Jackson工具类

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 lombok.extern.slf4j.Slf4j;
import org.springframework.util.StringUtils;

import java.io.IOException;
import java.text.SimpleDateFormat;

@Slf4j
public class JacksonUtil {

    public final static ObjectMapper mapper = new ObjectMapper();
    // 日期格式化
    private static final String STANDARD_FORMAT = "yyyy-MM--dd HH:mm:ss";

    static {
        // 取消默认的timestamp转换
        mapper.configure(SerializationFeature.WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS, false);
        // 忽略空bean转json的错误
        mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
        // 设置日期格式
        mapper.setDateFormat(new SimpleDateFormat(STANDARD_FORMAT));
        // 忽略json中存在,但java对象中不存在对应属性的情况
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

    }

    /**
     * Object转字符串
     *
     * @param obj
     * @param <T>
     * @return
     */
    public static <T> String object2String(T obj) {
        if (obj == null) {
            return null;
        }
        try {
            return obj instanceof String ? (String) obj : mapper.writeValueAsString(obj);
        } catch (JsonProcessingException e) {
            log.warn("Parse Object to String error: {}", e.getMessage());
            return null;
        }
    }

    /**
     * 转美化的 格式化的Json字符串
     *
     * @param obj
     * @param <T>
     * @return
     */
    public static <T> String object2StringPretty(T obj) {
        if (obj == null) {
            return null;
        }
        try {
            return obj instanceof String ? (String) obj : mapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj);
        } catch (JsonProcessingException e) {
            log.warn("Parse Object to String error: {}", e.getMessage());
            return null;
        }
    }

    /**
     * json转java对象
     *
     * @param json
     * @param clazz
     * @param <T>
     * @return
     */
    public static <T> T string2Object(String json, Class<T> clazz) {
        if (StringUtils.isEmpty(json) || clazz == null) {
            return null;
        }
        try {
            return String.class.equals(clazz) ? (T) json : mapper.readValue(json, clazz);
        } catch (IOException e) {
            log.warn("Parse String to Object error: {}", e.getMessage());
            return null;
        }
    }

    /**
     * json转集合类型
     *
     * @param json
     * @param collectionClazz
     * @param elementClazz
     * @param <T>
     * @return
     */
    public static <T> T string2Object(String json, Class<?> collectionClazz, Class<?> elementClazz) {
        if (StringUtils.isEmpty(json) || collectionClazz == null || elementClazz == null) {
            return null;
        }
        JavaType javaType = mapper.getTypeFactory().constructParametricType(collectionClazz, elementClazz);
        try {
            return mapper.readValue(json, javaType);
        } catch (IOException e) {
            log.warn("Parse String to Object error: {}", e.getMessage());
            return null;
        }
    }

    /**
     * json转java对象
     * 可以转集合类型,如 string2Object(json, new TypeReference<List<User>>() {})
     *
     * @param json
     * @param typeReference
     * @param <T>
     * @return
     */
    public static <T> T string2Object(String json, TypeReference<T> typeReference) {
        if (StringUtils.isEmpty(json) || typeReference == null) {
            return null;
        }
        try {
            return typeReference.getType().equals(String.class) ? (T) json : mapper.readValue(json, typeReference);
        } catch (IOException e) {
            log.warn("Parse String to Object error: {}", e.getMessage());
            return null;
        }
    }
}