以编程方式映射servlet，而不是使用web.xml或注释 [英] Map servlet programmatically instead of using web.xml or annotations

问题描述

如何在没有web.xml或注释的情况下以编程方式实现此映射?任务是不使用诸如spring之类的框架.

How can I implement this mapping programmatically without web.xml or annotations? The mission is not to use any framework like spring or something else.

<servlet>
    <servlet-name>hello</servlet-name>
    <servlet-class>test.HelloServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello</url-pattern>
</servlet-mapping>

推荐答案

从Servlet 3.0开始，您可以使用

Since Servlet 3.0 you can use ServletContext#addServlet() for this.

servletContext.addServlet("hello", test.HelloServlet.class);

根据您所开发的内容，有两个可以在其中运行此代码的钩子.

Depending on what you're developing, there are two hooks where you can run this code.

1. 如果要开发可公共重用的模块化Web片段JAR文件(例如JSF和Spring MVC等现有框架)，请使用

2. 或者，如果您将其用作WAR应用程序的内部集成部分，请使用

3. Or, if you're using it as an internally integrated part of your WAR application, then use a ServletContextListener.

   @WebListener
   public class YourFrameworkInitializer implements ServletContextListener {
   
       @Override
       public void contextInitialized(ServletContextEvent event) {
           event.getServletContext().addServlet("hello", test.HelloServlet.class);
       }
   
       // ...
   }
   

您只需确保您的web.xml与Servlet 3.0或更高版本兼容(因此与Servlet 2.5或更低版本兼容)，否则Servlet容器将以符合声明版本的后备方式运行，并且您将丢失所有Servlet 3.0功能.

You only need to make sure that your web.xml is compatible with Servlet 3.0 or newer (and thus not Servlet 2.5 or older), otherwise the servletcontainer will run in fallback modus complying the declared version and you will lose all Servlet 3.0 features.

<?xml version="1.0" encoding="UTF-8"?>
<web-app 
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0"
>
    <!-- Config here -->
</web-app>

另请参见:

• ServletContainerInitializer与ServletContextListener
• 带有Tomcat 7的@WebServlet注释
• 设计模式"基于Web的应用程序
• 将共享代码和web.xml从WAR项目拆分为通用JAR项目

See also:

• ServletContainerInitializer vs ServletContextListener
• @WebServlet annotation with Tomcat 7
• Design Patterns web based applications
• Splitting up shared code and web.xml from WAR project to common JAR project

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