浅析Spring MVC:自定义配置

使用Spring Web MVC，开发者可以直接访问官方文档Spring Web MVC文档Version 5.2.1.RELEASE，本文及Spring MVC系列文章都参考于此文档及源码。

这一节主要为Spring MVC的配置，这也是我们最常用的。

1. 启用

可以使用@EnableWebMvc注解启用MVC配置

@Configuration
@EnableWebMvc
public class WebConfig {
}

可以使用<mvc:annotation-driven>xml配置启用MVC配置
```
<mvc:annotation-driven/>
```

2. Api

可以使用实现WebMvcConfigurer进行配置

@Configuration
@EnableWebMvc
public class WebConfig implements WebMvcConfigurer {

    // Implement configuration methods...
}

3. 类型

Spring MVC已经包含了数字转换@NumberFormat，时间转换@DateTimeFormat。我们可以自定义类型转换:

@Override
public void addFormatters(FormatterRegistry registry) {
    // ...
}

4. 校验

@Override
    public Validator getValidator() {
        // ...
    }

5. 拦截器

注册拦截器：

@Override
public void addInterceptors(InterceptorRegistry registry) {
    registry.addInterceptor(new LocaleChangeInterceptor());
    registry.addInterceptor(new ThemeChangeInterceptor()).addPathPatterns("/**").excludePathPatterns("/admin/**");
    registry.addInterceptor(new SecurityInterceptor()).addPathPatterns("/secure/*");
}

6. 内容

@Override
public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
    configurer.mediaType("json", MediaType.APPLICATION_JSON);
    configurer.mediaType("xml", MediaType.APPLICATION_XML);
}

7. 消息

可以重写configureMessageConverters()或extendMessageConverters()来自定义HttpMessageConverter实现数据转换

@Configuration
@EnableWebMvc
public class WebConfiguration implements WebMvcConfigurer {

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder()
                .indentOutput(true)
                .dateFormat(new SimpleDateFormat("yyyy-MM-dd"))
                .modulesToInstall(new ParameterNamesModule());
        converters.add(new MappingJackson2HttpMessageConverter(builder.build()));
        converters.add(new MappingJackson2XmlHttpMessageConverter(builder.createXmlMapper(true).build()));
    }
}

<mvc:annotation-driven>
    <mvc:message-converters>
        <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
            <property name="objectMapper" ref="objectMapper"/>
        </bean>
        <bean class="org.springframework.http.converter.xml.MappingJackson2XmlHttpMessageConverter">
            <property name="objectMapper" ref="xmlMapper"/>
        </bean>
    </mvc:message-converters>
</mvc:annotation-driven>

<bean id="objectMapper" class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean"
      p:indentOutput="true"
      p:simpleDateFormat="yyyy-MM-dd"
      p:modulesToInstall="com.fasterxml.jackson.module.paramnames.ParameterNamesModule"/>

<bean id="xmlMapper" parent="objectMapper" p:createXmlMapper="true"/>

8. 视图

@Override
public void addViewControllers(ViewControllerRegistry registry) {
    registry.addViewController("/").setViewName("home");
}

<mvc:view-controller path="/" view-name="home"/>

9. 解析器

@Override
public void addViewControllers(ViewControllerRegistry registry) {
    registry.addViewController("/").setViewName("home");
}

10. 静态文件

@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
    registry.addResourceHandler("/resources/**")
        .addResourceLocations("/public", "classpath:/static/")
        .setCachePeriod(31556926);
}

11. 默认Servlet

@Override
public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
    configurer.enable();
}

12. 路径匹配

@Override
public void configurePathMatch(PathMatchConfigurer configurer) {
    configurer
        .setUseSuffixPatternMatch(true)
        .setUseTrailingSlashMatch(false)
        .setUseRegisteredSuffixPatternMatch(true)
        .setPathMatcher(antPathMatcher())
        .setUrlPathHelper(urlPathHelper())
        .addPathPrefix("/api",
                HandlerTypePredicate.forAnnotation(RestController.class));
}

13. more

@EnableWebMvc为程序提供配置，检测委托WebMvcConfigurer实现自定义配置。
去除@EnableWebMvc,WebMvcConfigurer，继承扩展DelegatingWebMvcConfiguration可实现更多高级配置。

@Configuration
public class WebConfig extends DelegatingWebMvcConfiguration {

    // ...
}

xml:

@Component
public class MyPostProcessor implements BeanPostProcessor {

    public Object postProcessBeforeInitialization(Object bean, String name) throws BeansException {
        // ...
    }
}

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