JSON解析之Json-lib
1.Json-lib介绍
Json-lib是一个java类库，它用于把beans, maps, collections, java arrays and XML 传递给一个Json，或者返回来把Json来传递beans, maps, collections, java arrays and XML ，说白了就是用于处理JSON数据的，包括生成和解析过程。这个时候你肯定会疑惑那么Javascript中JSON数据类型和Java中的数据类型是如何对应起来的额，不过不用担心，下面就给出了他们之间的对应关系。
| JSON | Java | |
|---|---|---|
| string | <=> | java.lang.String, java.lang.Character, char |
| number | <=> | java.lang.Number, byte, short, int, long, float, double |
| true|false | <=> | java.lang.Boolean, boolean |
| null | <=> | null |
| function | <=> | net.sf.json.JSONFunction |
| array | <=> | net.sf.json.JSONArray (object, string, number, boolean, function) |
| object | <=> | net.sf.json.JSONObject |
需要支出的是：虽然Javascript中的function类型不是JSON的官方格式，可是这个也是支持的。
2.Json-lib相关依赖
Json-lib除了依赖自身的jar包以外还依赖一些其他的jar包，最新的版本是json-lib-2.4-jdk15，初次之外还需要最小依赖的其他jar包有
jakarta commons-lang 2.5
jakarta commons-beanutils 1.8.0
jakarta commons-collections 3.2.1
jakarta commons-logging 1.1.1
ezmorph 1.0.6
这个只是最小依赖的jar包，完整依赖的jar包包括
jakarta commons-lang 2.5
jakarta commons-beanutils 1.8.0
jakarta commons-collections 3.2.1
jakarta commons-logging 1.1.1
ezmorph 1.0.6
commons-httpclient-3.1.jar
groovy-all-1.7.5.jar
junit-3.8.2.jar
log4j-1.2.14.jar
oro-2.0.8.jar
xmlunit-1.0.jar
xom-1.1.jar
其他方式，如果使用的maven来作为项目管理工具，那么只需要在pom.xml中加上
<dependency> <groupId>net.sf.json-lib</groupId> <artifactId>json-lib</artifactId> <version>2.4</version> </dependency>
即可，如果是Gradle那么只需要加上
'net.sf.json-lib:json-lib:2.4'
就可以了，这样就可以把所有相关依赖的jar包加进去了。在添加jar包的时候需要注意各个jar包的版本，如果版本不匹配就会出现问题，所以建议使用maven或者gradle来管理项目，这样就可以避免因为版本问题不匹配而引起的问题了，既然完成了jar包的引入，那么就可以开始使用Json-lib了。
3.主要对象介绍及使用
a:JSONSerializer
JSONSerializer可以任何java对象转换为JSON, 这样就能够方法JSONObject和JSONArray使用了。如果将一个java对象传给Json可以使用JSONSerializer.toJSON()，将一个合法的json传给一个Java对象可以使用JSONSerializer.toJava()
import java.util.Date; public class Book { int id; int price; String name; String author; Date publishDate; public int getId() { return id; } public void setId(int id) { this.id = id; } public int getPrice() { return price; } public void setPrice(int price) { this.price = price; } public String getAuthor() { return author; } public void setAuthor(String author) { this.author = author; } public Date getPublishDate() { return publishDate; } public void setPublishDate(Date publishDate) { this.publishDate = publishDate; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { // TODO Auto-generated method stub return "name:"+this.name+",author:"+this.author+",id:"+this.id+",price:"+this.price+",publishDate:"+this.publishDate.toLocaleString(); } }
import java.util.Date; import net.sf.json.JSON; import net.sf.json.JSONSerializer; public class JSONSerializerTest { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub Book book = new Book(); book.setId(1); book.setName("java编程要领"); book.setPrice(12); book.setAuthor("tomas"); book.setPublishDate(new Date()); System.out.println("JSONSerializer.toJSON()方法"); JSON json = JSONSerializer.toJSON(book); System.out.println(json); String jsonStr = "{author=\"tomas\",id:1,price:12,publishDate:\"\"}"; System.out.println("JSONSerializer.toJava()方法"); Object tempObj = JSONSerializer.toJava(json); System.out.println(Object.class.cast(book).toString()); } }
结果
JSONSerializer.toJSON()方法 {"author":"tomas","id":1,"name":"java编程要领","price":12,"publishDate":{"date":19,"day":3,"hours":11,"minutes":40,"month":10,"seconds":43,"time":1416368443978,"timezoneOffset":-480,"year":114}} JSONSerializer.toJava()方法 name:java编程要领,author:tomas,id:1,price:12,publishDate:2014-11-19 11:40:43
b.处理数组和集合
