Json 在 JAVA 運用範例

Example 1-1 - Encode a JSON objectMapping Between JSON and Java Entities for more information.

//import org.json.simple.JSONObject;

JSONObject obj=new JSONObject();
obj.put("name","foo");
obj.put("num",new Integer(100));
obj.put("balance",new Double(1000.21));
obj.put("is_vip",new Boolean(true));
obj.put("nickname",null);
System.out.print(obj);

Result: {"balance":1000.21,"num":100,"nickname":null,"is_vip":true,"name":"foo"}

Example 1-2 - Encode a JSON object - StreamingMapping Between JSON and Java Entities for more information.

//import org.json.simple.JSONObject;

JSONObject obj=new JSONObject();
obj.put("name","foo");
obj.put("num",new Integer(100));
obj.put("balance",new Double(1000.21));
obj.put("is_vip",new Boolean(true));
obj.put("nickname",null);
StringWriter out = new StringWriter();
obj.writeJSONString(out);
String jsonText = out.toString();
System.out.print(jsonText);

Result: {"balance":1000.21,"num":100,"nickname":null,"is_vip":true,"name":"foo"}


Example 1-3 - Encode a JSON object - Using MapMapping Between JSON and Java Entities for more information.

//import java.util.LinkedHashMap;
//import java.util.Map;
//import org.json.simple.JSONValue;

Map obj=new LinkedHashMap();
obj.put("name","foo");
obj.put("num",new Integer(100));
obj.put("balance",new Double(1000.21));
obj.put("is_vip",new Boolean(true));
obj.put("nickname",null);
String jsonText = JSONValue.toJSONString(obj);
System.out.print(jsonText);

Result: {"name":"foo","num":100,"balance":1000.21,"is_vip":true,"nickname":null}

Example 1-4 - Encode a JSON object - Using Map and streamingMapping Between JSON and Java Entities for more information.

//import java.util.LinkedHashMap;
//import java.util.Map;
//import org.json.simple.JSONValue;

Map obj=new LinkedHashMap();
obj.put("name","foo");
obj.put("num",new Integer(100));
obj.put("balance",new Double(1000.21));
obj.put("is_vip",new Boolean(true));
obj.put("nickname",null);
StringWriter out = new StringWriter();
JSONValue.writeJSONString(obj, out);
String jsonText = out.toString();
System.out.print(jsonText);

Result: {"name":"foo","num":100,"balance":1000.21,"is_vip":true,"nickname":null}

Example 2-1 - Encode a JSON arrayExample 2-2 - Encode a JSON array - StreamingMapping Between JSON and Java Entities for more information.

//import org.json.simple.JSONArray;

JSONArray list = new JSONArray();
list.add("foo");
list.add(new Integer(100));
list.add(new Double(1000.21));
list.add(new Boolean(true));
list.add(null);
System.out.print(list);

   Result: ["foo",100,1000.21,true,null]

//import org.json.simple.JSONArray;

JSONArray list = new JSONArray();
list.add("foo");
list.add(new Integer(100));
list.add(new Double(1000.21));
list.add(new Boolean(true));
list.add(null);
StringWriter out = new StringWriter();
list.writeJSONString(out);
String jsonText = out.toString();
System.out.print(jsonText);

Result: ["foo",100,1000.21,true,null]

Example 2-3 - Encode a JSON array - Using ListMapping Between JSON and Java Entities for more information.

//import org.json.simple.JSONValue;

LinkedList list = new LinkedList();
list.add("foo");
list.add(new Integer(100));
list.add(new Double(1000.21));
list.add(new Boolean(true));
list.add(null);
String jsonText = JSONValue.toJSONString(list);
System.out.print(jsonText);

Result: ["foo",100,1000.21,true,null]

Example 2-4 - Encode a JSON array - Using List and streamingMapping Between JSON and Java Entities for more information.

//import org.json.simple.JSONValue;

LinkedList list = new LinkedList();
list.add("foo");
list.add(new Integer(100));
list.add(new Double(1000.21));
list.add(new Boolean(true));
list.add(null);
StringWriter out = new StringWriter();
JSONValue.writeJSONString(list, out);
String jsonText = out.toString();
System.out.print(jsonText);

Result: ["foo",100,1000.21,true,null]

//import org.json.simple.JSONObject;

JSONObject obj1 = new JSONObject();
obj1.put("name","foo");
obj1.put("num",new Integer(100));
obj1.put("balance",new Double(1000.21));
         
JSONObject obj2 = new JSONObject();
obj2.put("is_vip",new Boolean(true));
obj2.put("nickname",null);
obj2.putAll(obj1);
System.out.print(obj2);

Result: {"balance":1000.21,"num":100,"nickname":null,"is_vip":true,"name":"foo"}, the same as the one of Example 1.

