JSON与JAVA数据的转换

最新推荐文章于 2024-07-08 02:53:14 发布

VooleBoy

最新推荐文章于 2024-07-08 02:53:14 发布

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分类专栏： java 文章标签： json Java Bean .net XML

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本文详细介绍JSON-lib库的使用方法，包括基本数据类型如List、Map、Bean等转换为JSON及从JSON转换回来的过程，并提供了常见问题解决方案。

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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。

下载地址:http://json-lib.sourceforge.net/
还要需要的第3方包:
org.apache.commons(3.2以上版本)
org.apache.oro
net.sf.ezmorph(ezmorph-1.0.4.jar)
nu.xom

1、List

Java代码

boolean [] boolArray = new boolean []{ true , false , true };
JSONArray jsonArray1 = JSONArray.fromObject( boolArray );
System.out.println( jsonArray1 );
// prints [true,false,true]
List list = new ArrayList();
list.add( "first" );
list.add( "second" );
JSONArray jsonArray2 = JSONArray.fromObject( list );
System.out.println( jsonArray2 );
// prints ["first","second"]
JSONArray jsonArray3 = JSONArray.fromObject( "['json','is','easy']" );
System.out.println( jsonArray3 );
// prints ["json","is","easy"]

boolean[] boolArray = new boolean[]{true,false,true};
JSONArray jsonArray1 = JSONArray.fromObject( boolArray );
System.out.println( jsonArray1 );
// prints [true,false,true]
List list = new ArrayList();
list.add( "first" );
list.add( "second" );
JSONArray jsonArray2 = JSONArray.fromObject( list );
System.out.println( jsonArray2 );
// prints ["first","second"]
JSONArray jsonArray3 = JSONArray.fromObject( "['json','is','easy']" );
System.out.println( jsonArray3 );
// prints ["json","is","easy"]

2、Map

Java代码

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

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

3、BEAN

Java代码

/**
* Bean.java
private String name = "json";
private int pojoId = 1;
private char[] options = new char[]{'a','f'};
private String func1 = "function(i){ return this.options[i]; }";
private JSONFunction func2 = new JSONFunction(new String[]{"i"},"return this.options[i];");
*/
JSONObject jsonObject = JSONObject.fromObject( new JsonBean() );
System.out.println( jsonObject );
//{"func1":function(i){ return this.options[i]; },"pojoId":1,"name":"json","options":["a","f"],"func2":function(i){ return this.options[i]; }}

/**
* Bean.java
private String name = "json";
private int pojoId = 1;
private char[] options = new char[]{'a','f'};
private String func1 = "function(i){ return this.options[i]; }";
private JSONFunction func2 = new JSONFunction(new String[]{"i"},"return this.options[i];");
*/
JSONObject jsonObject = JSONObject.fromObject( new JsonBean() );
System.out.println( jsonObject );
//{"func1":function(i){ return this.options[i]; },"pojoId":1,"name":"json","options":["a","f"],"func2":function(i){ return this.options[i]; }}

4、BEANS

Java代码

/**
* private int row ;
private int col ;
private String value ;
*
*/
List list = new ArrayList();
JsonBean2 jb1 = new JsonBean2();
jb1.setCol( 1 );
jb1.setRow( 1 );
jb1.setValue( "xx" );
JsonBean2 jb2 = new JsonBean2();
jb2.setCol( 2 );
jb2.setRow( 2 );
jb2.setValue( "" );
list.add(jb1);
list.add(jb2);
JSONArray ja = JSONArray.fromObject(list);
System.out.println( ja.toString() );
//[{"value":"xx","row":1,"col":1},{"value":"","row":2,"col":2}]

/**
* private int row ;
private int col ;
private String value ;
*
*/
List list = new ArrayList();
JsonBean2 jb1 = new JsonBean2();
jb1.setCol(1);
jb1.setRow(1);
jb1.setValue("xx");
JsonBean2 jb2 = new JsonBean2();
jb2.setCol(2);
jb2.setRow(2);
jb2.setValue("");
list.add(jb1);
list.add(jb2);
JSONArray ja = JSONArray.fromObject(list);
System.out.println( ja.toString() );
//[{"value":"xx","row":1,"col":1},{"value":"","row":2,"col":2}]

