序列化工具 专门用来处理一些需要序列化的对象

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.core.JsonProcessingException;
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 org.apache.commons.lang3.StringUtils;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.io.IOException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.HashMap;

/**
 * jackson 序列化列。
 */
@Component
public class JsonUtils implements InitializingBean {

    @Autowired
    private ObjectMapper jacksonObjectMapper;

    public static final String DEFAULT_DATE_FORMAT = "yyyy-MM-dd HH:mm:ss";
    private static org.slf4j.Logger logger = LoggerFactory.getLogger(JsonUtils.class);
    private static final DateFormat defalultSdf = new SimpleDateFormat(DEFAULT_DATE_FORMAT);

    private static ObjectMapper objectMapper;

    static {
        objectMapper = new ObjectMapper();
        objectMapper.setDateFormat(defalultSdf);
        objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
        objectMapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    }


    public static ObjectMapper getObjectMapper() {
        return objectMapper;
    }


    public static JavaType getHashMapType(Class<?> keyCls, Class<?> valCls) {
        return objectMapper.getTypeFactory().constructParametricType(HashMap.class, keyCls, valCls);
    }

    public static JavaType getCollectionType(Class<?> collectionClass, Class<?>... elementClasses) {
        return objectMapper.getTypeFactory().constructParametricType(collectionClass, elementClasses);
    }

    /**
     * 序列化为一个Map
     *
     * @param src    String文本
     * @param keyCls Map key 类型。
     * @param valCls Map Value 类型。
     * @param <T>
     * @return
     */
    public static <T> T fromStringAsMap(String src, Class<?> keyCls, Class<?> valCls) {
        JavaType javaType = getHashMapType(keyCls, valCls);
        return fromString(src, javaType);
    }

    /**
     * 序列化一个泛型List
     *
     * @param src    String文本
     * @param valCls List value 类型。
     */
    public static <T> T fromStringAsList(String src, Class<?> valCls) {
        JavaType javaType = getCollectionType(ArrayList.class, valCls);
        return fromString(src, javaType);
    }

    public static <T> T fromString(String src, JavaType t) {

        if (StringUtils.isBlank(src)) {
            return null;
        }

        try {
            return objectMapper.readValue(src, t);
        } catch (IOException e) {
            logger.error("parse json err . ", e.getMessage());
        }

        return null;
    }

    public static <T> T fromString(String src, Class<T> t) {

        if (StringUtils.isBlank(src)) {
            return null;
        }

        try {

            T object = objectMapper.readValue(src, t);
            return object;

        } catch (IOException e) {
            logger.error("write json err . ", e.getMessage());
        }

        return null;
    }


    public static <T> String toString(T t) {

        if (t == null) {
            return "";
        }

        try {
            return objectMapper.writeValueAsString(t);
        } catch (JsonProcessingException e) {
            logger.error("write json err . ", e.getMessage());
        }

        return "";
    }

    @Override
    public void afterPropertiesSet() {
        //spring 配置覆盖默认
        objectMapper = jacksonObjectMapper;

    }
}