主要通过JSONArray.fromObject(arr)这个方法获取JSONArray，进而对其进行操作，帖代码（用到的实体Book和上面是一样的）
HandleArrAndCollection.java
import java.util.ArrayList; import java.util.Date; import java.util.List; import net.sf.json.JSONArray; public class HandleArrAndCollection { public static void main(String[] args) { int []arr = {12,334,54,677,8,3}; JSONArray jsonArray = JSONArray.fromObject(arr); System.out.println(jsonArray); List<Book> list = new ArrayList<Book>(); for(int index = 0;index < 10;index++){ Book book = new Book(); book.setId(index); book.setAuthor("author"+index); book.setName("name"+index); book.setPrice(21+index); book.setPublishDate(new Date()); list.add(book); } JSONArray jsonList = JSONArray.fromObject(list); System.out.println(jsonList); } }
输出的结果效果：
将数组转为JSON对象 [12,334,54,677,8,3] 将List转为JSON对象 [{"author":"author0","id":0,"name":"name0","price":21,"publishDate":{"date":19,"day":3,"hours":17,"minutes":31,"month":10,"seconds":47,"time":1416389507482,"timezoneOffset":-480,"year":114}},{"author":"author1","id":1,"name":"name1","price":22,"publishDate":{"date":19,"day":3,"hours":17,"minutes":31,"month":10,"seconds":47,"time":1416389507482,"timezoneOffset":-480,"year":114}},{"author":"author2","id":2,"name":"name2","price":23,"publishDate":{"date":19,"day":3,"hours":17,"minutes":31,"month":10,"seconds":47,"time":1416389507482,"timezoneOffset":-480,"year":114}},{"author":"author3","id":3,"name":"name3","price":24,"publishDate":{"date":19,"day":3,"hours":17,"minutes":31,"month":10,"seconds":47,"time":1416389507482,"timezoneOffset":-480,"year":114}},{"author":"author4","id":4,"name":"name4","price":25,"publishDate":{"date":19,"day":3,"hours":17,"minutes":31,"month":10,"seconds":47,"time":1416389507482,"timezoneOffset":-480,"year":114}},{"author":"author5","id":5,"name":"name5","price":26,"publishDate":{"date":19,"day":3,"hours":17,"minutes":31,"month":10,"seconds":47,"time":1416389507482,"timezoneOffset":-480,"year":114}},{"author":"author6","id":6,"name":"name6","price":27,"publishDate":{"date":19,"day":3,"hours":17,"minutes":31,"month":10,"seconds":47,"time":1416389507482,"timezoneOffset":-480,"year":114}},{"author":"author7","id":7,"name":"name7","price":28,"publishDate":{"date":19,"day":3,"hours":17,"minutes":31,"month":10,"seconds":47,"time":1416389507482,"timezoneOffset":-480,"year":114}},{"author":"author8","id":8,"name":"name8","price":29,"publishDate":{"date":19,"day":3,"hours":17,"minutes":31,"month":10,"seconds":47,"time":1416389507482,"timezoneOffset":-480,"year":114}},{"author":"author9","id":9,"name":"name9","price":30,"publishDate":{"date":19,"day":3,"hours":17,"minutes":31,"month":10,"seconds":47,"time":1416389507482,"timezoneOffset":-480,"year":114}}]
c.JSON处理对象
主要通过JSONObject.fromObject( )，来实现，可以传递的参数有Map,Bean,JSON字符串，也就是一个对象Object
HandleObjects.java
import java.lang.reflect.InvocationTargetException; import java.util.Date; import java.util.HashMap; import java.util.List; import java.util.Map; import junit.framework.Assert; import org.apache.commons.beanutils.PropertyUtils; import net.sf.json.JSONArray; import net.sf.json.JSONObject; public class HandleObjects { /** * @param args * @throws NoSuchMethodException * @throws InvocationTargetException * @throws IllegalAccessException */ public static void main(String[] args) throws IllegalAccessException, InvocationTargetException, NoSuchMethodException { System.out.println( "Map对象转JSONJSON" ); Map<String,Object> map = new HashMap<String,Object>(); map.put( "name", "json" ); map.put( "bool", Boolean.TRUE ); map.put( "int", new Integer(1) ); map.put( "arr", new String[]{"a","b"} ); map.put( "func", "function(i){ return this.arr[i]; }" ); JSONObject jsonObject1 = JSONObject.fromObject( map ); System.out.println( jsonObject1 ); System.out.println( "Bean转JSON" ); Book book = new Book(); book.setId(1); book.setName("java编程语言"); book.setPrice(12); book.setAuthor("tomas"); book.setPublishDate(new Date()); JSONObject jsonObj2 = JSONObject.fromObject( book ); System.out.println( jsonObj2 ); System.out.println( "JSON转为BEAN" ); String json = "{name=\"json\",bool:true,int:1,double:2.2,func:function(a){ return a; },array:[1,2]}"; JSONObject jsonObject = JSONObject.fromObject( json ); Object bean = JSONObject.toBean( jsonObject ); System.out.println(jsonObject.get( "name" )); System.out.println(PropertyUtils.getProperty( bean, "name" ) ); System.out.println(jsonObject.get( "bool" )); System.out.println(PropertyUtils.getProperty( bean, "bool" ) ); System.out.println(jsonObject.get( "int" )); System.out.println(PropertyUtils.getProperty( bean, "int" ) ); System.out.println(jsonObject.get( "double" )); System.out.println(PropertyUtils.getProperty( bean, "double" ) ); System.out.println(jsonObject.get( "func" )); System.out.println(PropertyUtils.getProperty( bean, "func" ) ); } }
输出的结果：
Map对象转JSONJSON {"arr":["a","b"],"int":1,"name":"json","func":function(i){ return this.arr[i]; },"bool":true} Bean转JSON {"author":"tomas","id":1,"name":"java编程语言","price":12,"publishDate":{"date":19,"day":3,"hours":17,"minutes":38,"month":10,"seconds":35,"time":1416389915909,"timezoneOffset":-480,"year":114}} JSON转为BEAN json json true true 1 1 2.2 2.2 function(a){ return a; } function(a){ return a; }
d：处理XML
使用起来也比较简单，主要是获取XML对应的JSON对象，然后通过Json-lib提供的XMLSerializer方法来进行处理（它的很多方法是非静态的需要首先实例化）
HandleXML.java
import java.io.File; import net.sf.json.JSONArray; import net.sf.json.JSONObject; import net.sf.json.xml.XMLSerializer; public class HandleXML { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub JSONObject json = new JSONObject( true ); XMLSerializer xmlSerializer = new XMLSerializer(); String xml = xmlSerializer.write( json ); System.out.println("构建简单XML文件"); System.out.println(xml); JSONObject json2 = JSONObject.fromObject("{\"name\":\"json\",\"bool\":true,\"int\":1}"); String xml2 = new XMLSerializer().write( json2 ); System.out.println("构建稍复杂XML文件"); System.out.println(xml2); JSONArray json3 = JSONArray.fromObject("[1,2,3]"); String xml3 = new XMLSerializer().write( json3 ); System.out.println("构建数字XML文件"); System.out.println(xml3); JSONArray json4 = (JSONArray) new XMLSerializer().readFromFile(new File("src/json.xml")); System.out.println("通过JSON解析XML文件"); System.out.println( json4 ); } }
输出结果：
构建简单XML文件 <?xml version="1.0" encoding="UTF-8"?> <o null="true"/> 构建稍复杂XML文件 <?xml version="1.0" encoding="UTF-8"?> <o><bool type="boolean">true</bool><int type="number">1</int><name type="string">json</name></o> 构建数字XML文件 <?xml version="1.0" encoding="UTF-8"?> <a><e type="number">1</e><e type="number">2</e><e type="number">3</e></a> 通过JSON解析XML文件 [{"id":"1","name":"Java编程","price":"23","author":"Wudy"},{"id":"1","name":"Java编程","price":"23","author":"Wudy"}]
使用的XML文件为：json.xml
<?xml version="1.0" encoding="UTF-8"?> <root> <book> <id>1</id> <name>Java编程</name> <price>23</price> <author>Wudy</author> </book> <book> <id>1</id> <name>Java编程</name> <price>23</price> <author>Wudy</author> </book> </root>
4.总结
通过上面的程序可以看出，使用Json-lib来处理JSON时无论是生成还是解析，用到的方法都比较简单，主要用到的对象就是JSONObject以及JSONArray，在处理XML文件时用到了XMLSerializer，总的来说很容易上手使用，比较简单，下篇文章介绍Gson,另外一个开源类库用来处理JSON，由Google提供的。
