如何使用 Spring Boot 注册 servlet？

这段代码不起作用

我有一个 web.xml 需要翻译成 spring boot

    <servlet>       
            <servlet-name>page-resolver</servlet-name>       
            <servlet-class>com.bk.ForwardServlet</servlet-class>         
            <init-param>
                <param-name>page</param-name>
                <param-value>/index.jsp</param-value>         
            </init-param>         
    </servlet>
    <servlet-mapping>                            
        <servlet-name>page-resolver</servlet-name>         
        <url-pattern>/index.html</url-pattern>
        <url-pattern>/login</url-pattern>
        <url-pattern>/qmgr/*</url-pattern>  
    </servlet-mapping>

和这个班级

@WebServlet
public class ForwardServlet extends HttpServlet {

private String page;

@Override
public void init(ServletConfig config) throws ServletException {
    super.init(config);
    page = config.getInitParameter("page");
}

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    req.getRequestDispatcher(page).forward(req, resp);
}
}

我编写了注册这个 bean 的代码，但它不起作用，我不明白为什么

@Configuration
public class ConfigureWeb implements ServletContextInitializer {

private void registerServlet(ServletContext servletContext) {
    ServletRegistrationBean serviceServlet =
            new ServletRegistrationBean(new ForwardServlet(), "/index.html","/login","/qmgr/*");

    serviceServlet.addUrlMappings("/index.jsp");
}

@Override
public void onStartup(ServletContext servletContext) throws ServletException {
    registerServlet(servletContext);
}
}

首先检查并验证所有资源是否保存在正确的目录中。对于 spring-boot，jsp 页面将保存在该目录中src->main->webapp->WEB-INF->view->*.jsp .

使用嵌入式 tomcat 时，您应该在 pom 中添加以下依赖项才能正确编译 jsp：

<!-- JSTL -->
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>jstl</artifactId>
</dependency>
<!-- To compile JSP files -->
<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-jasper</artifactId>
    <scope>provided</scope>
</dependency>

现在我们需要告诉 spring jsp 文件所在的位置，我们可以有两种方法：

在 application.properties 中添加条目

spring.mvc.view.prefix=/WEB-INF/view/
spring.mvc.view.suffix=.jsp

在这里我们可以指定 jsp 文件所在的文件夹，并定义视图。 或者

配置InternalResourceViewResolver以提供JSP页面

@Configuration
@EnableWebMvc
@ComponentScan
public class MvcConfiguration extends WebMvcConfigurerAdapter
{
    @Override
    public void configureViewResolvers(ViewResolverRegistry registry) {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("/WEB-INF/view/");
        resolver.setSuffix(".jsp");
        resolver.setViewClass(JstlView.class);
        registry.viewResolver(resolver);
    }
}

Now for 注册 servlets :

ServletRegistrationBean用于注册 ServletServlet 3.0 +容器。我们需要创建一个 beanServletRegistrationBean在我们的 JavaConfig.查找 ServletRegistrationBean 的一些用于配置 Servlet 的方法。设置Servlet（）：设置要注册的 servlet。addUrlMappings():添加 Servlet 的 URL 映射。设置启动时加载：设置启动时加载 Servlet 的优先级。

假设我们有两个 ServletHelloCountryServlet and HelloStateServlet然后我们将使用 ServletRegistrationBean 在 Spring Boot 中注册它们，如下所示：

@Configuration
public class WebConfig {
   @Bean    
   public ServletRegistrationBean<HttpServlet> countryServlet() {
       ServletRegistrationBean<HttpServlet> servRegBean = new ServletRegistrationBean<>();
       servRegBean.setServlet(new HelloCountryServlet());
       servRegBean.addUrlMappings("/country/*");
       servRegBean.setLoadOnStartup(1);
       return servRegBean;
   }
   @Bean    
   public ServletRegistrationBean<HttpServlet> stateServlet() {
       ServletRegistrationBean<HttpServlet> servRegBean = new ServletRegistrationBean<>();
       servRegBean.setServlet(new HelloStateServlet());
       servRegBean.addUrlMappings("/state/*");
       servRegBean.setLoadOnStartup(1);
       return servRegBean;
   }   
}  

我们为每个 Servlet 创建一个Servlet注册Bean豆。 Servlet 类将如下所示：

public class HelloCountryServlet extends HttpServlet   {
    private static final long serialVersionUID = 1L;
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException{
        doGet(request,response);
    }
        public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
            response.setContentType("text/html");
            PrintWriter out = response.getWriter();
        out.println("<h3>Hello India!</h3>");   
    }
}

这是一种方法。

另一种方法在 spring-boot 中注册 servlet 是使用注释：@ServletComponentScan and @WebServlet. @ServletComponentScan在Spring Boot中将扫描带有注释的Servlet@WebServlet, 过滤器注释为@WebFilter和听众注释@WebListener注释@ServletComponentScan用于类级别的JavaConfig。 @ServletComponentScan 扫描 Servlet、过滤器和监听器仅使用嵌入式 Web 服务器。找到带有 @WebServlet 注释的 Servlet。

所以越早HelloCountryServletservlet 可以提供为：

@WebServlet(urlPatterns = "/country/*", loadOnStartup = 1)
public class HelloCountryServlet extends HttpServlet   {
    private static final long serialVersionUID = 1L;
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException{
         doGet(request,response);
    }
        public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
             response.setContentType("text/html");
             PrintWriter out = response.getWriter();
         out.println("<h3>Hello India!</h3>");  
    }
}

并提供 ServletComponentScan 注释，例如：

@ServletComponentScan
@SpringBootApplication
public class SpringBootAppStarter {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootAppStarter.class, args);
    }
}