FastJson配置全局LocalDateTime序列化

最近工作中使用到了JDK1.8 time包，逐步取代以前的Date类，相比以前，time包的API的确好用多了，相关内容在网上有很多，就不累赘了。

但是有点蛋疼的地方在于LocalDateTime支持ISO8601标准，即[2018-10-10T05:51:31.924Z]。在MVC中，习惯性用[yyyy-MM-dd HH:mm:ss]。

好在Spring带有注解。如：

@DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss)
private LocalDateTime ldt;

​​@RequestParam(required = false) @DateTimeFormat(pattern = "yyyy-MM-dd") LocalDate date​​

​​
​​

参数在Param上，可以使用@DateTimeFormat在参数或者参数实体的属性上。对于参数在body上，则可以通过自定义拓展Formatter或者Converter<String, LocalDateTime>，网上也有很多，这里就提供一下代码

@Configuration
public class LocalDateTimeFormatConfig {

<span >@Bean</span>
<span >public</span> Formatter<span class="token generics function"><span ><</span>LocalDate<span >></span></span> <span >localDateFormatter</span><span >(</span><span >)</span> <span >{</span>
    <span >return</span> <span >new</span> <span >Formatter</span><span class="token generics function"><span ><</span>LocalDate<span >></span></span><span >(</span><span >)</span> <span >{</span>
        <span >@Override</span>
        <span >public</span> <span >@Nullable</span> String <span >print</span><span >(</span><span >@Nullable</span> LocalDate object<span >,</span> <span >@Nullable</span> Locale locale<span >)</span> <span >{</span>
            <span >if</span> <span >(</span>Objects<span >.</span><span >isNull</span><span >(</span>object<span >)</span><span >)</span><span >{</span>
                <span >return</span> null<span >;</span>
            <span >}</span>
            <span >return</span> object<span >.</span><span >format</span><span >(</span>DateTimeFormatter<span >.</span><span >ofPattern</span><span >(</span><span >"yyyy-MM-dd"</span><span >)</span><span >)</span><span >;</span>
        <span >}</span>

        <span >@Override</span>
        <span >public</span> <span >@Nullable</span> LocalDate <span >parse</span><span >(</span><span >@Nullable</span> String text<span >,</span> <span >@Nullable</span> Locale locale<span >)</span> <span >{</span>
            <span >if</span> <span >(</span><span >!</span>StringUtils<span >.</span><span >hasText</span><span >(</span>text<span >)</span><span >)</span> <span >{</span>
                <span >return</span> null<span >;</span>
            <span >}</span>
            <span >return</span> LocalDate<span >.</span><span >parse</span><span >(</span>text<span >,</span> DateTimeFormatter<span >.</span><span >ofPattern</span><span >(</span><span >"yyyy-MM-dd"</span><span >)</span><span >)</span><span >;</span>
        <span >}</span>
    <span >}</span><span >;</span>
<span >}</span>

<span >@Bean</span>
<span >public</span> Formatter<span class="token generics function"><span ><</span>LocalDateTime<span >></span></span> <span >localDateTimeFormatter</span><span >(</span><span >)</span> <span >{</span>
    <span >return</span> <span >new</span> <span >Formatter</span><span class="token generics function"><span ><</span>LocalDateTime<span >></span></span><span >(</span><span >)</span> <span >{</span>
        <span >@Override</span>
        <span >public</span> <span >@Nullable</span> String <span >print</span><span >(</span><span >@Nullable</span> LocalDateTime object<span >,</span> <span >@Nullable</span> Locale locale<span >)</span> <span >{</span>
            <span >if</span> <span >(</span>Objects<span >.</span><span >isNull</span><span >(</span>object<span >)</span><span >)</span><span >{</span>
                <span >return</span> null<span >;</span>
            <span >}</span>
            <span >return</span> object<span >.</span><span >format</span><span >(</span>DateTimeFormatter<span >.</span><span >ofPattern</span><span >(</span><span >"yyyy-MM-dd HH:mm:ss"</span><span >)</span><span >)</span><span >;</span>
        <span >}</span>

        <span >@Override</span>
        <span >public</span> <span >@Nullable</span> LocalDateTime <span >parse</span><span >(</span><span >@Nullable</span> String text<span >,</span> <span >@Nullable</span> Locale locale<span >)</span> <span >{</span>
            <span >if</span> <span >(</span><span >!</span>StringUtils<span >.</span><span >hasText</span><span >(</span>text<span >)</span><span >)</span> <span >{</span>
                <span >return</span> null<span >;</span>
            <span >}</span>
            <span >return</span> LocalDateTime<span >.</span><span >parse</span><span >(</span>text<span >,</span> DateTimeFormatter<span >.</span><span >ofPattern</span><span >(</span><span >"yyyy-MM-dd HH:mm:ss"</span><span >)</span><span >)</span><span >;</span>
        <span >}</span>
    <span >}</span><span >;</span>
<span >}</span>

