Today, when writing code, some data was found to be scrambled during request fetching, as shown in the figure

Entity class A

public class BaseItems{

    private Integer id;
    //Other attributes omitted
    private Set<BasePolicy> policys;
}

Entity class B

public class BasePolicy implements java.io.Serializable {

    private Long id;
    private String grade;  //File level
    private String title;//Title
    private String fileno; //Symbol
    private String dispatchDep; //Dispatch unit
    //Other attributes omitted
}

The relationship of a b is one to many. When querying a data, the data of associated b will be queried together

Reason for the problem: there is a circular reference problem when serializing the list data json. In short, circular reference is caused by the mutual reference of multiple elements / attributes in the collection / object.

Solution: add the following code to the spring configuration file

<mvc:annotation-driven>
    <mvc:message-converters register-defaults="true">
        <bean class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter">
            <property name="supportedMediaTypes">
                <list>
                    <value>text/html;charset=UTF-8</value>
                    <value>application/json</value> 
                    <value>application/xml;charset=UTF-8</value>  
                </list>
            </property>
            <property name="features">
                <array>
                    <value>DisableCircularReferenceDetect</value>
                </array>
            </property> 
        </bean>
 </mvc:message-converters>
</mvc:annotation-driven>
<!-- Solution use fastJson Appear in $ref problem(Quote)  -->
<!-- jQuery This front-end technology cannot resolve the reference -->
<!-- Disable circular reference detection -->
<bean id="DisableCircularReferenceDetect"
    class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean">
    <property name="staticField"
        value="com.alibaba.fastjson.serializer.SerializerFeature.DisableCircularReferenceDetect">                           
    </property>
</bean>

The results are as follows: