增加配置:

package com.wm.auth.config;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.CorsRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

import java.text.SimpleDateFormat;
import java.util.Iterator;
import java.util.List;

/***
 * @ClassName: WebAppConfigurer
 * @Description: 跨域本地測試, 線上使用nginx處理
 * @Author: wm_yu
 * @Create_time: 15:01 2020-3-13
 */
@Configuration
public class WebAppConfigurer implements WebMvcConfigurer {

    /**
     * 跨域處理
     * @param registry
     */
    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")
                .allowedOrigins("*")
                //.allowedOrigins("http://192.168.89.89")
                //rest集中請求方式
                .allowedMethods("GET", "POST","DELETE")
                .allowCredentials(false).maxAge(36000);
    }

     @Override
     public void addResourceHandlers(ResourceHandlerRegistry registry) {
                 registry.addResourceHandler("swagger-ui.html")
                         .addResourceLocations("classpath:/META-INF/resources/");

                 registry.addResourceHandler("/webjars/**")
                         .addResourceLocations("classpath:/META-INF/resources/webjars/");
             }


    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        Iterator<HttpMessageConverter<?>> iterator = converters.iterator();
        while(iterator.hasNext()){
            HttpMessageConverter<?> converter = iterator.next();
            if(converter instanceof MappingJackson2HttpMessageConverter){
                iterator.remove();
            }
        }
        MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
        mapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY);
        mapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));

        // 將long類型的數據轉爲String類型
        SimpleModule simpleModule = new SimpleModule();
        simpleModule.addSerializer(Long.class, ToStringSerializer.instance);
        simpleModule.addSerializer(Long.TYPE, ToStringSerializer.instance);
        simpleModule.addSerializer(long.class, ToStringSerializer.instance);
        mapper.registerModule(simpleModule);

        converter.setObjectMapper(mapper);

        converters.add(converter);
    }



}

效果:

{
  "code": 200,
  "msg": "操作成功",
  "data": [
    {
      "id": "4",
      "parentId": "-1",
      "sort": 0,
      "type": "md-home",
      "createDate": "2020-03-17 11:49:28",
      "modifyDate": "2020-03-17 11:49:28",
      "delFlag": 0,
      "text": "系統管理",
      "children": [
        {
          "id": "5",
          "name": "menu",
          "parentId": "4",
          "sort": 1,
          "type": "md-home",
          "createDate": "2020-03-17 14:02:20",
          "modifyDate": "2020-03-17 14:02:20",
          "delFlag": 0,
          "text": "菜單管理"
        },
        {
          "id": "1240211721989435393",
          "name": "roleAdmin",
          "parentId": "4",
          "sort": 2,
          "type": "md-home",
          "createDate": "2020-03-18 17:41:31",
          "modifyDate": "2020-03-18 17:41:31",
          "delFlag": 0,
          "text": "角色管理"
        }
      ]
    },
    {
      "id": "3",
      "name": "home",
      "parentId": "-1",
      "sort": 1,
      "type": "md-home",
      "createDate": "2020-03-17 11:34:07",
      "modifyDate": "2020-03-17 11:34:07",
      "delFlag": 0,
      "text": "主頁q"
    },
    {
      "id": "1",
      "parentId": "-1",
      "sort": 2,
      "type": "md-home",
      "createDate": "2020-03-17 11:19:35",
      "modifyDate": "2020-03-17 11:19:35",
      "delFlag": 0,
      "text": "二級菜單啊",
      "children": [
        {
          "id": "2",
          "name": "t1",
          "parentId": "1",
          "sort": 1,
          "type": "md-home",
          "createDate": "2020-03-17 11:20:06",
          "modifyDate": "2020-03-17 11:20:06",
          "delFlag": 0,
          "text": "表格"
        }
      ]
    }
  ]
}

可以看到完全去除了,null值/空值的屬性

下面是轉載的部分

首先在網絡上查看資料,開始配置時,老是不生效,最後看到這位大佬的文章:

記一次踩坑:springboot2.0.2配置fastjson不生效

最近在嘗試搭建springboot+dubbo+shiro基於註解的一個項目,突發奇想想把消息轉換器從jackson換成fastjson,於是就開始了折騰之路.

