json lib 学习笔记

json-lib demo

JSON-lib这个Java类包用于把bean,map和XML转换成JSON并能够把JSON转回成bean和DynaBean。
到http://json-lib.sourceforge.net下载json-lib-1.1-jdk15.jar，运行json还需要的包有：
jakarta commons-lang 2.4.jar
jakarta commons-beanutils 1.7.0.jar
jakarta commons-collections 3.2.jar
jakarta commons-logging 1.1.1.jar
ezmorph 1.0.6.jar
可在http://www.docjar.com上搜索下载。

 

javaScript与java对象之间的对应关系

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

 

1. 将java数组和java集合转化成一个json数组
通过静态工厂方法JSONArray.fromObject()将一个java数组或集合转化成一个json数组对象JSONArray.
实例1:转化java数组

String [] array = {"a","d","1","b"};
JSONArray jsonArray = JSONArray.fromObject(array);
System.out.println(jsonArray);

 输出结果：["a","d","1","b"]//注意他们的顺序与java数组中的顺序是一致的。

 

实例2：转化List对象

String [] array = {"d","a","1","b"};
List list = new ArrayList();   
list.add( array );   
list.add( "second element");  
JSONArray jsonArray = JSONArray.fromObject(list);
System.out.println(jsonArray);

 输出结果：[["d","a","1","b"],"second element"]

实例3：转化字符串

String test = "['json','is','easy']";
JSONArray jsonArray = JSONArray.fromObject( test );   
System.out.println(jsonArray); 

 

使用JSONArray.fromObject()转化字符串时，字符串必须符合JSONArray的格式。

2.将Map或javaBean转化成JSONObject
实例４：转化Map

Map map = new HashMap();
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 json = JSONObject.fromObject(map);
System.out.println(json);

 输出：[“name”: “json”, “bool”:true, “int”,1, “arr”:[ “a”, “b”], “func”:function(i){return this.arr[i];}]

实例５：转化javaBean

public class TestBean {
	private String id;
	private String name;
	private int age;
	private String email;
	public TestBean() { 
   }
  public TestBean(String id, String name, int age, String email) {
	    super();
	    this.id = id;
	    this.name = name;
	    this.age = age;
	    this.email = email;
  }
 //以下为get、set方法
}

 输出:{"age":36,"email":"","id":"2","name":"xxhh"}
//这是一个json object，其实就是一个javascript对象。注意其中属性的顺序，是排过序的。

3.将JSONObject转化为javaBean对象
实例６:

String myJson = "{'age':36,'email':'','id':'2','name':'testName'}";
JSONObject jsonObject1 = JSONObject.fromObject( myJson );   
TestBean bean = (TestBean) JSONObject.toBean( jsonObject1, TestBean.class );   
System.out.println("beanName:" + bean.getName());

 输出：beanName:testName

 

4.将JSONArray转化为list对象:

实例7:

ExampleBean对象的代码如下:

public class ExampleBean {
private String	name;
	private String	id;
	private int	   age;
public ExampleBean() {
		super();
	}
public ExampleBean(String name, String id, int age) {
		super();
		this.name = name;
		this.id = id;
		this.age = age;
	}
//getter和setter方法
}

  测试代码:

public class Test {

	public static void main(String[] args) {
		List<ExampleBean> list1 = new ArrayList<ExampleBean>();
		for (int i = 0; i < 5; i++) {
			String name = "xxlong" + i;
			int age = 20 + i;
			ExampleBean bean = new ExampleBean(name, i + "", age);
			list1.add(bean);
		}
		JSONArray jsonArray = JSONArray.fromObject(list1);
		System.out.println("list1:" + list1);
		List<ExampleBean> list2 = JSONArray
		                .toList(jsonArray, ExampleBean.class);
		System.out.println("list2:" + list2);
		List<ExampleBean> list3 = JSONArray
        .toList(jsonArray);
		System.out.println("list3:" + list3);
	}
}

  输出结果如下所示:

list1:[ExampleBean@13a328f, ExampleBean@1cd8669, ExampleBean@337838, ExampleBean@119cca4, ExampleBean@ca2dce]
list2:[ExampleBean@765291, ExampleBean@26e431, ExampleBean@14f8dab, ExampleBean@1ddebc3, ExampleBean@a18aa2]
list3:[net.sf.ezmorph.bean.MorphDynaBean@17182c1[
  {id=0, age=20, name=xxlong0}
], net.sf.ezmorph.bean.MorphDynaBean@13f5d07[
  {id=1, age=21, name=xxlong1}
], net.sf.ezmorph.bean.MorphDynaBean@f4a24a[
  {id=2, age=22, name=xxlong2}
], net.sf.ezmorph.bean.MorphDynaBean@cac268[
  {id=3, age=23, name=xxlong3}
], net.sf.ezmorph.bean.MorphDynaBean@1a16869[
  {id=4, age=24, name=xxlong4}
]]

5.通过 Servlet 或 MVC 框架输出 JSON 时，需要设置正确的 MIME 类型（application/json）和字符编码。假定服务器使用 UTF-8 编码，则可以使用以下代码输出编码后的 JSON 文本:

response.setContentType("application/json;charset=UTF-8");
response.setCharacterEncoding("UTF-8");
PrintWriter out = response.getWriter();
out.print(jsonObject);
out.flush();
out.close();

