CODEWITHSUNDEEP
spring-boot
zhuguowei
zhuguowei

Reputation: 8477

Spring boot how to custom HttpMessageConverter

Back-end, Spring boot project(v1.3.0.RELEASE), supply Rest JSON Api to fron-end, just now encountered an error:

Infinite recursion (StackOverflowError)

I decide to change to a custom FastJsonHttpMessageConverter, and code is below

@Bean
public HttpMessageConverter httpMessageConverter() {
    FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();

    return fastJsonHttpMessageConverter;
}

but it does not work, in real it uses a default HttpMessageConverter. Although does not have above error, the output is not as I expected. e.g.

suppliers: [
    {
        $ref: "$.value"
    }
]

Now change above code 

@Bean
public HttpMessageConverter mappingJackson2HttpMessageConverter() {
    FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();
    return fastJsonHttpMessageConverter;
}

This time it works, I want to know why the method name have to be mappingJackson2HttpMessageConverter? If use another method name how to configure it?

Upvotes: 2

Views: 24681

Answers (2)

zhuguowei
zhuguowei

Reputation: 8477

After seeing this offical document, I know how to customize converters.

@Bean
public HttpMessageConverters customConverters() {
    HttpMessageConverter<?> additional = new FastJsonHttpMessageConverter();
    return new HttpMessageConverters(additional);
}

A Revise to my main post, actually below code does not work.

@Bean
public HttpMessageConverter mappingJackson2HttpMessageConverter() {
    FastJsonHttpMessageConverter fastJsonHttpMessageConverter = new FastJsonHttpMessageConverter();
    return fastJsonHttpMessageConverter;
}

Spring boot never enter this method if you set breakpoint inside it.

And below code also works.

@SpringBootApplication
public class FooApplication extends WebMvcConfigurerAdapter {


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

  @Override
  public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    super.configureMessageConverters(converters);
    converters.add(new FastJsonHttpMessageConverter());
  }

}

Upvotes: 6

Assen Kolov
Assen Kolov

Reputation: 4393

Spring boot says (https://docs.spring.io/spring-boot/docs/current/reference/html/howto-spring-mvc.html#howto-customize-the-responsebody-rendering):

If a bean you add is of a type that would have been included by default anyway (like MappingJackson2HttpMessageConverter for JSON conversions) then it will replace the default value.

The bean you are adding is not of the same type, so the above does not happen. Your converter goes somewhere in the list of converters (probably the end), and the first suitable converter (the old one) does the job.

Beans produced by the Java configuration have the name of the method, so when you create a second bean named mappingJackson2HttpMessageConverter, it overrides the one created by spring boot's JacksonHttpMessageConvertersConfiguration and takes it place.

Instead of adding a converter bean, you might prefer to override the whole list of converters:

As in normal MVC usage, any WebMvcConfigurerAdapter beans that you provide can also contribute converters by overriding the configureMessageConverters method,

Upvotes: 4

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