5、String to bean

Java代码

String json = "{name=\"json\",bool:true,int:1,double:2.2,func:function(a){ return a; },array:[1,2]}" ;
JSONObject jsonObject = JSONObject.fromString(json);
Object bean = JSONObject.toBean( jsonObject );
assertEquals( jsonObject.get( "name" ), PropertyUtils.getProperty( bean, "name" ) );
assertEquals( jsonObject.get( "bool" ), PropertyUtils.getProperty( bean, "bool" ) );
assertEquals( jsonObject.get( "int" ), PropertyUtils.getProperty( bean, "int" ) );
assertEquals( jsonObject.get( "double" ), PropertyUtils.getProperty( bean, "double" ) );
assertEquals( jsonObject.get( "func" ), PropertyUtils.getProperty( bean, "func" ) );
List expected = JSONArray.toList( jsonObject.getJSONArray( "array" ) );
assertEquals( expected, (List) PropertyUtils.getProperty( bean, "array" ) );

String json = "{name=\"json\",bool:true,int:1,double:2.2,func:function(a){ return a; },array:[1,2]}";
JSONObject jsonObject = JSONObject.fromString(json);
Object bean = JSONObject.toBean( jsonObject );
assertEquals( jsonObject.get( "name" ), PropertyUtils.getProperty( bean, "name" ) );
assertEquals( jsonObject.get( "bool" ), PropertyUtils.getProperty( bean, "bool" ) );
assertEquals( jsonObject.get( "int" ), PropertyUtils.getProperty( bean, "int" ) );
assertEquals( jsonObject.get( "double" ), PropertyUtils.getProperty( bean, "double" ) );
assertEquals( jsonObject.get( "func" ), PropertyUtils.getProperty( bean, "func" ) );
List expected = JSONArray.toList( jsonObject.getJSONArray( "array" ) );
assertEquals( expected, (List) PropertyUtils.getProperty( bean, "array" ) );

Java代码

String json = "{\"value\":\"xx\",\"row\":1,\"col\":1}" ;
JSONObject jsonObject = JSONObject.fromString(json);
JsonBean2 bean = (JsonBean2) JSONObject.toBean( jsonObject, JsonBean2. class );
assertEquals( jsonObject.get( "col" ), new Integer( bean.getCol()) );
assertEquals( jsonObject.get( "row" ), new Integer( bean.getRow() ) );
assertEquals( jsonObject.get( "value" ), bean.getValue() );

String json = "{\"value\":\"xx\",\"row\":1,\"col\":1}";
JSONObject jsonObject = JSONObject.fromString(json);
JsonBean2 bean = (JsonBean2) JSONObject.toBean( jsonObject, JsonBean2.class );
assertEquals( jsonObject.get( "col" ),new Integer( bean.getCol())  );
assertEquals( jsonObject.get( "row" ), new Integer( bean.getRow() ) );
assertEquals( jsonObject.get( "value" ), bean.getValue() );

6 json to xml
1)
JSONObject json = new JSONObject( true );
String xml = XMLSerializer.write( json );

<o class="object" null="true">

2)
JSONObject json = JSONObject.fromObject("{\"name\":\"json\",\"bool\":true,\"int\":1}");
String xml = XMLSerializer.write( json );
<o class="object">
<name type="string">json</name>
<bool type="boolean">true</bool>
<int type="number">1</int>
</o>
<o class="object">
<name type="string">json</name>
<bool type="boolean">true</bool>
<int type="number">1</int>
</o>
3)
JSONArray json = JSONArray.fromObject("[1,2,3]");
String xml = XMLSerializer.write( json );
<a class="array">
<e type="number">1</e>
<e type="number">2</e>
<e type="number">3</e>
</a>

7 、xml to json
<a class="array">
<e type="function" params="i,j">
return matrix[i][j];
</e>
</a>
<a class="array">
<e type="function" params="i,j">
return matrix[i][j];
</e>
</a>

JSONArray json = (JSONArray) XMLSerializer.read( xml );
System.out.println( json );
// prints [function(i,j){ return matrix[i][j]; }]

如果需要解析的数据间存在级联关系，而互相嵌套引用，在hibernate中极容易嵌套而抛出net.sf.json.JSONException: There is a cycle in the hierarchy异常。

