基于Jackson实现对象的序列化和反序列化工具

import org.apache.commons.lang3.StringUtils;
import org.codehaus.jackson.map.DeserializationConfig;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializationConfig;
import org.codehaus.jackson.map.annotate.JsonSerialize;
import org.codehaus.jackson.type.JavaType;
import org.codehaus.jackson.type.TypeReference;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.List;

// 将对象和Json相互转换
public class JsonUtil {
    private static Logger logger = LoggerFactory.getLogger(JsonUtil.class);
    private static ObjectMapper objectMapper = new ObjectMapper();
    static {
        // 对象的所有字段全部列入
        objectMapper.setSerializationInclusion(JsonSerialize.Inclusion.ALWAYS);
        // 取消默认转换timestamps对象
        objectMapper.configure(SerializationConfig.Feature
                .WRITE_DATE_KEYS_AS_TIMESTAMPS, false);
        // 忽略空Bean转json的错误
        objectMapper.configure(SerializationConfig.Feature
                .FAIL_ON_EMPTY_BEANS, false);
        // 所有日期统一格式
        objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));

        // 忽略 在json字符串中存在, 但是在java对象中不存在对应属性的情况, 防止出错
        objectMapper.configure(DeserializationConfig.Feature
                .FAIL_ON_UNKNOWN_PROPERTIES, false);
    }
    public static <T> String obj2String(T obj) {
        if (obj == null) {
            return null;
        }
        try {
            return obj instanceof String ? (String)obj : objectMapper
                    .writeValueAsString
                    (obj);
        } catch (Exception e) {
            logger.error("Parse object to String error:" + e);
            return null;
        }
    }

    /**
     * 返回一个格式化好的字符串, 用于调试
     * @param obj
     * @param <T>
     * @return
     */
    public static <T> String obj2StringPretty(T obj) {
        if (obj == null) {
            return null;
        }
        try {
            return obj instanceof String ? (String)obj : objectMapper.writerWithDefaultPrettyPrinter()
                    .writeValueAsString
                            (obj);
        } catch (Exception e) {
            logger.error("Parse object to String error:" + e);
            return null;
        }
    }

    /**
     * 将字符串转成对象, 单个
     * @param str
     * @param clazz
     * @param <T>
     * @return
     */
    public static <T> T string2Obj(String str, Class<T> clazz) {
        if (StringUtils.isEmpty(str) || clazz == null) {
            return null;
        }
        try {
            return clazz.equals(String.class) ? (T)str : objectMapper.readValue
                    (str, clazz);
        } catch (IOException e) {
            logger.error("Parse String to Object error :" + e);
            return null;
        }
    }

    /**
     * 将字符串转换成对象, 数组
     * @param str
     * @param typeReference
     * @param <T>
     * @return
     */
    public static <T> T string2Obj(String str, TypeReference<T> typeReference) {
        if (StringUtils.isEmpty(str) || typeReference == null) {
            return null;
        }
        try {
            return (T)(typeReference.getType().equals(String.class) ? (T)str :
                    objectMapper.readValue
                    (str, typeReference));
        } catch (IOException e) {
            logger.error("Parse String to typeReference Object error :" + e);
            return null;
        }
    }
    /**
     * 将字符串转换成对象, 数组
     * @param str
     * @param typeReference
     * @param <T>
     * @return
     */
    public static <T> T string2Obj(String str, Class<?> collectionClass,
                                   Class<?>... elementClasses) {
        JavaType javaType = objectMapper.getTypeFactory()
                .constructParametricType(collectionClass, elementClasses);
        try {
            return objectMapper.readValue(str, javaType);
        } catch (IOException e) {
            logger.error("Parse String to Object2 error :" + e);
            return null;
        }
    }

    /**
     * 测试代码
     */
    public static void main(String[] args) {
        User user1 = new User();
        user1.setId(209);
        user1.setPassword("dhjskhsjdhj");
        user1.setAnswer("ccccccccc");

        User user2 = new User();
        user2.setId(300);
        user2.setPassword("300wwwwww");
        user2.setAnswer("300wwwwwweeeeeeeeee");

        List list = new ArrayList();
        list.add(user1);
        list.add(user2);

        String str = obj2String(list);
        System.out.println("strL:::::" + str);


        List<User> userList = string2Obj(str, new TypeReference<List<User>>()
        {});

        List<User> userList2 = string2Obj(str, List.class, User.class);

        System.out.println("end");


    }
}