java - Jackson如何自动获取模块bean？

Question

我正在上以下课

@SpringBootApplication
public class TestApplication {

    public static void main(final String[] args) {

        SpringApplication.run(TestApplication.class, args);
    }

    @Bean
    public Module jdk8Module() {
        return new Jdk8Module();
    }

    @Bean
    public Module guavaModule() {
        return new GuavaModule();
    }
} 

这里这两个bean自动注册到jackson ObjectMapper中。它是如何自动注册这个模块的？

Answer 1

这是由 Spring Boot JacksonAutoConfiguration 完成的类。

正如 javadoc 所说:

Auto configuration for Jackson. The following auto-configuration will get applied:

• an ObjectMapper in case none is already configured.
• a Jackson2ObjectMapperBuilder in case none is already configured.
• auto-registration for all Module beans with all ObjectMapper beans (including the defaulted ones).