6.在前台处理jsonobject:

var json = {"customerGroupList":
[{"id":{"customerGroupId":1,"languageId":1},"lastModified":null,"name":"medium level","priceId":1},
{"id":{"customerGroupId":2,"languageId":1},"lastModified":null,"name":"medium level2","priceId":1},
{"id":{"customerGroupId":3,"languageId":1},"lastModified":null,"name":"level3","priceId":1}],
"searchResultList":[{"custAddress":"1 Way Street,NeverNever,,PostCode1","custFirstName":"Andy","custLastLogon":"19/01/2010","custLastName":"Admin","custlogons":25},
{"custAddress":"3 Way Street,NeverNever,,PostCode3","custFirstName":"Olly","custLastLogon":"18/12/2009","custLastName":"Order","custlogons":0},
{"custAddress":"1 Way Street,NeverNever,,12345","custFirstName":"John","custLastLogon":"18/12/2009","custLastName":"Doe","custlogons":0},
{"custAddress":"2 Way Street,NeverNever,,PostCode2","custFirstName":"Caty","custLastLogon":"18/12/2009","custLastName":"Catalog","custlogons":0}]};

 这是一个非常复杂的jsonobject对象.在后台,它是将一个个CustomerGroup对象和CustomerSearchResult对象分别存入的ArrayList中,然后再以customerGroupList和searchResultList为key存入HashMap中,最后转化为jsonobject对象传递到前台.在前台进行处理时,你可以把它看成一个变通地js对象,然后使用属性访问来得到它对应的属性值.

如:

//就可以得到一个js数组对象,即json对象的前面一部分.即用[]括隹的那个对象.
var custGroupList = json.customerGroupList;
//同样.它也是得到一个js数组对象
var array2 = json.searchResultList;
for(var i = 0 ; i < array2.length; i++){
    //得到array中的每一个对象
    var cust = array[i];
    var result = "";
//得到每一个对象的属性及属性值,当然也可以使用Object.attributeName.这 种方式得到对象的属性值,根据个人喜好
    for(var attrName in cust){
      result = "attribute name = " + attrName + "and attribute value = "  + cust[attrName];
    }
}

 

再如,你从后以会了一个如下所示的json对象,它在后台其实是一个map对象:

var mapping = {"B202":["B202","B402","B502","B702"],"B201":["B201","B401","B501","B701"],"B103":["B103","B403","B503","B703"],"B703":["B703"]}

 这时,比如你要取得B202的映射,你可以使用期mapping.B202,你得到的结果就是B202相对应的值,即:

["B202","B402","B502","B702"]

这在js中是一个数组,它具有数组具有的一切功能,它在后台中是java的一个list对象.如果你要动态的取值,比如传过来一个id,这个id可以是B202,B201或B103等等,比如,传进来的id=B202,这时,你就不能用mapping.id取值了,这样的话,它会去取mapping这个json对象中id属性这个值,而mapping对象中没有id这个属性,所有返回给你的是一个undefined,你应该使用mapping[id]这种方法来动态取值,这时它就会正确的返回结果:

["B202","B402","B502","B702"]

7.有关boolean值

如果你的Bean中有boolean属性值的话，你要注意boolean属性值的命名，如果你使用is开头，如isSucc，然后又是用eclipse生成它的setter和getter方法时，你就会遇到意想不到麻烦，因为你的setter方法不再是setIsSucc,而是setSucc,所以转化成Bean时它就会有问题

看例子：TestBoolean类代码如下所示：

public class TestBoolean {

	private boolean	isSucc;
	private String	msg;
	
    public TestBoolean() {
	    super();
	    // TODO Auto-generated constructor stub
    }

    public TestBoolean(boolean isSucc, String msg) {
	    super();
	    this.isSucc = isSucc;
	    this.msg = msg;
    }
  
    public boolean isSucc() {
    	return isSucc;
    }

    public void setSucc(boolean isSucc) {
    	this.isSucc = isSucc;
    }

    public String getMsg() {
    	return msg;
    }

    public void setMsg(String msg) {
    	this.msg = msg;
    }
}

注意TestBoolean中属性isSucc的setter方法。

测试方法如下所示：

@Test
	public void test() {
		String json = "{isSucc: true,msg: 'This is msg property!'}";
	    JSONObject jsonObj = JSONObject.fromObject( json ); 
	    TestBoolean bean = (TestBoolean)JSONObject.toBean( jsonObj, TestBoolean.class );
	    System.out.println(bean.isSucc());
	    assertEquals(true, bean.isSucc());
	}

 这时junit测试会通不过，报告一个failure,同进控制台打印出了false. 这是因为TestBoolean这个类属性isSucc的setter方法并不是setIsSucc,而是setIsSucc,所以转化Bean时,它会根据你传入的属性名是isSucc,值是true;所以它会去查询setIsSucc方法给isSucc赋值,它没有找到setIsSucc这个方法,所以就没法给isSucc赋值;如果你将你的json对象改成succ:true;再进行测试,此测试就会成功了,并且控制台打印出了true。如下所示：

String json = "{succ: true,msg: 'This is msg property!'}";

 或者你不修改json字符串，你可以只修改isSucc属性的setter方法，改成setIsSucc,测试程序同样可以运行成功。

你将TestBoolean中的boolean属性改成Boolean，效果将是一样的。如下所示：

public class TestBoolean {

	private Boolean	succ;
	private String	msg;

	public TestBoolean() {
		super();
		// TODO Auto-generated constructor stub
	}

	public TestBoolean(Boolean succ, String msg) {
		super();
		this.succ = succ;
		this.msg = msg;
	}

	public Boolean getSucc() {
		return succ;
	}

	public void setSucc(Boolean succ) {
		this.succ = succ;
	}
......
}

 测试程序还是像上面所示，只是将json字符串修改成

String json = "{succ: true,msg: 'This is msg property!'}";

评论

2 楼 naoda 2010-08-26  

写的很不错，受益匪浅。

1 楼 ihibernate 2010-06-24  

不错