JSON工具

package com.hq.schoolcj.util;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonParser.Feature;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import java.io.IOException;
import java.io.StringWriter;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
/**
 * json javabean 之间的转换工具;
 * servlet 输出工具
 *
 * @author yangyang.cong
 */
public abstract class JSONUtil {
    private static final ObjectMapper MAPPER = new ObjectMapper();
    private static final JsonFactory JSONFACTORY =new JsonFactory();
    private static final Gson GSON = new GsonBuilder().create();
    public static<T> String objToGson(T t) {
        return GSON.toJson(t);
    }
    public static<T> T gsonToObj(String gson, Class<T> type) {
        return GSON.fromJson(gson,type);
    }
    /**
     * 转换Java Bean 为 json
     */
    public static String beanToJson(Object o) {
        StringWriter sw = new StringWriter(300);
        JsonGenerator gen = null;
        try {
            gen = JSONFACTORY.createGenerator(sw);
            MAPPER.writeValue(gen, o);
            return sw.toString();
        } catch (Exception e) {
            throw new RuntimeException("JSON转换失败", e);
        } finally {
            if (gen != null) try {
                gen.close();
            } catch (IOException ignored) {
            }
        }
    }
    public static String beanToJson(ToJson o) {
        return o.toJsonString();
    }
    /**
     * 转换Java Bean 为 HashMap
     */
    public static Map<String, Object> beanToMap(Object o) {
        try {
            return (Map) MAPPER.readValue(beanToJson(o), HashMap.class);
        } catch (IOException e) {
            throw new RuntimeException("转换失败", e);
        }
    }
    /**
     * 转换Json String 为 HashMap
     */
    public static Map<String, Object> jsonToMap(String json) {
        try {
            //配置转义字符
            MAPPER.configure(Feature.ALLOW_UNQUOTED_CONTROL_CHARS, true);
            return (Map) MAPPER.readValue(json, HashMap.class);
        } catch (IOException e) {
            System.out.println(e.toString());
            throw new RuntimeException("转换失败", e);
        }
    }
    public static String hashMapToJson(Map<String, String> params) {  
        String dot = "\"";
        String string = "{";  
        for (Iterator it = params.entrySet().iterator(); it.hasNext();) {  
            Entry e = (Entry) it.next();  
            string += dot + e.getKey() + dot+":";  
            string += dot + e.getValue() + dot+",";  
        }  
        string = string.substring(0, string.lastIndexOf(","));  
        string += "}";  
        return string;  
    } 
    /**
     * 转换Json String 为 JavaBean
     */
    public static <T> T jsonToBean(String json, Class<T> type) {
        try {
            return MAPPER.readValue(json, type);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
    static {
        MAPPER.configure(Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
        MAPPER.configure(Feature.ALLOW_SINGLE_QUOTES, true);
        MAPPER.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES,false);
        //MAPPER.getSerializationConfig().withSerializationInclusion(JsonInclude.Include.NON_NULL);
    }
    public static void validateJSON(String json) throws IOException {
        try(JsonParser parser = JSONFACTORY.createParser(json)){
            while (parser.nextToken() != null) {
            }
        }
    }
    public interface ToJson{
        String toJsonString();
    }
}