gson ajax 數字精度丟失

ajax傳輸的json，gson會發生丟失，long > 15的時候會丟失0

解決方案：直接把屬性爲long的屬性自動加上雙引號成爲js的字符串，這樣就不會發生丟失了，ajax自動識別爲字符串。

用法:

ajaxResult("",0,new Object()); //隨便一個對象就能夠，List 之類的

/**
     * 以Ajax方式輸出常規操做結果
     *
     * @param status
     *            返回狀態，200表示成功, 500表示錯誤
     * @param message
     *            操做結果描述
     * @param tag
     *            附加數據
     * @return
     */
    protected ActionResult ajaxResult(int status, final String message, Object tag) {
        JsonObject json = new JsonObject();
        json.addProperty("status", status);
        json.addProperty("message", message);

        String strJson = json.toString();

        if (tag != null) {
            StringBuffer sb = new StringBuffer();
            sb.append(strJson.substring(0, strJson.length() - 1));
            sb.append(",\"tag\":");
            sb.append(GsonUtils.toJsonWithGson(tag));
            sb.append("}");
            strJson = sb.toString();
        }

        return writeJson(strJson);
    }

/**
     * 向客戶端輸出文本信息
     *
     * @param message
     * @return
     */
    protected ActionResult write(final String message) {
        return new ActionResult() {
            @Override
            public void render(BeatContext arg0) throws Exception {
                beat.getResponse().setCharacterEncoding("UTF-8");
                beat.getResponse().setContentType("text/json;charset=UTF-8");
                PrintWriter out = beat.getResponse().getWriter();
                out.print(message);
                out.close();
            }

        };
    }

    /**
     * 向客戶端輸出文本信息
     *
     * @param message
     * @return
     */
    protected ActionResult writeText(final String message) {
        return new ActionResult() {
            @Override
            public void render(BeatContext arg0) throws Exception {
                beat.getResponse().setCharacterEncoding("UTF-8");
                beat.getResponse().setContentType("application/text");
                PrintWriter out = beat.getResponse().getWriter();
                out.print(message);
                out.close();
            }

        };
    }

GsonUtils.java

package com.xxx.xxx.common.util.gson;

import com.google.gson.*;

import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

public class GsonUtils {
    //private static Log logger = LogFactory.getLog(GsonUtils.class);
    public static String toJsonWithGson(Object obj) {
        Gson gson = createGson();   //new Gson();
        return gson.toJson(obj);
    }

    public static String toJsonWithGson(Object obj, Type type) {
        Gson gson = createGson();   //new Gson();
        return gson.toJson(obj, type);
    }

    @SuppressWarnings("unchecked")
    public static String toJsonWithGson(List list) {
        Gson gson = createGson();   //new Gson();
        return gson.toJson(list);
    }

    @SuppressWarnings("unchecked")
    public static String toJsonWithGson(List list, Type type) {
        Gson gson = createGson();   //new Gson();
        return gson.toJson(list, type);
    }

    public static String toJsonWithGsonBuilder(Object obj) {
        Gson gson = new GsonBuilder().setExclusionStrategies(new MyExclusionStrategy()).serializeNulls().create();
        return gson.toJson(obj);
    }

    public static String toJsonWithGsonBuilder(Object obj, Type type) {
        Gson gson = new GsonBuilder().setExclusionStrategies(new MyExclusionStrategy()).serializeNulls().create();
        return gson.toJson(obj, type);
    }

    @SuppressWarnings("unchecked")
    public static String toJsonWithGsonBuilder(List list) {
        Gson gson = new GsonBuilder().setExclusionStrategies(new MyExclusionStrategy()).serializeNulls().create();
        return gson.toJson(list);
    }

    @SuppressWarnings("unchecked")
    public static String toJsonWithGsonBuilder(List list, Type type) {
        Gson gson = new GsonBuilder().setExclusionStrategies(new MyExclusionStrategy()).serializeNulls().create();
        return gson.toJson(list, type);
    }

    public static <T> Object fromJson(String json, Class<T> clazz) {
        Object obj = null;
        try {
            Gson gson = new Gson();
            obj = gson.fromJson(json, clazz);
        } catch (Exception e) {
            //logger.error("fromJson方法轉換json串到實體類出錯", e);
        }
        return obj;
    }

    /**
     * 若是 Long 的數字超過15位，轉換爲String，在json中數字兩邊有引號
     * @return
     */
    private static Gson createGson(){
        GsonBuilder gsonBuilder = new GsonBuilder();
        LongSerializer serializer = new LongSerializer();
        gsonBuilder.registerTypeAdapter(Long.class, serializer);
        gsonBuilder.registerTypeAdapter(long.class, serializer);
        Gson gson = gsonBuilder.create();
        return gson;
    }

    public static void main(String... args) throws Exception{
//        long a = 12345678901234578L;
//
//        GsonBuilder builder = new GsonBuilder();
//        builder.registerTypeAdapter(Long.class, new LongSerializer());
//        Gson gson2 = builder.create();
//        System.out.println(gson2.toJson(a));
//
//        Gson gson = new GsonBuilder().setExclusionStrategies(new MyExclusionStrategy()).serializeNulls().create();
//        String str = gson.toJson(a);
//        System.out.println(str);

        TestVO vo = new TestVO();
        vo.setId(618708732263538688L);
        vo.setId2(918708732263538688L);
        System.out.println(toJsonWithGson(vo));

    }

    static class LongSerializer implements JsonSerializer<Long> {
        public JsonElement serialize(Long src, Type typeOfSrc, JsonSerializationContext context) {
            if(src!=null){
                String strSrc = src.toString();
                if(strSrc.length()>15){
                    return new JsonPrimitive(strSrc);
                }
            }
            return new JsonPrimitive(src);
        }
    }

    static class TestVO {
        public long getId() {
            return id;
        }

        public void setId(long id) {
            this.id = id;
        }

        private long id;

        public Long getId2() {
            return id2;
        }

        public void setId2(Long id2) {
            this.id2 = id2;
        }

        private Long id2;
    }
}

MyExclusionStrategy.java

package com.xxx.xxx.common.util.gson;

import com.google.gson.ExclusionStrategy;
import com.google.gson.FieldAttributes;

public class MyExclusionStrategy implements ExclusionStrategy {  
  
    private final Class<?> typeToSkip;  
      
    public MyExclusionStrategy(){  
        this.typeToSkip=null;  
    }  
      
    public MyExclusionStrategy(Class<?> typeToSkip) {  
        this.typeToSkip = typeToSkip;  
    }  
      
    public boolean shouldSkipClass(Class<?> clazz) {  
        return (clazz == typeToSkip);  
    }  
  
    public boolean shouldSkipField(FieldAttributes f) {  
        return f.getAnnotation(NotSerialize.class) != null;  
    }  
  
}

NotSerialize

package com.xxx.xxx.common.util.gson;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)  
@Target({ElementType.FIELD})  
public @interface NotSerialize {  
}