解决办法

1.设置JSON-LIB让其过滤掉引起循环的字段。

Java代码

JsonConfig config = new JsonConfig();
config.setIgnoreDefaultExcludes( false );
config.setCycleDetectionStrategy(CycleDetectionStrategy.LENIENT);
config.registerJsonValueProcessor(Date. class , new DateJsonValueProcessor( "yyyy-MM-dd" )); //date processor register
config.setExcludes( new String[]{ //只要设置这个数组，指定过滤哪些字段。
"consignee" ,
"contract" ,
"coalInfo" ,
"coalType" ,
"startStation" ,
"balanceMan" ,
"endStation"
});
String tempStr = "{\"TotalRecords\":" + total.toString() + ",\"Datas\":" +JSONSerializer.toJSON(list,config).toString()+ "}" ;
out.print(tempStr);

  JsonConfig config = new JsonConfig();
  config.setIgnoreDefaultExcludes(false);   
  config.setCycleDetectionStrategy(CycleDetectionStrategy.LENIENT); 
  config.registerJsonValueProcessor(Date.class,new DateJsonValueProcessor("yyyy-MM-dd")); //date processor register
  config.setExcludes(new String[]{//只要设置这个数组，指定过滤哪些字段。
    "consignee",
    "contract",
    "coalInfo",
    "coalType",
    "startStation",
    "balanceMan",
    "endStation"
  });
  String tempStr = "{\"TotalRecords\":"+ total.toString() +",\"Datas\":"+JSONSerializer.toJSON(list,config).toString()+"}";
  out.print(tempStr);

2.设置JSON-LIB的setCycleDetectionStrategy属性让其自己处理循环，省事但是数据过于复杂的话会引起数据溢出或者效率低下。

Java代码

JsonConfig config = new JsonConfig();
config.setIgnoreDefaultExcludes( false );
config.setCycleDetectionStrategy(CycleDetectionStrategy.LENIENT);
config.registerJsonValueProcessor(Date. class , new DateJsonValueProcessor( "yyyy-MM-dd" )); //date processor register
String tempStr = "{\"TotalRecords\":" + total.toString() + ",\"Datas\":" +JSONSerializer.toJSON(list,config).toString()+ "}" ;
out.print(tempStr);

json-lib-2.2可以为对应的class注册解析类，记住一定要2.2，2.1有同步问题。切记切记。
写一个DateJsonValueProcessor.java

Java代码

package anni.core.web.json;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import net.sf.json.JSONObject;
import net.sf.json.JsonConfig;
import net.sf.json.processors.JsonValueProcessor;
/**
* @author Lingo
* @since 2007-08-02
*/
public class DateJsonValueProcessor implements JsonValueProcessor {
public static final String DEFAULT_DATE_PATTERN = "yyyy-MM-dd" ;
private DateFormat dateFormat;
/**
* 构造方法.
*
* @param datePattern 日期格式
*/
public DateJsonValueProcessor(String datePattern) {
try {
dateFormat = new SimpleDateFormat(datePattern);
} catch (Exception ex) {
dateFormat = new SimpleDateFormat(DEFAULT_DATE_PATTERN);
}
}
public Object processArrayValue(Object value, JsonConfig jsonConfig) {
return process(value);
}
public Object processObjectValue(String key, Object value,
JsonConfig jsonConfig) {
return process(value);
}
private Object process(Object value) {
return dateFormat.format((Date) value);
}
}

package anni.core.web.json;

import java.text.DateFormat;
import java.text.SimpleDateFormat;

import java.util.Date;

import net.sf.json.JSONObject;
import net.sf.json.JsonConfig;
import net.sf.json.processors.JsonValueProcessor;


/**
 * @author Lingo
 * @since 2007-08-02
 */
public class DateJsonValueProcessor implements JsonValueProcessor {
    public static final String DEFAULT_DATE_PATTERN = "yyyy-MM-dd";
    private DateFormat dateFormat;

    /**
     * 构造方法.
     *
     * @param datePattern 日期格式
     */
    public DateJsonValueProcessor(String datePattern) {
        try {
            dateFormat = new SimpleDateFormat(datePattern);
        } catch (Exception ex) {
            dateFormat = new SimpleDateFormat(DEFAULT_DATE_PATTERN);
        }
    }

    public Object processArrayValue(Object value, JsonConfig jsonConfig) {
        return process(value);
    }

    public Object processObjectValue(String key, Object value,
        JsonConfig jsonConfig) {
        return process(value);
    }

    private Object process(Object value) {
        return dateFormat.format((Date) value);
    }
}

然后在bean -> json的时候

Java代码