONObject jsObj = JSONObject.fromObject(map); /* * map转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)); //从JSON串到JSONObject jsObj = JSONObject.fromObject(jsObj.toString()); //--从JSONObject里读取 //print: json System.out.println(jsObj.get("str")); //print: address.city = Seattle, WA System.out.println("address.city = " + ((JSONObject) jsObj.get("address")).get("city")); //--从动态Bean里读取数据，由于不能转换成具体的Bean，感觉没有多大用处 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转XML XMLSerializer xmlSerial = new XMLSerializer(); xmlSerial.setRootName("root"); /*注：转换成XML元素key的名字要符合XML元素标签的命名规则，否则会报 nu.xom.IllegalNameException: NCNames cannot start with the character 25异常 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"><!--[CDATA[alert(i)]]></jsonFunction> <nullAttr class="object" null="true"/> <str type="string">json</str> <strArr class="array"> <e type="string">json</e> <e type="string">-</e> <e type="string">lib</e> </strArr> </root> */ System.out.println(write2XML(DocumentHelper.parseText(xmlSerial.write(jsObj)))); System.out.println("/n"); } public void testBean2Json() throws DocumentException { Bean bean = new Bean(); JSONObject jsonObj = JSONObject.fromObject(bean); /*print: { "booleanAttr": true, "charArrAttr": [ "j", "s", "o", "n" ], "charAttr": "j", "floatAttr": 1.1, "hasSetAttr": [ "jiang", [ "one", "two" ], { "city": "Seattle, WA", "street": "P.O BOX 54534", "tel": "561-832-3180", "telTwo": "531-133-9098", "zip": 42452 } ], "hashMapAttr": { "first": [ [ "1", "2" ], ["3"] ], "second": [ [ "one", "two" ], ["three"] ] }, "intAttr": 1, "intgerAttr": 2, "jsonFunctionAttr": function(name){ alert(name) }, "listAttr": [ "jiang", [ "one", "two" ], { "city": "Seattle, WA", "street": "P.O BOX 54534", "tel": "561-832-3180", "telTwo": "531-133-9098", "zip": 42452 } ], "nullAttr": null, "otherBeanAttr": { "addrArr": { "city": "lixian", "street": "changde", "tel": "541-322-1723", "telTwo": "546-338-1100", "zip": 72452 }, "booleanAttr": true, "charArrAttr": [ "j", "s", "o", "n" ], "charAttr": "j", "floatAttr": 1.1, "hasSetAttr": [ { "city": "Seattle, WA", "street": "P.O BOX 54534", "tel": "561-832-3180", "telTwo": "531-133-9098", "zip": 42452 }, [ "one", "two" ], "jiang" ], "hashMapAttr": { "first": [ [ "1", "2" ], ["3"] ], "second": [ [ "one", "two" ], ["three"] ] }, "intAttr": 1, "intgerAttr": 2, "listAttr": [ "jiang", [ "one", "two" ], { "city": "Seattle, WA", "street": "P.O BOX 54534", "tel": "561-832-3180", "telTwo": "531-133-9098", "zip": 42452 } ], "nullAttr": null, "strArrAttr": [ "str1", "str2" ], "strAttr": "jzj" }, "strArrAttr": [ "str1", "str2" ], "strAttr": "jzj" } */ System.out.println(jsonObj.toString(4)); //json转JSONObject jsonObj = JSONObject.fromObject(jsonObj.toString()); //print:Seattle, WA System.out.println(((JSONObject) ((JSONArray) jsonObj.get("hasSetAttr")).get(2)) .get("city")); //--JSONObject转Bean bean = (Bean) JSONObject.toBean(jsonObj, Bean.class); //注:如果Bean里的某个属性存有数组，则数组转换成list存放，但如果数组为bean属性时转换后还是数组 //print: 1 System.out.println(((List) ((List) bean.getHashMapAttr().get("first")).get(0)) .get(0)); //print: j System.out.println(((char[]) bean.getCharArrAttr())[0]); //--Bean转XML XMLSerializer xmlSerial = new XMLSerializer(); //设置根节点名 xmlSerial.setRootName("root"); JsonConfig jc = new JsonConfig(); //排除不需要转换的属性，排除otherBeanAttr内部引用属性 jc.setExcludes(new String[] { "otherBeanAttr" }); jsonObj = JSONObject.fromObject(bean, jc); /* print: <?xml version="1.0" encoding="UTF-8"?