JAVA-EE解析ServletConfig接口的作用和方法------计算机网络经典

古城微笑少年丶 2024-03-02 09:39 96阅读 0赞

> transient表示游离的意思,不可被序列化的
> 加一个序列号可以在类名相同的情况下实现区分
> 一个Servlet对象对应一个ServletConfig对象
> 一百个Servlet对象就有一百个ServletConfig对象
> ServletConfig对象是谁创建的,在什么时候创建的
> Tomcat服务器(web容器)创建了ServletConfig对象
> 通过反射机制创建了Servlet对象,再通过init就传值到了Servlet内,并完成了赋值
> 这个ServletConfig是Servlet的配置信息对象
> web.xml里面我们注册的servlet配置信息就会被包装成一个ServletConfig对象
> 将<servlet>标签内的信息包装到ServletConfig对象中
> 
> transient表示游离的意思,不可被序列化的 
> 加一个序列号可以在类名相同的情况下实现区分 
> 一个Servlet对象对应一个ServletConfig对象 
> 一百个Servlet对象就有一百个ServletConfig对象 
> ServletConfig对象是谁创建的,在什么时候创建的 
> Tomcat服务器(web容器)创建了ServletConfig对象 
> 通过反射机制创建了Servlet对象,再通过init就传值到了Servlet内,并完成了赋值 
> 这个ServletConfig是Servlet的配置信息对象 
> web.xml里面我们注册的servlet配置信息就会被包装成一个ServletConfig对象 
> 将<servlet>标签内的信息包装到ServletConfig对象中

> <?xml version="1.0" encoding="UTF-8"?>
> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
> xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
> version="4.0">
> <servlet>
> <servlet-name>studentServlet</servlet-name>
> <servlet-class>com.bjpowernode.javaweb.servlet.StudentServlet</servlet-class>
> </servlet>
> <servlet-mapping>
> <servlet-name>studentServlet</servlet-name>
> <url-pattern>/student</url-pattern>
> </servlet-mapping>
> <servlet>
> <servlet-name>LoginServlet</servlet-name>
> <servlet-class>com.bjpowernode.javaweb.servlet.LoginServlet</servlet-class>
> </servlet>
> <servlet-mapping>
> <servlet-name>LoginServlet</servlet-name>
> <url-pattern>/LoginServlet</url-pattern>
> </servlet-mapping>
> <servlet>
> <servlet-name>VipServlet</servlet-name>
> <servlet-class>com.bjpowernode.javaweb.servlet.VipServlet</servlet-class>
> </servlet>
> <servlet-mapping>
> <servlet-name>VipServlet</servlet-name>
> <url-pattern>/VipServlet</url-pattern>
> </servlet-mapping>
> <servlet>
> <servlet-name>UserServlet</servlet-name>
> <servlet-class>com.bjpowernode.javaweb.servlet.UserServlet</servlet-class>
> </servlet>
> <servlet-mapping>
> <servlet-name>UserServlet</servlet-name>
> <url-pattern>/UserServlet</url-pattern>
> </servlet-mapping>
> <servlet>
> <servlet-name>ConfigServletTest</servlet-name>
> <servlet-class>com.bjpowernode.javaweb.servlet0.ConfigServletTest</servlet-class>
> 
> 
> <init-param>
> <param-name>driver</param-name>
> <param-value>com.mysql.jdbc.Driver</param-value>
> </init-param>
> <init-param>
> <param-name>url</param-name>
> <param-value>jdbc:mysql://localhost:13306/powernode</param-value>
> </init-param>
> <init-param>
> <param-name>user</param-name>
> <param-value>root</param-value>
> </init-param>
> <init-param>
> <param-name>password</param-name>
> <param-value>abc123</param-value>
> </init-param>
> </servlet>
> <servlet-mapping>
> <servlet-name>ConfigServletTest</servlet-name>
> <url-pattern>/ConfigServletTest</url-pattern>
> </servlet-mapping>
> <servlet>
> <servlet-name>ConfigServletTest1</servlet-name>
> <servlet-class>com.bjpowernode.javaweb.servlet0.ConfigServletTest1</servlet-class>
> 
> <init-param>
> <param-name>driver</param-name>
> <param-value>com.mysql.jdbc.Driver</param-value>
> </init-param>
> <init-param>
> <param-name>url</param-name>
> <param-value>jdbc:mysql://localhost:13306/powernode</param-value>
> </init-param>
> <init-param>
> <param-name>user</param-name>
> <param-value>root</param-value>
> </init-param>
> <init-param>
> <param-name>password</param-name>
> <param-value>abc123</param-value>
> </init-param>
> </servlet>
> <servlet-mapping>
> <servlet-name>ConfigServletTest1</servlet-name>
> <url-pattern>/ConfigServletTest1</url-pattern>
> </servlet-mapping>
> </web-app>
> 
> <?xml version="1.0" encoding="UTF-8"?>
> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
> xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
> version="4.0">
> <servlet>
> <servlet-name>studentServlet</servlet-name>
> <servlet-class>com.bjpowernode.javaweb.servlet.StudentServlet</servlet-class>
> </servlet>
> <servlet-mapping>
> <servlet-name>studentServlet</servlet-name>
> <url-pattern>/student</url-pattern>
> </servlet-mapping>
> <servlet>
> <servlet-name>LoginServlet</servlet-name>
> <servlet-class>com.bjpowernode.javaweb.servlet.LoginServlet</servlet-class>
> </servlet>
> <servlet-mapping>
> <servlet-name>LoginServlet</servlet-name>
> <url-pattern>/LoginServlet</url-pattern>
> </servlet-mapping>
> <servlet>
> <servlet-name>VipServlet</servlet-name>
> <servlet-class>com.bjpowernode.javaweb.servlet.VipServlet</servlet-class>
> </servlet>
> <servlet-mapping>
> <servlet-name>VipServlet</servlet-name>
> <url-pattern>/VipServlet</url-pattern>
> </servlet-mapping>
> <servlet>
> <servlet-name>UserServlet</servlet-name>
> <servlet-class>com.bjpowernode.javaweb.servlet.UserServlet</servlet-class>
> </servlet>
> <servlet-mapping>
> <servlet-name>UserServlet</servlet-name>
> <url-pattern>/UserServlet</url-pattern>
> </servlet-mapping>
> <servlet>
> <servlet-name>ConfigServletTest</servlet-name>
> <servlet-class>com.bjpowernode.javaweb.servlet0.ConfigServletTest</servlet-class>
> 
> 
> <init-param>
> <param-name>driver</param-name>
> <param-value>com.mysql.jdbc.Driver</param-value>
> </init-param>
> <init-param>
> <param-name>url</param-name>
> <param-value>jdbc:mysql://localhost:13306/powernode</param-value>
> </init-param>
> <init-param>
> <param-name>user</param-name>
> <param-value>root</param-value>
> </init-param>
> <init-param>
> <param-name>password</param-name>
> <param-value>abc123</param-value>
> </init-param>
> </servlet>
> <servlet-mapping>
> <servlet-name>ConfigServletTest</servlet-name>
> <url-pattern>/ConfigServletTest</url-pattern>
> </servlet-mapping>
> <servlet>
> <servlet-name>ConfigServletTest1</servlet-name>
> <servlet-class>com.bjpowernode.javaweb.servlet0.ConfigServletTest1</servlet-class>
> 
> <init-param>
> <param-name>driver</param-name>
> <param-value>com.mysql.jdbc.Driver</param-value>
> </init-param>
> <init-param>
> <param-name>url</param-name>
> <param-value>jdbc:mysql://localhost:13306/powernode</param-value>
> </init-param>
> <init-param>
> <param-name>user</param-name>
> <param-value>root</param-value>
> </init-param>
> <init-param>
> <param-name>password</param-name>
> <param-value>abc123</param-value>
> </init-param>
> </servlet>
> <servlet-mapping>
> <servlet-name>ConfigServletTest1</servlet-name>
> <url-pattern>/ConfigServletTest1</url-pattern>
> </servlet-mapping>
> </web-app>

