FastJson生成json时,显示Null属性

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FastJson生成json时，默认不会输出null字段。

移动端，有时候，需要后端提供完整的字段说明。

Map < String , Object > jsonMap = new HashMap< String , Object>();jsonMap.put("a",1);jsonMap.put("b","");jsonMap.put("c",null);jsonMap.put("d","wuzhuti.cn");String str = JSONObject.toJSONString(jsonMap);System.out.println(str);//输出结果:{"a":1,"b":"",d:"wuzhuti.cn"}

从输出结果可以看出，null对应的key已经被过滤掉；这明显不是我们想要的结果，这时我们就需要用到fastjson的SerializerFeature序列化属性

也就是这个方法：JSONObject.toJSONString(Object object, SerializerFeature... features)

Fastjson的SerializerFeature序列化属性

--来自oschina bfleeee博客

QuoteFieldNames———-输出key时是否使用双引号,默认为true
WriteMapNullValue——–是否输出值为null的字段,默认为false
WriteNullNumberAsZero—-数值字段如果为null,输出为0,而非null
WriteNullListAsEmpty—–List字段如果为null,输出为[],而非null
WriteNullStringAsEmpty—字符类型字段如果为null,输出为”“,而非null
WriteNullBooleanAsFalse–Boolean字段如果为null,输出为false,而非null

Map < String , Object > jsonMap = new HashMap< String , Object>();jsonMap.put("a",1);jsonMap.put("b","");jsonMap.put("c",null);jsonMap.put("d","wuzhuti.cn");String str = JSONObject.toJSONString(jsonMap,SerializerFeature.WriteMapNullValue);System.out.println(str);//输出结果:{"a":1,"b":"","c":null,"d":"wuzhuti.cn"}

Spring配置FastJson

<mvc:annotation-driven>
<mvc:message-converters>
<bean class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter">
<property name="supportedMediaTypes">
<list>
<value>application/json;charset=UTF-8</value>
</list>
</property>
<property name="features">
<list>
<value>DisableCircularReferenceDetect </value>
<value>WriteMapNullValue</value>
<value>WriteNullListAsEmpty</value>
<value>WriteNullStringAsEmpty</value>
<value>WriteNullNumberAsZero</value>
<value>WriteNullBooleanAsFalse</value>
</list>
</property>
</bean>
</mvc:message-converters>
</mvc:annotation-driven>

//模型

public class TopicVo implements Serializable {

private static final long serialVersionUID = 1L;

private Long id;

private String name;

private String nullName;
private Integer intName;
private Long longName;
private Double doubleName;
private Map mapName;
private List listName;
private Map mapNameWithValue = Maps.newHashMap();
private Map mapNameWithValue2 = Maps.newHashMap();
{
mapNameWithValue2.put("a", "a");
}
}

//json数据，空的转换成了null或者0或者空[]

{      "doubleName": 0,      "id": 17,      "intName": 0,      "listName": [],      "longName": 0,      "mapName": null,      "mapNameWithValue": {},      "mapNameWithValue2": {        "a": "a"      },      "name": "好像的",      "nullName": ""    }

完整的选项

package com.alibaba.fastjson.serializer;/** * @author wenshao[szujobs@hotmail.com] */public enum SerializerFeature {    QuoteFieldNames,    /**     *      */    UseSingleQuotes,    /**     *      */    WriteMapNullValue,    /**     * 用枚举toString()值输出     */    WriteEnumUsingToString,    /**     * 用枚举name()输出     */    WriteEnumUsingName,    /**     *      */    UseISO8601DateFormat,    /**     * @since 1.1     */    WriteNullListAsEmpty,    /**     * @since 1.1     */    WriteNullStringAsEmpty,    /**     * @since 1.1     */    WriteNullNumberAsZero,    /**     * @since 1.1     */    WriteNullBooleanAsFalse,    /**     * @since 1.1     */    SkipTransientField,    /**     * @since 1.1     */    SortField,    /**     * @since 1.1.1     */    @Deprecated    WriteTabAsSpecial,    /**     * @since 1.1.2     */    PrettyFormat,    /**     * @since 1.1.2     */    WriteClassName,    /**     * @since 1.1.6     */    DisableCircularReferenceDetect,    /**     * @since 1.1.9     */    WriteSlashAsSpecial,    /**     * @since 1.1.10     */    BrowserCompatible,    /**     * @since 1.1.14     */    WriteDateUseDateFormat,    /**     * @since 1.1.15     */    NotWriteRootClassName,    /**     * @since 1.1.19     */    DisableCheckSpecialChar,    /**     * @since 1.1.35     */    BeanToArray,    /**     * @since 1.1.37     */    WriteNonStringKeyAsString,        /**     * @since 1.1.42     */    NotWriteDefaultValue,        /**     * @since 1.2.6     */    BrowserSecure,        /**     * @since 1.2.7     */    IgnoreNonFieldGetter    ;

参考资料：https://wuzhuti.cn/2175.html

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