JSONArray list1 = new JSONArray();
list1.add("foo");
list1.add(new Integer(100));
list1.add(new Double(1000.21));

JSONArray list2 = new JSONArray();
list2.add(new Boolean(true));
list2.add(null);
list2.addAll(list1);
System.out.print(list2);

Result: [true,null,"foo",100,1000.21], the order of which is different from the one of Example 2.

JSONArray list1 = new JSONArray();
list1.add("foo");
list1.add(new Integer(100));
list1.add(new Double(1000.21));

JSONArray list2 = new JSONArray();
list2.add(new Boolean(true));
list2.add(null);
         
JSONObject obj = new JSONObject();
obj.put("name","foo");
obj.put("num",new Integer(100));
obj.put("balance",new Double(1000.21));
obj.put("is_vip",new Boolean(true));
obj.put("nickname",null);

obj.put("list1", list1);
obj.put("list2", list2);
         
System.out.println(obj);

Result: {"balance":1000.21,"list2":true,null,"num":100,"list1":["foo",100,1000.21],"nickname":null,"is_vip":true,"name":"foo"}

Map m1 = new LinkedHashMap();
Map m2 = new HashMap();
List  l1 = new LinkedList();

m1.put("k11","v11");
m1.put("k12","v12");
m1.put("k13", "v13");
m2.put("k21","v21");
m2.put("k22","v22");
m2.put("k23","v23");
l1.add(m1);
l1.add(m2);

String jsonString = JSONValue.toJSONString(l1);
         
System.out.println(jsonString);

Result: [{"k11":"v11","k12":"v12","k13":"v13"},{"k22":"v22","k21":"v21","k23":"v23"}]

StringWriter out = new StringWriter();
 
JSONObject obj = new JSONObject();
LinkedHashMap m1 = new LinkedHashMap();
LinkedList l1 = new LinkedList();
obj.put("k1", "v1");
obj.put("k2", m1);
obj.put("k3", l1);
m1.put("mk1", "mv1");
l1.add("lv1");
l1.add("lv2");
m1.put("mk2", l1);
 
obj.writeJSONString(out);
System.out.println("jsonString:");
System.out.println(out.toString());
String jsonString = obj.toJSONString();
System.out.println(jsonString);

Result:

jsonString:
{"k3":["lv1","lv2"],"k1":"v1","k2":{"mk1":"mv1","mk2":["lv1","lv2"]}}
{"k3":["lv1","lv2"],"k1":"v1","k2":{"mk1":"mv1","mk2":["lv1","lv2"]}}

/*class User implements JSONAware{
    private int id;
    private String name;
    private String password;
 
    public User(int id, String name, String password){
            this.id = id;
            this.name = name;
            this.password = password;
    }
 
    public String toJSONString(){
            StringBuffer sb = new StringBuffer();
         
            sb.append("{");
         
            sb.append(JSONObject.escape("userName"));
            sb.append(":");
            sb.append("\"" + JSONObject.escape(name) + "\"");
         
            sb.append(",");
         
            sb.append(JSONObject.escape("ID"));
            sb.append(":");
            sb.append(id);
         
            sb.append("}");
         
            return sb.toString();
    }
}*/


JSONArray users = new JSONArray();
users.add(new User(123,"foo1", "secret1"));
users.add(new User(124,"foo2", "secret2"));
users.add(new User(125,"\"foo2\"", "secret2"));
System.out.println(users);

Result: [{userName:"foo1",ID:123},{userName:"foo2",ID:124},{userName:"\"foo2\"",ID:125}]

User.toJSONString() seems to be a bit complicated. The purpose is to demonstrate the usage of JSONObject.escape(). It can be simpler:

  public String toJSONString(){
    JSONObject obj = new JSONObject();
    obj.put("userName", name);
    obj.put("ID", new Integer(id));
    return obj.toString();
  }

/*class User implements JSONStreamAware{
    private int id;
    private String name;
    private String password;
 
    public User(int id, String name, String password){
            this.id = id;
            this.name = name;
            this.password = password;
    }
 
   public void writeJSONString (Writer out) throws IOException{
            LinkedHashMap obj = new LinkedHashMap();
            obj.put("userName", name);
            obj.put("ID", new Integer(id));
            JSONValue.writeJSONString(obj, out);
   }
}*/

JSONArray users = new JSONArray();
users.add(new User(123,"foo1", "secret1"));
users.add(new User(124,"foo2", "secret2"));
users.add(new User(125,"\"foo2\"", "secret2"));
StringWriter out = new StringWriter();
users.writeJSONString(out);
System.out.println(out.toString());

Result: [{"userName":"foo1","ID":123},{"userName":"foo2","ID":124},{"userName":"\"foo2\"","ID":125}]

出處