fastjsonとjackson JSON変換実践

実際の開発過程では、第三者に返却を要求するJSON列をJAVAオブジェクトに変換する必要があり、fastjsonで発見し、JAVAオブジェクトにJSON列のkeyが欠けていると、正常に変換できなくなり、Exception in thread「main」comに報告する.fasterxml.jackson.databind.Excc.UnrecognizedPropertyException:Unrecognized field「amount」などの異常.もちろんJAVAオブジェクトの中の属性を補完することができますが、結局第三者が返したJSON列なので、後で第三者が新しいkeyを追加すれば、私たちのJAVAオブジェクトを同時に修正しなければならないので、強く依存します.そこでjacksonツールを使って、この問題がないことを発見しました.
次は、テスト検証の完全なコードです.
UserDTO.java

package com.bijian.test;

public class UserDTO {

    private String name;
    private int age;
    private String city;
    private String grade;
    
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getCity() {
        return city;
    }
    public void setCity(String city) {
        this.city = city;
    }
    public String getGrade() {
        return grade;
    }
    public void setGrade(String grade) {
        this.grade = grade;
    }
    
    @Override
    public String toString() {
        return "UserDTO [name=" + name + ", age=" + age + ", city=" + city + ", grade=" + grade + "]";
    }
}

JacksonUtil.java

package com.bijian.test;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

/**
 * json       
 */
public final class JacksonUtil {

    public static ObjectMapper objectMapper;

    /**
     *       ， json         JavaBean  。
     * (1)     JavaBean：readValue(json,Student.class)
     * (2)   List, List<Student>,         Student
     * [].class.    Arrays.asList();                List
     * 
     * @param jsonStr
     * @param valueType
     * @return
     * @throws Exception 
     */
    public static <T> T readValue(String jsonStr, Class<T> valueType) throws Exception {
        
        if (objectMapper == null) {
            objectMapper = new ObjectMapper();
        }

        try {
            return objectMapper.readValue(jsonStr, valueType);
        } catch (Exception e) {
            throw e;
        }
    }

    /**
     * json   List
     * @param jsonStr
     * @param valueTypeRef
     * @return
     * @throws Exception 
     */
    public static <T> T readValue(String jsonStr, TypeReference<T> valueTypeRef) throws Exception {
        if (objectMapper == null) {
            objectMapper = new ObjectMapper();
        }

        try {
            return objectMapper.readValue(jsonStr, valueTypeRef);
        } catch (Exception e) {
            throw e;
        }
    }

    /**
     *  JavaBean   json   
     * 
     * @param object
     * @return
     * @throws Exception 
     */
    public static String toJson(Object object) throws Exception {
        
        if (objectMapper == null) {
            objectMapper = new ObjectMapper();
        }

        try {
            return objectMapper.writeValueAsString(object);
        } catch (Exception e) {
            throw e;
        }
    }
    
    public static void main(String[] args) throws Exception {
        
        // Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "amount"  
        String str = "{\"name\":\"  \",\"age\":18,\"city\":\"shengzhen\",\"amount\":100,\"total\":\"172cm\"}";
        
        //OK
        //String str = "{\"name\":\"  \",\"age\":18,\"city\":\"shengzhen\"}";
        UserDTO userDTO = JacksonUtil.readValue(str, UserDTO.class);
        System.out.println(userDTO);
    }
}

FastJsonUtil.java

package com.bijian.test;

import java.util.Map;
import java.util.Map.Entry;

import com.alibaba.fastjson.JSON;

public class FastJsonUtil {

    /**
     *  json      map
     * 
     * @param jsonStr
     * @return
     */
    public static Map<String, Object> json2Map(String jsonStr) {

        Map<String, Object> resMap = (Map<String, Object>) JSON.parse(jsonStr);
        return resMap;
    }
    
    /**
     *  json         JavaBean  
     * 
     * @param jsonStr
     * @param valueType
     * @return
     */
    public static <T> T toObject(String jsonStr, Class<T> valueType) {
        
        return JSON.parseObject(jsonStr, valueType);
    }
    
    /**
    *  JavaBean   json   
    * 
    * @param object
    * @return
    * @throws Exception 
    */
    public static String toJson(Object object) {

        return JSON.toJSONString(object);
    }
    
    public static void main(String[] args) throws Exception {
        
        String str = "{\"name\":\"  \",\"age\":18,\"city\":\"shengzhen\",\"amount\":100,\"total\":\"172cm\"}";
        UserDTO userDTO = FastJsonUtil.toObject(str, UserDTO.class);
        System.out.println(userDTO);
        
        
        Map<String, Object> resMap = FastJsonUtil.json2Map(str);
        for(Entry<String, Object> entry : resMap.entrySet()) {
            System.out.println(entry.getKey() + ":" + entry.getValue());
        }
    }
}