SpringMVC built by IDEA: No converter found for return value of type

Question

I use IDEA to build a simple RESTful server based on SpringMVC. But @RestController and @ResponseBody can't convert POJO to JSON by jackson JSON.

In dispatcher-servlet.xml :

<mvc:annotation-driven/>

In pom.xml :

    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-annotations</artifactId>
        <version>2.9.5</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>2.9.5</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.9.5</version>
    </dependency>

My controller:

@RestController
@RequestMapping("/test")
public class TestController {

    @GetMapping("/one")
    public One getOne() {
        return new One(1);
    }
}

My POJO:

public class One {
    public One(int number) {
        this.number = number;
    }

    public int getNumber() {
        return number;
    }

    public void setNumber(int number) {
        this.number = number;
    }

    private int number;

}

But I still get the No converter found for return value of type error. I don't know why. Have I met some config or something else?

Answer 1

Try putting this in your dispatcher-servlet.xml:

<mvc:annotation-driven>
     <mvc:message-converters>
            <bean class="org.springframework.http.converter.StringHttpMessageConverter"/>
            <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"/>
   </mvc:message-converters>
</mvc:annotation-driven>

Answer 2

You need to specify produces/consumes to define which type of data type you want, for example:

@RestController
@RequestMapping("/test", produces = {MediaType.APPLICATION_JSON_VALUE})
public class TestController {

    @GetMapping("/one")
    public One getOne() {
        return new One(1);
    }
}