required=false：@RequestParam defaultValue和required=false不影响

Question

我已经阅读了有关这个问题的每一个主题，并且我知道要使rest端点可用而不设置@RequestParam，需要在其中设置required=false。我还知道在版本4.1中仍然存在一个bug，并且这个参数不会影响控制器的行为，所以defaultValue参数应该完成这个工作。但这两种方法对我来说都不管用:我同时尝试了defaultValue和required，甚至尝试了它们的不同顺序--如果不将这些参数放在get地址中，我仍然可以得到Status 400 Bad Request。那么解决办法是什么呢？谢谢。我的代码如下：

public class Controller {
@ResponseBody
    @RequestMapping(value = "/api/", params = { "param"}, method = RequestMethod.GET, produces = { "application/json" })
    public Results show(HttpServletRequest request, HttpServletResponse response,
            @RequestParam(value = "param", defaultValue = "all", required=false)) {
        return null;
    }
}

Pom.xml的一部分：

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${org.springframework-version}</version>
            <exclusions>
                <!-- Exclude Commons Logging in favor of SLF4j -->
                <exclusion>
                    <groupId>commons-logging</groupId>
                    <artifactId>commons-logging</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>${org.springframework-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${org.springframework-version}</version>
            <scope>test</scope>
        </dependency>

和web.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    version="2.5">
    <context-param>
        <param-name>contextClass</param-name>
        <param-value>
        org.springframework.web.context.support.AnnotationConfigWebApplicationContext
    </param-value>
    </context-param>

    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>


    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>com.demshin.medpro.configuration.WebAppConfiguration</param-value>
    </context-param>

    <servlet>
        <servlet-name>springServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextClass</param-name>
            <param-value>org.springframework.web.context.support.AnnotationConfigWebApplicationContext</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>springServlet</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
</web-app>

和javaconfig：

@EnableWebMvc
@Configuration
@ComponentScan("com")
@Import(MySQLconfiguration.class)
public class WebAppConfiguration extends WebMvcConfigurerAdapter {

    @Bean
    public MappingJackson2HttpMessageConverter jacksonMessageConverter() {
        MappingJackson2HttpMessageConverter messageConverter = new MappingJackson2HttpMessageConverter();

        ObjectMapper mapper = new ObjectMapper();
        // Registering Hibernate4Module to support lazy objects
        mapper.registerModule(new Hibernate4Module());

        messageConverter.setObjectMapper(mapper);
        return messageConverter;

    }

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        // Here we add our custom-configured HttpMessageConverter
        converters.add(jacksonMessageConverter());
        super.configureMessageConverters(converters);
    }

    @Bean
    @Description("Thymeleaf template resolver serving HTML 5")
    public ServletContextTemplateResolver templateResolver() {
        ServletContextTemplateResolver templateResolver = new ServletContextTemplateResolver();
        templateResolver.setPrefix("/WEB-INF/html/");
        templateResolver.setSuffix(".html");
        templateResolver.setTemplateMode("HTML5");
        return templateResolver;
    }

    @Bean
    @Description("Thymeleaf template engine with Spring integration")
    public SpringTemplateEngine templateEngine() {
        SpringTemplateEngine templateEngine = new SpringTemplateEngine();
        templateEngine.setTemplateResolver(templateResolver());
        return templateEngine;
    }

    @Bean
    @Description("Thymeleaf view resolver")
    public ThymeleafViewResolver viewResolver() {
        ThymeleafViewResolver viewResolver = new ThymeleafViewResolver();
        viewResolver.setTemplateEngine(templateEngine());
        viewResolver.setContentType("text/html; charset=UTF-8");
        return viewResolver;
    }

    @Bean
    @Description("Spring message resolver")
    public ResourceBundleMessageSource messageSource() {
        ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
        messageSource.setBasename("/WEB-INF/i18n/messages");
        return messageSource;
    }

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/resources/**").addResourceLocations("/WEB-INF/resources/");
    }
}

Answer 1

问题是您已经在params = { "param"}级别中显式地指定了@RequestMapping，它将被继承到它的较低级别。这意味着这应该在请求中。

有问题的例子是：

    @ResponseBody
    @RequestMapping(value = "/api", params = { "param"},method = RequestMethod.GET, produces = { "application/json" })
    public String show(@RequestParam(value = "param", defaultValue = "all", required=false) String param, @RequestParam(value = "newparam", defaultValue = "all", required=false) String newparam) {
        return param+newparam;
    }

在这里，我将newparam声明为RequestParam，并给出请求为optional.So：

http://localhost:8080/api?param=test

会起作用的。但是，如果我们避免param请求，它将给出400，因为400已经在RequestMapping中声明了，所以它应该在请求中存在。需要在或@RequestParam中指定请求param。这意味着声明上述方法的正确方法是：

更正：

    @ResponseBody
    @RequestMapping(value = "/api", params = { "param"},method = RequestMethod.GET, produces = { "application/json" })
    public String show(String param, @RequestParam(value = "newparam", defaultValue = "all", required=false) String newparam) {
        return param+newparam;
    }

简单地说，解决问题的方法是从params = { "param"} @RequestMapping中删除。

所以我不认为这是春天的虫子