ObjectMapper使用小例子:
首先有個實體對象:
先創建個對象
static ObjectMapper omapper = new ObjectMapper();
一、對象轉換爲json數據
1. User u = new User(); u.setAge(24); u.setUsername("dobble"); omapper.writeValue(new File("D:/aa.txt"), u);//寫到文件中 omapper.writeValue(System.out, u);//輸出到控制檯 輸出:{"username":"dobble","age":24,"list":null,"datetime":null} 2. List<Integer> list=new ArrayList<Integer>(); list.add(1); list.add(2); list.add(3); String result = omapper.writeValueAsString(list);//序列化 System.out.println(result); 輸出:[1,2,3] 3. omapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);<1> DateFormat df = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");<2> omapper.setDateFormat(df); User uu = new User(); uu.setAge(24); uu.setDatetime(new Date()); String[] sts = {"a1","a2","a3"}; uu.setList(sts); uu.setUsername("json"); String r1 = omapper.writeValueAsString(uu); System.out.println(r1); 輸出1:不加時間格式爲-------{"username":"json","age":24,"list":["a1","a2","a3"],"datetime":1463552017876} 加了設置<1>爲--------{"username":"json","age":24,"list":["a1","a2","a3"],"datetime":"2016-05-18T06:26:13.414+0000"} 加了自定義<<2>格式爲-{"username":"json","age":24,"list":["a1","a2","a3"],"datetime":"2016-05-18 02:30:51"} 4. JsonGenerator jg = omapper.getFactory().createGenerator(System.out, JsonEncoding.UTF8); jg.writeObject(uu); //用的是例3的uu對象 System.out.println(); 輸出:加了時間格式---{"username":"json","age":24,"list":["a1","a2","a3"],"datetime":"2016-05-18 02:36:46"}
2.json數據轉換爲對象
File ff = new File("D:/aa.txt"); String str = FileUtils.readFileToString(ff);//可以直接讀文件 文件中爲json數據 // String jsonStr = "{\"username\":\"misty\",\"age\":\"24\"}";//也可以自己寫json數據 User user = omapper.readValue(str, User.class); System.out.println(user.getAge()+"--"+user.getUsername());
輸出爲:24--dobble
獲取複雜json數據的特定數據:
String test="{"results":[
{"objectID":357,"geoPoints":[{"x":504604.59802246094,"y":305569.9150390625}]},
{"objectID":358,"geoPoints":[{"x":504602.2680053711,"y":305554.43603515625}]}
]}";//雙引號要加轉義字符,爲了方便可以放到文件中讀取
String test = FileUtils.readFileToString(new File("D:/aa.txt")); //將上面字符串放到aa.txt中
JsonNode jnode = omapper.readTree(test);
JsonNode node = jnode.get("results");
for(int i=0;i<node.size();i++){
System.out.println(node.get(i).get("objectID"));
JsonNode no= node.get(i).get("geoPoints");
for(int j=0;j<no.size();j++){
double n1 = no.get(j).get("x").doubleValue();
double n2 = no.get(j).get("y").doubleValue();
System.out.println(n1 + "--" + n2);
}
}
輸出爲:357
504604.59802246094--305569.9150390625
358
504602.2680053711--305554.43603515625