Jackson基础

一、所需jar包：

　　jackson-core-x.x.x-rc4.jar、jackson-databind-x.x.x-rc4.jar、jackson-annotations-x.x.x-rc4.jar（本例使用jackson-core-2.6.0-rc4.jar、jackson-databind-2.6.0-rc4.jar、jackson-annotations-2.6.0-rc4.jar）。

二、解析转化：

　　1、json字符串  < ------ >  js

        String str="{\"name\" : \"peter\",\"age\" : 25,\"address\" : \"广州\",\"weight\" : \"55.5\",\"handsome\" : true}";

        //json字符串  ------>  json
        ObjectMapper mapper=new ObjectMapper();
        JsonNode jsonNode=mapper.readTree(str);

        //json  ------>json字符串
        String jsonStr=jsonNode.toString();

　　2、java实体类  < ------ >  json

public class User {
    private String name;
    private int age;
    private String address;
    private double weight;
    private boolean handsome;
    //此处省略构造方法和get、set方法

        User user=new User("peter", 20, "广州", 55.5, true);

        ObjectMapper mapper=new ObjectMapper();
        //java实体类 ------>  json字符串
        String jsonStr=mapper.writeValueAsString(user);
        //json字符串------>json
        JsonNode json=mapper.readTree(jsonStr);

        //json  ------>  java实体类
        User user2=mapper.readValue(jsonStr, User.class);

　　3、List  < ------ >  json

        List<String> list=new ArrayList<String>();
        list.add("QQQQQQ");
        list.add("WWWWWW");
        list.add("EEEEEE");
        list.add("RRRRRR");

        ObjectMapper mapper=new ObjectMapper();
        //List  ------>  json字符串
        String jsonStr=mapper.writeValueAsString(list);
        //json字符串  ------> json
        JsonNode jsonNode=mapper.readTree(jsonStr);
        //json字符串  ------> List
        List<String> list2=mapper.readValue(jsonStr, List.class);

　　4、Map  < ------ >  json

        Map<String, String> map=new HashMap<String, String>();
        map.put("name", "peter");
        map.put("sex", "Man");
        map.put("age", "20");

        ObjectMapper mapper=new ObjectMapper();
        //Map  ------>  json字符串
        String jsonStr=mapper.writeValueAsString(map);
        //json字符串  ------>  json
        JsonNode json=mapper.readTree(jsonStr);
        //json  ------>  Map
        Map<String, String> map2=mapper.readValue(json.toString(), Map.class);

　　5、Set  < ------ >  json

        Set<String> set=new HashSet<String>();
        set.add("QQQQQQ");
        set.add("wwwwww");
        set.add("eeeeee");

        ObjectMapper mapper=new ObjectMapper();
        //Set  ------>  json字符串
        String jsonStr=mapper.writeValueAsString(set);
　　　　 //json字符串  ------> json
　　　　 JsonNode jsonNode=mapper.readTree(jsonStr);
        //json字符串  ------>  Set
        Set<String> set2=mapper.readValue(jsonStr, Set.class);

三、CRUD:

　　1、查询数据：

        //peter
        String name=jsonNode.get("name").asText();
        //"peter"
        String name1=jsonNode.get("name").toString();

        //提取handsome(true)
        JsonNode handsome=jsonNode.path("handsome");

        int age=jsonNode.get("age").asInt();
        double weight=jsonNode.get("weight").asDouble();
        boolean handsome=jsonNode.get("handsome").asBoolean()

        for (int i = 0; i < jsonNode.size(); i++) {
            System.out.println(jsonNode.get(i));
        }

　　2、增加数据：

        ObjectMapper mapper=new ObjectMapper();
        ObjectNode node=mapper.createObjectNode();
        //{"name":"DJ","age":18}
        node.put("name", "DJ");
        node.put("age", 18);
        

        ArrayNode arrayNode=mapper.createArrayNode();
        //["name","age"]
        arrayNode.add("name");
        arrayNode.add("age");

　　3、删除数据：

        ObjectMapper mapper=new ObjectMapper();
        ObjectNode node=mapper.createObjectNode();

        node.put("name", "DJ");
        node.put("age", 18);

        node.remove("name");

        ArrayNode arrayNode=mapper.createArrayNode();
        //["name","age"]
        arrayNode.add("name");
        arrayNode.add("age");
        int index=0;
        arrayNode.remove(index);

　　4、修改数据：

        ObjectMapper mapper=new ObjectMapper();
        ObjectNode node=mapper.createObjectNode();

        node.put("name", "DJ");
        node.put("age", 18);

        //重置数据
        node.put("name", "MDJ");

        ArrayNode arrayNode=mapper.createArrayNode();
        //["name","age"]
        arrayNode.add("name");
        arrayNode.add("age");

        for (int i = 0; i < arrayNode.size(); i++) {
            if("name".equals(arrayNode.get(i).asText())){
                arrayNode.remove(i);
                arrayNode.add("userName");
            }
        }