尝试进行返回值处理

epmet-commons/epmet-commons-tools/src/main/java/com/epmet/commons/tools/security/config/WebMvcConfig.java

@@ -1,8 +1,8 @@
 /**
  * Copyright (c) 2018 人人开源 All rights reserved.
- *
+ * <p>
  * https://www.renren.io
- *
+ * <p>
  * 版权所有，侵权必究！
  */
 
@@ -11,10 +11,14 @@ package com.epmet.commons.tools.security.config;
 import com.epmet.commons.tools.security.resolver.LoginUserHandlerMethodArgumentResolver;
 import com.epmet.commons.tools.security.resolver.UserDetailHandlerMethodArgumentResolver;
 import com.epmet.commons.tools.utils.DateUtils;
+import com.fasterxml.jackson.core.JsonGenerator;
 import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.JsonSerializer;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializerProvider;
 import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
+import org.apache.commons.lang3.StringUtils;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -27,9 +31,10 @@ import org.springframework.http.converter.support.AllEncompassingFormHttpMessage
 import org.springframework.web.method.support.HandlerMethodArgumentResolver;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 
+import java.io.IOException;
+import java.lang.reflect.Field;
 import java.text.SimpleDateFormat;
-import java.util.List;
-import java.util.TimeZone;
+import java.util.*;
 
 /**
  * MVC配置
@@ -43,6 +48,7 @@ public class WebMvcConfig implements WebMvcConfigurer {
     private UserDetailHandlerMethodArgumentResolver userDetailHandlerMethodArgumentResolver;
     @Autowired
     private LoginUserHandlerMethodArgumentResolver loginUserHandlerMethodArgumentResolver;
+
     @Override
     public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
         argumentResolvers.add(loginUserHandlerMethodArgumentResolver);
@@ -75,6 +81,41 @@ public class WebMvcConfig implements WebMvcConfigurer {
         simpleModule.addSerializer(Long.TYPE, ToStringSerializer.instance);
         mapper.registerModule(simpleModule);
 
+        mapper.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>() {
+            @Override
+            public void serialize(Object value, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
+
+                String fieldName = jsonGenerator.getOutputContext().getCurrentName();
+                Field field = null;
+                try {
+                    //反射获取字段类型
+                    field = jsonGenerator.getCurrentValue().getClass().getDeclaredField(fieldName);
+                } catch (NoSuchFieldException e) {
+                    e.printStackTrace();
+                }
+
+                if (null != field) {
+                    if (Objects.equals(field.getType(), String.class)) {
+                        // 字符串型空值""
+                        jsonGenerator.writeString(StringUtils.EMPTY);
+                        return;
+                    } else if (Objects.equals(field.getType(), List.class)) {
+                        // 列表型空值返回[]
+                        jsonGenerator.writeStartArray();
+                        jsonGenerator.writeEndArray();
+                        return;
+                    } else if (Objects.equals(field.getType(), Map.class)) {
+                        // map型空值返回{}
+                        jsonGenerator.writeStartObject();
+                        jsonGenerator.writeEndObject();
+                        return;
+                    }
+                }
+
+                // 默认返回""
+                jsonGenerator.writeString(StringUtils.EMPTY);
+            }
+        });
         converter.setObjectMapper(mapper);
         return converter;
     }