JsonUtils

桃扇骨 2023-10-16 09:37 24阅读 0赞

### 1、工具类 ###

package com.atguigu.utils;
    
    import com.fasterxml.jackson.annotation.JsonInclude;
    import com.fasterxml.jackson.core.JsonProcessingException;
    import com.fasterxml.jackson.core.type.TypeReference;
    import com.fasterxml.jackson.databind.DeserializationFeature;
    import com.fasterxml.jackson.databind.JavaType;
    import com.fasterxml.jackson.databind.ObjectMapper;
    import com.fasterxml.jackson.databind.SerializationFeature;
    import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
    
    import java.io.IOException;
    import java.text.SimpleDateFormat;
    import java.time.LocalDateTime;
    import java.time.format.DateTimeFormatter;
    import java.util.ArrayList;
    import java.util.List;
    
    import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateTimeDeserializer;
    import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateTimeSerializer;
    import lombok.extern.slf4j.Slf4j;
    import org.apache.commons.lang3.StringUtils;
    
    /**
     * 基于Jackson的JSON转换工具类
     *
     * @author: XuXin
     * @date: 2023/9/18
     */
    @Slf4j
    public class JsonUtils {
        
        // 定义jackson对象
        private static final ObjectMapper objectMapper = new ObjectMapper();
    
        static {
        
            // 对象的所有字段全部列入，还是其他的选项，可以忽略null等
            objectMapper.setSerializationInclusion(JsonInclude.Include.ALWAYS);
            // 设置Date类型的序列化及反序列化格式
            objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
            // 忽略空Bean转json的错误
            objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
            // 忽略未知属性，防止json字符串中存在，java对象中不存在对应属性的情况出现错误
            objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
            // 注册一个时间序列化及反序列化的处理模块，用于解决jdk8中localDateTime等的序列化问题
            objectMapper.registerModule(new JavaTimeModule()
                    .addSerializer(LocalDateTime.class,
                            new LocalDateTimeSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")))
                    .addDeserializer(LocalDateTime.class,
                            new LocalDateTimeDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")))
            );
        }
    
        /**
         * 对象 => json字符串
         *
         * @param obj 源对象
         */
        public static String format(Object obj) {
        
            String json = null;
            if (obj != null) {
        
                try {
        
                    json = objectMapper.writeValueAsString(obj);
                } catch (JsonProcessingException e) {
        
                    log.warn(e.getMessage(), e);
                    throw new IllegalArgumentException(e.getMessage());
                }
            }
            return json;
        }
    
        /**
         * json字符串 => 对象
         *
         * @param jsonStr 源json串
         * @param clazz   对象类
         * @param <T>     泛型
         */
        public static <T> T parse(String jsonStr, Class<T> clazz) {
        
            return parse(jsonStr, clazz, null);
        }
    
        /**
         * json字符串 => 对象
         *
         * @param jsonStr 源json串
         * @param type    对象类型
         * @param <T>     泛型
         */
        public static <T> T parse(String jsonStr, TypeReference<T> type) {
        
            return parse(jsonStr, null, type);
        }
    
        /**
         * json => 对象处理方法
         * <br>
         * 参数clazz和type必须一个为null，另一个不为null
         * <br>
         * 此方法不对外暴露，访问权限为private
         *
         * @param jsonStr 源json串
         * @param clazz   对象类
         * @param type    对象类型
         * @param <T>     泛型
         */
        private static <T> T parse(String jsonStr, Class<T> clazz, TypeReference<T> type) {
        
            T obj = null;
            if (!StringUtils.isEmpty(jsonStr)) {
        
                try {
        
                    if (clazz != null) {
        
                        obj = objectMapper.readValue(jsonStr, clazz);
                    } else {
        
                        obj = objectMapper.readValue(jsonStr, type);
                    }
                } catch (IOException e) {
        
                    log.warn(e.getMessage(), e);
                    throw new IllegalArgumentException(e.getMessage());
                }
            }
            return obj;
        }
    
        public static <T> List<T> json2List(String jsonStr, Class<T> beanType) {
        
            JavaType javaType = objectMapper.getTypeFactory().constructParametricType(ArrayList.class, beanType);
            try {
        
                List<T> list = objectMapper.readValue(jsonStr, javaType);
                return list;
            } catch (Exception e) {
        
                e.printStackTrace();
            }
            return null;
        }
    
    }

### 2、使用 ###

@SpringBootTest
    class MybatisplusApplicationTests {
        
        @Test
        void contextLoads() throws IOException {
        
            User user = new User();
            user.setName("pp");
            user.setAge(17);
            String s = JsonUtils3.format(user);
            User user1 = JsonUtils3.parse(s, User.class);
            User user2 = JsonUtils3.parse(s, new TypeReference<User>() {
        });
            Map<String, String> map = JsonUtils3.parse(s, new TypeReference<Map<String, String>>() {
        });
            String s2 = "[\n" +
                    "{\"id\": 1, \"name\": \"John\"},\n" +
                    "{\"id\": 2, \"name\": \"Jane\"},\n" +
                    "{\"id\": 3, \"name\": \"Bob\"}\n" +
                    "]";
            String s3 = "[{\"id\":null,\"name\":\"pp\",\"age\":17,\"email\":null,\"persion\":null}]";
            List<User> users1 = JsonUtils3.json2List(s2, User.class);
            List<User> users2 = JsonUtils3.json2List(s3, User.class);
        }
    }

s:  
\{“id”:null,“name”:“pp”,“age”:17,“email”:null,“persion”:null\}  
s2:  
\[  
\{“id”: 1, “name”: “John”\},  
\{“id”: 2, “name”: “Jane”\},  
\{“id”: 3, “name”: “Bob”\}  
\]  
s3:  
\[\{“id”:null,“name”:“pp”,“age”:17,“email”:null,“persion”:null\}\]  
![在这里插入图片描述][44479fe32d35461eaa46b5fac10ba8b8.png]

[44479fe32d35461eaa46b5fac10ba8b8.png]: https://img-blog.csdnimg.cn/44479fe32d35461eaa46b5fac10ba8b8.png