> <root> <booleanAttr type="boolean">true</booleanAttr> <charArrAttr class="array"> <e type="string">j</e> <e type="string">s</e> <e type="string">o</e> <e type="string">n</e> </charArrAttr> <charAttr type="string">j</charAttr> <floatAttr type="number">1.1</floatAttr> <hasSetAttr 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> </hasSetAttr> <hashMapAttr class="object"> <first class="array"> <e class="array"> <e type="string">1</e> <e type="string">2</e> </e> <e class="array"> <e type="string">3</e> </e> </first> <second class="array"> <e class="array"> <e type="string">one</e> <e type="string">two</e> </e> <e class="array"> <e type="string">three</e> </e> </second> </hashMapAttr> <intAttr type="number">1</intAttr> <intgerAttr type="number">2</intgerAttr> <jsonFunctionAttr type="function" params="name"><![CDATA[alert(name)]]--></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进行转换

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包进行bean、json、xml的数据转换 * (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串转JSONArray JSONArray jsArr = new JSONArray(jsonArr.toString()); //从JSONObject读取数据 //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转JSONArray JSONArray jsArr = new JSONArray(list); /* * list转JSON串 * print: [ 1, true, "j", [ "j", "s", "o", "n" ], null, "json", [ "json", "-", "lib" ], "function(i){ alert(i) }", "bean.Address@1cf8583" ] * 注：org.json不支持list中非JSON对象与数组对象外的对象，会直接调用对象的toString方法 */ System.out.println(jsArr.toString(4)); //从JSON串到JSONArray JSONArray jsArr1 = new JSONArray(jsArr.toString()); //--从JSONArray里读取 //print: json System.out.println(((JSONArray) jsArr1.get(6)).get(0)); //不能正确读取对象的信息 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转JSONArray JSONObject jsObj = new JSONObject(map); /* * map转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)); //从JSON串到JSONObject jsObj = new JSONObject(jsObj.toString()); //--从JSONObject里读取 //print: json System.out.println(jsObj.get("str")); //print: address.city = Seattle, WA System.out.println("address.city = " + jsObj.get("address")); //--org.json不支持从JSONObject到Bean的转换 //MorphDynaBean mdBean = (MorphDynaBean) JSONObject.toBean(jsObj); //--JSONObject转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"); } /** * 如果某个Bean里含有Map属性，且Map里存放的为数组，此时需要对Map里的数组进一步用 * JSONArray包装后才能输出正确结果 * @throws JSONException */ public void testBeanToJsonStr() throws JSONException { Bean bean = new Bean(); JSONObject jsonObj = new JSONObject(bean); try { /* 如果不用JSONArray进行包装转换，则不能得到正确结果，其关键原因是：如果Bean的某属性 * 所对应的属性类型为Map时，转换Map中的值所对就代码如下： * } else if (result instanceof Map) { * map.put(key, new JSONObject((Map)result, includeSuperClass)); * 由于上述代码数组转换成了JSONObject对象了，对应的应该JSONArray */ System.out.println(jsonObj.toString(4)); //--以下是正确作法 //得到Bean的Map属性值 Map hashMapAttr = bean.getHashMapAttr(); //对hashMap属性用JSONArray进行包装 Iterator it = hashMapAttr.entrySet().iterator(); //Bean中hashMap属性值转换成map2JsonObj JSONObject map2JsonObj = new JSONObject(); while (it.hasNext()) { Map.Entry entry = (Map.Entry) it.next(); map2JsonObj.put((String) entry.getKey(), new JSONArray(entry.getValue())); } //置换掉Bean中hashMap属性原有的map对象值，置换后hashMap属性的值为JSONObject对象实例， //而JSONObject对象实例存储了原hashMap中所对应值的所有信息 jsonObj.put("hashMap", map2JsonObj); System.out.println(jsonObj.toString(4)); //json转JSONObject jsonObj = new JSONObject(jsonObj.toString()); //print:Seattle, WA System.out.println(((JSONObject) ((JSONArray) jsonObj.get("hasSetAttr")) .get(2)).get("city")); //--Bean转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; } }