SpringMVC返回json将null转为空字符串-马育民老师

# 说明

需要 jackson jar包或依赖

# java代码

```
package com.im.json;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;

import java.io.IOException;

public class JsonObjectMapper extends ObjectMapper {

private static final long serialVersionUID = 1L;

public JsonObjectMapper() {
        super();
        // 空值处理为空串
        this.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>() {
            @Override
            public void serialize(Object value, JsonGenerator jg, SerializerProvider sp) throws IOException, JsonProcessingException {
                jg.writeString("");
            }
        });
    }
}

```

# spring-web

增加下面内容：
```
	<mvc:annotation-driven>
		<mvc:message-converters>
			<bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
				<property name="objectMapper">
					<bean class="com.im.json.JsonObjectMapper"></bean>
				</property>
			</bean>
		</mvc:message-converters>
	</mvc:annotation-driven>
```

原文出处：http://malaoshi.top/show_1IX21MS8yEsA.html