Spring MVC Jackson序列化引发NullPointer异常

Question

Note : I tried almost all the solution available, but still not able to get it working.

I am using Spring 4 in my application. I have added jackson libs in my pom as below :

<dependency>
                <groupId>com.fasterxml.jackson.core</groupId>
                <artifactId>jackson-core</artifactId>
                <version>2.2.1</version>
            </dependency>
            <dependency>
                <groupId>com.fasterxml.jackson.core</groupId>
                <artifactId>jackson-databind</artifactId>
                <version>2.2.1</version>
            </dependency>
            <dependency>
                <groupId>com.fasterxml.jackson.core</groupId>
                <artifactId>jackson-annotations</artifactId>
                <version>2.2.1</version>
            </dependency>
            <dependency>
                <groupId>org.codehaus.jackson</groupId>
                <artifactId>jackson-core-asl</artifactId>
                <version>1.9.9</version>
            </dependency>
            <dependency>
                <groupId>org.codehaus.jackson</groupId>
                <artifactId>jackson-mapper-asl</artifactId>
                <version>1.9.9</version>
            </dependency>

spring-config.xml looks like this(only part of it) :

<mvc:annotation-driven/>
    <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
        <property name="order" value="1"/>
        <property name="messageConverters">
            <list>
                <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                    <property name="supportedMediaTypes" value="application/json"/>
                </bean>
                <bean class="org.springframework.http.converter.StringHttpMessageConverter">
                    <property name="supportedMediaTypes" value="text/plain;charset=UTF-8"/>
                </bean>
            </list>
        </property>
    </bean>

Entity (Omitted the getters and setters)

@Entity(name="Employee")
public class Employee {

private String name;
private List<Address> addressList;

}
}

I am using @ResponseBody in my rest controller. I am creating an employee with only the name (no address provided). After the creation, I am trying to return the same object back to the UI. But in this case, the address list will be NULL. I am getting NullPointer Exception due to this.

I have tried annotating the address field with @JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL) and @JsonInclude(JsonInclude.Include.NON_NULL) . But in both of these cases also, I am getting the same exception.

I tried different ways. If I create a custom converter and use it in the controller, it works fine. But I do not want to write that code in all the controller methods.

Any solution ?

Answer 1

Finally, I decided to go with instantiating the the collection with ArrayList in the entities and it is working fine now. None of the other ways worked.