<span >@Bean</span>
<span >public</span> Formatter<span class="token generics function"><span ><</span>LocalTime<span >></span></span> <span >localTimeFormatter</span><span >(</span><span >)</span> <span >{</span>
    <span >return</span> <span >new</span> <span >Formatter</span><span class="token generics function"><span ><</span>LocalTime<span >></span></span><span >(</span><span >)</span> <span >{</span>
        <span >@Override</span>
        <span >public</span> <span >@Nullable</span> String <span >print</span><span >(</span><span >@Nullable</span> LocalTime object<span >,</span> <span >@Nullable</span> Locale locale<span >)</span> <span >{</span>
            <span >if</span> <span >(</span>Objects<span >.</span><span >isNull</span><span >(</span>object<span >)</span><span >)</span><span >{</span>
                <span >return</span> null<span >;</span>
            <span >}</span>
            <span >return</span> object<span >.</span><span >format</span><span >(</span>DateTimeFormatter<span >.</span><span >ofPattern</span><span >(</span><span >"HH:mm:ss"</span><span >)</span><span >)</span><span >;</span>
        <span >}</span>

        <span >@Override</span>
        <span >public</span> <span >@Nullable</span> LocalTime <span >parse</span><span >(</span><span >@Nullable</span> String text<span >,</span> <span >@Nullable</span> Locale locale<span >)</span> <span >{</span>
            <span >if</span> <span >(</span><span >!</span>StringUtils<span >.</span><span >hasText</span><span >(</span>text<span >)</span><span >)</span> <span >{</span>
                <span >return</span> null<span >;</span>
            <span >}</span>
            <span >return</span> LocalTime<span >.</span><span >parse</span><span >(</span>text<span >,</span> DateTimeFormatter<span >.</span><span >ofPattern</span><span >(</span><span >"HH:mm:ss"</span><span >)</span><span >)</span><span >;</span>
        <span >}</span>
    <span >}</span><span >;</span>
<span >}</span>

​​
​​

​​}​​

​​
​​

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public class LocalDateTimeConvertConfig {

<span >private</span> String dateTimePattern <span >=</span> <span >"yyyy-MM-dd HH:mm:ss"</span><span >;</span>
<span >private</span> String datePattern <span >=</span> <span >"yyyy-MM-dd"</span><span >;</span>

<span >@Bean</span>
<span >public</span> Converter<span class="token generics function"><span ><</span>String<span >,</span> LocalDateTime<span >></span></span> <span >LocalDateTimeConvert</span><span >(</span><span >)</span> <span >{</span>
    <span >return</span> source <span >-</span><span >></span> <span >{</span>
        DateTimeFormatter df <span >=</span> DateTimeFormatter<span >.</span><span >ofPattern</span><span >(</span>dateTimePattern<span >)</span><span >;</span>
        LocalDateTime date <span >=</span> null<span >;</span>
        <span >try</span> <span >{</span>
            date <span >=</span> LocalDateTime<span >.</span><span >parse</span><span >(</span>source<span >,</span> df<span >)</span><span >;</span>
        <span >}</span> <span >catch</span> <span >(</span><span >Exception</span> e<span >)</span> <span >{</span>
            e<span >.</span><span >printStackTrace</span><span >(</span><span >)</span><span >;</span>
        <span >}</span>
        <span >return</span> date<span >;</span>
    <span >}</span><span >;</span>
<span >}</span>

<span >@Bean</span>
<span >public</span> Converter<span class="token generics function"><span ><</span>String<span >,</span> LocalDate<span >></span></span> <span >localDateConverter</span><span >(</span><span >)</span> <span >{</span>
    <span >return</span> source <span >-</span><span >></span> <span >{</span>
        DateTimeFormatter df <span >=</span> DateTimeFormatter<span >.</span><span >ofPattern</span><span >(</span>datePattern<span >)</span><span >;</span>
        LocalDate date <span >=</span> null<span >;</span>
        <span >try</span> <span >{</span>
            date <span >=</span> LocalDate<span >.</span><span >parse</span><span >(</span>source<span >,</span>df<span >)</span><span >;</span>
        <span >}</span><span >catch</span> <span >(</span><span >Exception</span> e<span >)</span><span >{</span>
            e<span >.</span><span >printStackTrace</span><span >(</span><span >)</span><span >;</span>
        <span >}</span>
        <span >return</span> date<span >;</span>
    <span >}</span><span >;</span>
<span >}</span>

<span >// 这里是使用JackSon全局序列化LocalDateTime,而我使用是FastJso,蛋疼</span>
<span >@Bean</span>
<span >public</span> LocalDateTimeSerializer <span >localDateTimeDeserializer</span><span >(</span><span >)</span> <span >{</span>
    <span >return</span> <span >new</span> <span >LocalDateTimeSerializer</span><span >(</span>DateTimeFormatter<span >.</span><span >ofPattern</span><span >(</span>dateTimePattern<span >)</span><span >)</span><span >;</span>
<span >}</span>

<span >@Bean</span>
<span >public</span> Jackson2ObjectMapperBuilderCustomizer <span >jackson2ObjectMapperBuilderCustomizer</span><span >(</span><span >)</span> <span >{</span>
    <span >return</span> builder <span >-</span><span >></span> builder<span >.</span><span >serializerByType</span><span >(</span>LocalDateTime<span >.</span><span >class</span><span >,</span> <span >localDateTimeDeserializer</span><span >(</span><span >)</span><span >)</span><span >;</span>
<span >}</span>

​​
​​

​​}​​

​​
​​

这里要说的问题就是现在工作项目中遇到的问题，使用的FastJson，而不是MVC默认的JackSon，在序列化LocalDateTime输出到前端时候，是[2018-10-10T05:51:31.924Z]，而想要输出的是yyyy-MM-dd HH:mm:ss格式，至此我们需要定制LocalDateTime类的序列化。我们一样可以使用注解解决，使用FastJson的@JSONField(format = “yyyy-MM-dd HH:mm:ss”)，在需要特殊序列化的成员属性上。

为了减少注解的使用，尝试是否可以让FastJson默认根据我们的规则去序列化LocalDateTime类。

首先祭出常规的FastJsonConfig：

  FastJsonConfig fastJsonConfig = new FastJsonConfig();
  fastJsonConfig.setSerializerFeatures(
  SerializerFeature.PrettyFormat,
  SerializerFeature.WriteMapNullValue,
  ...
  SerializerFeature.WriteNullStringAsEmpty);
fastJsonConfig.setCharset(Charset.forName("utf-8"));
...

使用ValueFilter：

ValueFilter valueFilter = (o, s, o1) -> {
    if (null == o1) {
        o1 = "";
    }
    if (o1 instanceof LocalDateTime){
        o1 = ((LocalDateTime) o1).format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
    }
    return o1;
};
fastJsonConfig.setSerializeFilters(valueFilter);
// 缺点，这是过滤级别的序列化，序列化的结果取决于o1的值，如将LocalDateTime类型的o1转换为String类型的o1，后续将不会调用LocalDateTime的序列化器，因为已经不是LocalDateTime类型了

指定fastJsonConfig的DateFormat：

fastJsonConfig.setDateFormat("yyyy-MM-dd HH:mm:ss");
...
// 缺点，指定后，将不会使用@JSONField注解上的format属性，包括并不限于Date类，LocalDateTime类，LocalDate类。（慎用）

自定义LocalDateTimeSerializer实现ObjectSerializer接口，重写write方法：

public class LocalDateTimeSerializer implements ObjectSerializer {

<span >public</span> <span >static</span> <span >final</span> LocalDateTimeSerializer instance <span >=</span> <span >new</span> <span >LocalDateTimeSerializer</span><span >(</span><span >)</span><span >;</span>
<span >private</span> <span >static</span> <span >final</span> String defaultPattern <span >=</span> <span >"yyyy-MM-dd HH:mm:ss"</span><span >;</span>

<span >public</span> <span >LocalDateTimeSerializer</span><span >(</span><span >)</span> <span >{</span>
<span >}</span>

<span >@Override</span>
<span >public</span> <span >void</span> <span >write</span><span >(</span>JSONSerializer serializer<span >,</span> Object object<span >,</span> Object fieldName<span >,</span> Type fieldType<span >,</span> <span >int</span> features<span >)</span> <span >throws</span> IOException <span >{</span>
    SerializeWriter out <span >=</span> serializer<span >.</span>out<span >;</span>
    <span >if</span> <span >(</span>object <span >==</span> null<span >)</span> <span >{</span>
        out<span >.</span><span >writeNull</span><span >(</span><span >)</span><span >;</span>
    <span >}</span> <span >else</span> <span >{</span>
        LocalDateTime result <span >=</span> <span >(</span>LocalDateTime<span >)</span> object<span >;</span>
        out<span >.</span><span >writeString</span><span >(</span>result<span >.</span><span >format</span><span >(</span>DateTimeFormatter<span >.</span><span >ofPattern</span><span >(</span>defaultPattern<span >)</span><span >)</span><span >)</span><span >;</span>
    <span >}</span>
<span >}</span>

​​
​​

​​}​​

​​
​​

​​SerializeConfig serializeConfig = SerializeConfig.globalInstance;​​​​serializeConfig.put(LocalDateTime.class, LocalDateTimeSerializer.instance);​ ​​​fastJsonConfig.setSerializeConfig(serializeConfig);​ ​

​​
​​

​​// 缺点，@JSONField注解一样会失效，仅限于LocalDateTime类​​​​...​​

​​
​​

如果使用的是JackSon，只需要在实例化LocalDateTimeSerializer的时候，指定一个DateTimeFormatter即可，方便很多，FastJson完败，有可能是我学艺不精，毕竟我是菜鸡。