整合web层技术

导入 servlet 依赖

Servlet-Specification Jar，Servlet 规范包，经过版本升级命名有变化：

• 3.1 之前的 Servlet API 叫 servlet-api
• 3.1 之后的 Servlet API 叫 javax.servlet-api ```xml javax.servlet servlet-api 2.5 provided

javax.servlet javax.servlet-api 4.0.1 provided

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### 整合Servlet
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#### 通过注解扫描完成Servlet组件的注册：@WebServlet
1、创建Servlet：
```java
@WebServlet(name = "FirstServlet",urlPatterns = "/first")
public class DemoServlet01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("第一个Servlet启动");
        resp.getWriter().print("Hello");
    }
}

2、修改启动类：

@SpringBootApplication
@ServletComponentScan // 在Spring Boot启动时会扫描@WebServlet注解，并将该类实例化
public class DemoForSpringBootBasicApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoForSpringBootBasicApplication.class, args);
    }
}

通过方法完成Servlet组件的注册

1、创建 Servlet

public class DemoServlet02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("第二个Servlet启动");
        resp.getWriter().print("Hello ，I am second");
    }
}

2、创建Servlet配置类

@Configuration
public class ServletConfig {
    @Bean
    public ServletRegistrationBean getServletRegistrationBean() {
        return new ServletRegistrationBean(new DemoServlet02(), "/second");
    }
}

整合filter

通过注解扫描完成Filter组件的注册：@WebFilter

1、创建Filter：

@WebFilter(filterName = "first",urlPatterns = {"/first"})
public class DemoFilter01 implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("First Filter初始化");
    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("进入First Filter");
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println("离开First Filter");
    }
    @Override
    public void destroy() {
        System.out.println("First Filter结束");
    }
}

2、修改启动类：

@SpringBootApplication
@ServletComponentScan // 在Spring Boot启动时会扫描@WebFilter注解，并将该类实例化
public class DemoForSpringBootBasicApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoForSpringBootBasicApplication.class, args);
    }
}

通过方法完成Filter组件的注册

1、创建Filter

@WebFilter(filterName = "second",urlPatterns = {"/second"})
public class DemoFilter02 implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("Second Filter初始化");
    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("进入Second Filter");
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println("离开Second Filter");
    }
    @Override
    public void destroy() {
        System.out.println("Second Filter结束");
    }
}
public class DemoServlet02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("第二个Servlet启动");
        resp.getWriter().print("Hello ，I am second");
    }
}

2、创建Filter配置类

@Configuration
public class FilterConfig {
    @Bean
    public FilterRegistrationBean getFilterRegistrationBean(){
        FilterRegistrationBean bean = new FilterRegistrationBean(new DemoFilter02());
//        bean.addUrlPatterns(new String[]{"/second","*.action"});
        bean.addUrlPatterns("/second");
        return bean;
    }
}

整合listener

通过注解扫描完成Listener组件注册

1、创建Listener：

@WebListener
public class DemoListener01 implements ServletContextListener {
    @Override
    public void contextDestroyed(ServletContextEvent sce) {
    }
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.out.println("Servlet Context初始化！");
    }
}

2、修改配置类

@SpringBootApplication
@ServletComponentScan // 在Spring Boot启动时会扫描@WebListener注解，并将该类实例化
public class DemoForSpringBootBasicApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoForSpringBootBasicApplication.class, args);
    }
}

通过方法完成Listener组件注册

1、编写Listener：

public class DemoListener02 implements ServletContextListener {
    @Override
    public void contextDestroyed(ServletContextEvent sce) {
    }
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.out.println("Servlet Context初始化！");
    }
}

2、配置Listener启动类

@Configuration
public class ListenerConfig {
    @Bean
    public ServletListenerRegistrationBean getListener(){
        return new ServletListenerRegistrationBean(new DemoListener02());
    }
}