輕車熟路的去自定了一個SpringMvcConfigure去繼承WebMvcConfigurerAdapter,然後就發現這個WebMvcConfigurerAdapter竟然過時了?what?點進去看源碼:

/**
 * An implementation of {@link WebMvcConfigurer} with empty methods allowing
 * subclasses to override only the methods they're interested in.
 *
 * @author Rossen Stoyanchev
 * @since 3.1
 * @deprecated as of 5.0 {@link WebMvcConfigurer} has default methods (made
 * possible by a Java 8 baseline) and can be implemented directly without the
 * need for this adapter
 */
@Deprecated
public abstract class WebMvcConfigurerAdapter implements WebMvcConfigurer {}

可以看到從spring5.0開始就被@Deprecated,原來是java8中支持接口中有默認方法,所以我們現在可以直接實現WebMvcConfigurer,然後選擇性的去重寫某個方法,而不用實現它的所有方法.

於是就實現了WebMvcConfigurer:

@Configuration
public class SpringMvcConfigure implements WebMvcConfigurer {

    /**
     * 配置消息轉換器
     * @param converters
     */
    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();
        //自定義配置...
        FastJsonConfig config = new FastJsonConfig();
        config.setSerializerFeatures(SerializerFeature.QuoteFieldNames,
                SerializerFeature.WriteEnumUsingToString,
                /*SerializerFeature.WriteMapNullValue,*/
                SerializerFeature.WriteDateUseDateFormat,
                SerializerFeature.DisableCircularReferenceDetect);
        fastJsonHttpMessageConverter.setFastJsonConfig(config);
        converters.add(fastJsonHttpMessageConverter);
    }

}

本以爲這樣子配置就可以完事兒,但是詭異的事情發生了,我明明註釋了SerializerFeature.WriteMapNullValue,可是返回的json中仍然有爲null的字段,然後我就去com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter中的write和writeInternal打了斷點,再次執行,竟然什麼都沒有發生,根本沒有走這兩個方法,於是在自定義的SpringMvcConfigure中configureMessageConverters方法內打了斷點,想看看這個方法參數converters裏邊到底有什麼:

看到這裏就想到,肯定是我自己添加的fastjson在後邊,所以沒有生效,所以就加了以下代碼:

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    converters = converters.stream()
                .filter((converter)-> !(converter instanceof MappingJackson2HttpMessageConverter))
                .collect(Collectors.toList());
    FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();
    //自定義配置...
    FastJsonConfig config = new FastJsonConfig();
    config.setSerializerFeatures(SerializerFeature.QuoteFieldNames,
            SerializerFeature.WriteEnumUsingToString,
            /*SerializerFeature.WriteMapNullValue,*/
            SerializerFeature.WriteDateUseDateFormat,
            SerializerFeature.DisableCircularReferenceDetect);
    fastJsonHttpMessageConverter.setFastJsonConfig(config);
    converters.add(fastJsonHttpMessageConverter);
}

竟然還沒有生效,後來開始追蹤,開始方法是從org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport類中的一個bean配置:

@Bean
public RequestMappingHandlerAdapter requestMappingHandlerAdapter() {
    RequestMappingHandlerAdapter adapter = createRequestMappingHandlerAdapter();
    adapter.setContentNegotiationManager(mvcContentNegotiationManager());
    //就是從這裏開始設置converters的,然後從這裏一路追蹤下去.
    adapter.setMessageConverters(getMessageConverters());
    adapter.setWebBindingInitializer(getConfigurableWebBindingInitializer());
    adapter.setCustomArgumentResolvers(getArgumentResolvers());
    adapter.setCustomReturnValueHandlers(getReturnValueHandlers());

    if (jackson2Present) {
        adapter.setRequestBodyAdvice(Collections.singletonList(new JsonViewRequestBodyAdvice()));
        adapter.setResponseBodyAdvice(Collections.singletonList(new JsonViewResponseBodyAdvice()));
    }

    AsyncSupportConfigurer configurer = new AsyncSupportConfigurer();
    configureAsyncSupport(configurer);
    if (configurer.getTaskExecutor() != null) {
        adapter.setTaskExecutor(configurer.getTaskExecutor());
    }
    if (configurer.getTimeout() != null) {
        adapter.setAsyncRequestTimeout(configurer.getTimeout());
    }
    adapter.setCallableInterceptors(configurer.getCallableInterceptors());
    adapter.setDeferredResultInterceptors(configurer.getDeferredResultInterceptors());

    return adapter;
}

getMessageConverters()方法:

protected final List<HttpMessageConverter<?>> getMessageConverters() {
    if (this.messageConverters == null) {
        this.messageConverters = new ArrayList<>();
        configureMessageConverters(this.messageConverters);//進入這一步
        if (this.messageConverters.isEmpty()) {
            addDefaultHttpMessageConverters(this.messageConverters);
        }
        extendMessageConverters(this.messageConverters);
    }
    return this.messageConverters;
}

org.springframework.web.servlet.config.annotation.DelegatingWebMvcConfiguration:

