Jackson忽略ACCEPT_EMPTY_STRING_AS_NULL_OBJECT[重复]

Question

在Spring MVC中，我需要将空字符串(“”)视为null。这是因为我发现，当我编辑一个表单字段（带有Angular的ng-model)，该字段最初是未定义的，然后将其擦除为空白时，Angular将以空字符串的形式发送该bean属性。如果我不接触这样的null值，它将不会在JSON有效负载中发送，因此被视为null。

<bean id="jacksonMessageConverter" class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
    <constructor-arg>
        <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
            <property name="featuresToDisable">
                <array>
                    <util:constant static-field="com.fasterxml.jackson.databind.SerializationFeature.WRITE_DATES_AS_TIMESTAMPS" />
                </array>
            </property>
            <property name="featuresToEnable">
                <array>
                    <util:constant static-field="com.fasterxml.jackson.databind.SerializationFeature.INDENT_OUTPUT" />
                    <util:constant static-field="com.fasterxml.jackson.databind.SerializationFeature.WRITE_ENUMS_USING_TO_STRING" />
                    <util:constant static-field="com.fasterxml.jackson.databind.DeserializationFeature.READ_ENUMS_USING_TO_STRING" />
                    <util:constant static-field="com.fasterxml.jackson.databind.DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT" />
                </array>
            </property>
            <property name="serializationInclusion">
                <util:constant static-field="com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL" />
            </property>
        </bean>
    </constructor-arg>
    <property name="supportedMediaTypes">
        <array>
            <value>application/json</value>
        </array>
    </property>
</bean>

{
   "id":"ADMIN.NOTIFIER_SMTP",
   "host":"aa.bb.cc",
   "protocol":"POP",
   "securityProtocol":"PLAIN",
   "username":"", <----- shall be null on server, I don't care about client
   "passwordSet":false
}

Answer 1

您可能想编写一个CustomObjectMapper

<mvc:annotation-driven>
    <mvc:message-converters>
        <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
            <property name="objectMapper">
                <bean class="custom.CustomObjectMapper"/>
            </property>
        </bean>
    </mvc:message-converters>
</mvc:annotation-driven>

并在其中添加上面的反序列化器。