fastjson和jackson JSON转换实践

客官°小女子只卖身不卖艺 2022-04-11 06:59 238阅读 0赞

在实际开发过程，需将请求第三方返回的JSON串转成JAVA对象，用fastjson发现，如果JAVA对象中缺少JSON串的key，将不能正常转换，将会报报Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "amount"之类的异常。当然可以补全JAVA对象中属性，但毕竟是第三方返回的JSON串，以后第三方如果再增加新的key那也必须同时修改我们的JAVA对象，就强依赖了。于是用jackson工具，发现无此问题。

下面是测试验证的完整代码：

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字符与对像转换
     */
    public final class JacksonUtil {
    
        public static ObjectMapper objectMapper;
    
        /**
         * 使用泛型方法，把json字符串转换为相应的JavaBean对象。
         * (1)转换为普通JavaBean：readValue(json,Student.class)
         * (2)转换为List,如List<Student>,将第二个参数传递为Student
         * [].class.然后使用Arrays.asList();方法把得到的数组转换为特定类型的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数组转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;
            }
        }
    
        /**
         * 把JavaBean转换为json字符串
         * 
         * @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 {
            
            //报Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "amount"异常
            String str = "{\"name\":\"白白\",\"age\":18,\"city\":\"shengzhen\",\"amount\":100,\"total\":\"172cm\"}";
            
            //OK
            //String str = "{\"name\":\"白白\",\"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 {
    
        /**
         * 把json字符串转换为map
         * 
         * @param jsonStr
         * @return
         */
        public static Map<String, Object> json2Map(String jsonStr) {
    
            Map<String, Object> resMap = (Map<String, Object>) JSON.parse(jsonStr);
            return resMap;
        }
        
        /**
         * 把json字符串转换为相应的JavaBean对象
         * 
         * @param jsonStr
         * @param valueType
         * @return
         */
        public static <T> T toObject(String jsonStr, Class<T> valueType) {
            
            return JSON.parseObject(jsonStr, valueType);
        }
        
        /**
        * 把JavaBean转换为json字符串
        * 
        * @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\":\"白白\",\"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());
            }
        }
    }