@Override
protected void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    this.configurers.configureMessageConverters(converters);
}
@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    for (WebMvcConfigurer delegate : this.delegates) {
        delegate.configureMessageConverters(converters);
    }
}

this.delegates包含了springboot的一個默認配置類類:org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration裏邊有一個參數

private final HttpMessageConverters messageConverters;

for循環裏的delegate.configureMessageConverters(converters)調用了WebMvcAutoConfiguration中的configureMessageConverters方法:

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    converters.addAll(this.messageConverters.getConverters());
}

執行完這個後,就給converters中添加了10個轉換器了,就是上圖中的10個.
this.delegates中還有一個就是我們自定義的那個,執行完後,在我們自定義的那個SpringMvcConfigure發現我添加的fastjson添加進去了,但是org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport.getMessageConverters(),發現converters並沒有發現我們添加進去的FastJsonHttpMessageConverter,這時突然又想起來:java8的stream api每次都是生成一個新的對象,所以導致converters已經不是傳遞過來的那個converters的引用了(這裏也證明了java是值傳遞,不是引用傳遞).

於是再次改變那個lambda表達式爲普通的增強for循環:

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    /*converters = converters.stream().
            filter((converter)-> !(converter instanceof MappingJackson2HttpMessageConverter))
            .collect(Collectors.toList());*/
    for (HttpMessageConverter<?> converter : converters) {
        if (converter instanceof MappingJackson2HttpMessageConverter){
            converters.remove(converter);
        }
    }
    FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();
    //自定義配置...
    FastJsonConfig config = new FastJsonConfig();
    config.setSerializerFeatures(SerializerFeature.QuoteFieldNames,
            SerializerFeature.WriteEnumUsingToString,
            /*SerializerFeature.WriteMapNullValue,*/
            SerializerFeature.WriteDateUseDateFormat,
            SerializerFeature.DisableCircularReferenceDetect);
    fastJsonHttpMessageConverter.setFastJsonConfig(config);
    converters.add(fastJsonHttpMessageConverter);
}

再次運行,wtf?報錯了:ConcurrentModificationException,原來使用for循環遍歷過程中不能進行remove操作,於是換成Iterator:

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    /*converters = converters.stream()
            .filter((converter)-> !(converter instanceof MappingJackson2HttpMessageConverter))
            .collect(Collectors.toList());
    for (HttpMessageConverter<?> converter : converters) {
        if (converter instanceof MappingJackson2HttpMessageConverter){
            converters.remove(converter);
        }
    }*/
    Iterator<HttpMessageConverter<?>> iterator = converters.iterator();
    while(iterator.hasNext()){
        HttpMessageConverter<?> converter = iterator.next();
        if(converter instanceof MappingJackson2HttpMessageConverter){
            iterator.remove();
        }
    }
    FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();
    //自定義配置...
    FastJsonConfig config = new FastJsonConfig();
    config.setSerializerFeatures(SerializerFeature.QuoteFieldNames,
            SerializerFeature.WriteEnumUsingToString,
            /*SerializerFeature.WriteMapNullValue,*/
            SerializerFeature.WriteDateUseDateFormat,
            SerializerFeature.DisableCircularReferenceDetect);
    fastJsonHttpMessageConverter.setFastJsonConfig(config);
    converters.add(fastJsonHttpMessageConverter);
}

再次運行,我去,終於解決了,先是刪除MappingJackson2HttpMessageConverter,然後添加FastJsonHttpMessageConverter,但是不是到爲什麼進過一系列操作後,MappingJackson2HttpMessageConverter還是添加進去了,但是由於FastJsonHttpMessageConverter在MappingJackson2HttpMessageConverter之前添加,所以對結果不影響.至此,解決了這個問題.

總結

最重要的還是解決了springboot2.0.2配置fastjson不生效的問題
更加明白stream api返回的都是全新的對象
更理解java是值傳遞而不是引用傳遞
瞭解到想要在迭代過程中對集合進行操作要用Iterator,而不是直接簡單的for循環或者增強for循環

如有不正確的地方還請指出,謝謝.

轉載: spring boot定義返回json過濾null值/空值不序列化不生效

記一次踩坑:springboot2.0.2配置fastjson不生效

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