How to autowire default XmlMapper in Spring Boot application

Question

I'm having some issues autowiring the default Jackson XmlMapper in one of my Spring Boot projects. I've created a simple example project that illustrates this.

What I'm doing here is roughly based on this:

http://docs.spring.io/spring-boot/docs/1.2.2.RELEASE/reference/htmlsingle/#howto-write-an-xml-rest-service

http://docs.spring.io/spring-boot/docs/1.2.2.RELEASE/reference/htmlsingle/#howto-customize-the-jackson-objectmapper

From pom.xml

<!-- ... -->

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.2.2.RELEASE</version>
</parent>

<!-- ... -->

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.dataformat</groupId>
        <artifactId>jackson-dataformat-xml</artifactId>
    </dependency>
</dependencies>

<!-- ... -->

The main class:

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

The Demo POJO, not specifying @XmlRootElement, so it won't use JAXB:

@JsonInclude(Include.NON_NULL)
public class Demo {
    private String stringProperty;
    private int intProperty;
    public String getStringProperty() {
        return stringProperty;
    }
    public void setStringProperty(String stringProperty) {
        this.stringProperty = stringProperty;
    }
    public int getIntProperty() {
        return intProperty;
    }
    public void setIntProperty(int intProperty) {
        this.intProperty = intProperty;
    }
}

The Demo Controller:

@RestController
public class DemoController {
    @Autowired 
    private ObjectMapper objectMapper;
    // @Autowired 
    // private XmlMapper xmlMapper;

    @RequestMapping(value = "/demo", method = RequestMethod.GET)
    public Demo getDemo() {
        Demo demo = new Demo();
        demo.setStringProperty("Hello world!");
        demo.setIntProperty(42);
        return demo;
    }
}

Everything works fine the way it is, depending on Accept headers, either JSON or XML will be returned.

I can easily autowire the default ObjectMapper configured by Spring Boot. So far so good.

If I comment in the autowiring of the XmlMapper I get:

Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.fasterxml.jackson.dataformat.xml.XmlMapper] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1301)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1047)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:942)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:533)
... 18 more

Any idea why this is? I would have assumed it to work the same way as the ObjectMapper. Just to clarify, I don't want to customise the mappers, I simply want a reference to the default ones created by Spring Boot.

Answer 1

Based on the answer by @Andy Wilkinson I did some more digging and found a way to get at what I wanted. Spring Boot does not expose the XmlMapper as a Bean but it does expose the message converter it is used in, which is MappingJackson2XmlHttpMessageConverter. So I could auto-wire that bean and get the ObjectMapper (which is now an XmlMapper) from it.

The Demo Controller from my question now looks like this:

    @RestController
    public class DemoController {
        @Autowired 
        private ObjectMapper objectMapper;
        @Autowired
        private MappingJackson2XmlHttpMessageConverter xmlConverter;

        @RequestMapping(value = "/demo", method = RequestMethod.GET)
        public Demo getDemo() {
            Demo demo = new Demo();
            demo.setStringProperty("Hello world!");
            demo.setIntProperty(42);
            ObjectMapper xmlMapper = xmlConverter.getObjectMapper();
            return demo;
        }
    }