JSON 的几种转换

package com.qbskj.project.util;

import java.io.IOException;
import java.io.Writer;

import org.springframework.util.Assert;

import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

/**
 * Utils - JSON
 */
public final class JsonUtils {

    /** ObjectMapper */
    private static ObjectMapper mapper = new ObjectMapper();

    /**
     * 不可实例化
     */
    private JsonUtils() {
    }

    /**
     * 将对象转换为JSON字符串
     * 
     * @param value
     *            对象
     * @return JSOn字符串
     */
    public static String toJson(Object value) {
        try {
            return mapper.writeValueAsString(value);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 将JSON字符串转换为对象
     * 
     * @param json
     *            JSON字符串
     * @param valueType
     *            对象类型
     * @return 对象
     */
    public static <T> T toObject(String json, Class<T> valueType) {
        Assert.hasText(json, "");
        Assert.notNull(valueType, "");
        try {
            return mapper.readValue(json, valueType);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 将JSON字符串转换为对象
     * 
     * @param json
     *            JSON字符串
     * @param typeReference
     *            对象类型
     * @return 对象
     */
    public static <T> T toObject(String json, TypeReference<?> typeReference) {
        Assert.hasText(json, "");
        Assert.notNull(typeReference, "");
        try {
            return mapper.readValue(json, typeReference);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 将JSON字符串转换为对象
     * 
     * @param json
     *            JSON字符串
     * @param javaType
     *            对象类型
     * @return 对象
     */
    public static <T> T toObject(String json, JavaType javaType) {
        Assert.hasText(json, "");
        Assert.notNull(javaType, "");
        try {
            return mapper.readValue(json, javaType);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 将对象转换为JSON流
     * 
     * @param writer
     *            writer
     * @param value
     *            对象
     */
    public static void writeValue(Writer writer, Object value) {
        try {
            mapper.writeValue(writer, value);
        } catch (JsonGenerationException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}