> package com.bjpowernode.javaweb.servlet0;
> 
> import jakarta.servlet.*;
> 
> import java.io.IOException;
> import java.io.PrintWriter;
> import java.util.Enumeration;
> 
> public class ConfigServletTest extends GenericServlet
> {
> @Override
> public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
> servletResponse.setContentType("text/html;charset=UTF-8");
> PrintWriter writer = servletResponse.getWriter();
> //ServletConfig是什么?
> //是Servlet规范中的一员
> //获取ServletConfig对象
> ServletConfig servletConfig = this.getServletConfig();
> writer.println("该对象是" + servletConfig);
> //换成jetty之类的web容器,包名和类名不一样了,但是还是实现了一样的方法
> writer.println(" ");
> writer.println(servletConfig.getServletName());
> writer.println(" ");
> writer.println(servletConfig.getServletContext());
> writer.println(" ");
> //<init-param>这个配置信息会被包装进ServletConfig内部
> //我们可以通过ServletConfig获取到这个初始化参数信息
> Enumeration<String> initParameterNames = servletConfig.getInitParameterNames();
> //是否有更多元素
> while (initParameterNames.hasMoreElements())
> {
> String name = initParameterNames.nextElement();
> String initParameter = servletConfig.getInitParameter(name);
> writer.println(name + ":" + initParameter);
> writer.println(" ");
> }
> }
> }
> 
> package com.bjpowernode.javaweb.servlet0;
> 
> import jakarta.servlet.*;
> 
> import java.io.IOException;
> import java.io.PrintWriter;
> import java.util.Enumeration;
> 
> public class ConfigServletTest extends GenericServlet
> {
> @Override
> public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
> servletResponse.setContentType("text/html;charset=UTF-8");
> PrintWriter writer = servletResponse.getWriter();
> //ServletConfig是什么?
> //是Servlet规范中的一员
> //获取ServletConfig对象
> ServletConfig servletConfig = this.getServletConfig();
> writer.println("该对象是" + servletConfig);
> //换成jetty之类的web容器,包名和类名不一样了,但是还是实现了一样的方法
> writer.println(" ");
> writer.println(servletConfig.getServletName());
> writer.println(" ");
> writer.println(servletConfig.getServletContext());
> writer.println(" ");
> //<init-param>这个配置信息会被包装进ServletConfig内部
> //我们可以通过ServletConfig获取到这个初始化参数信息
> Enumeration<String> initParameterNames = servletConfig.getInitParameterNames();
> //是否有更多元素
> while (initParameterNames.hasMoreElements())
> {
> String name = initParameterNames.nextElement();
> String initParameter = servletConfig.getInitParameter(name);
> writer.println(name + ":" + initParameter);
> writer.println(" ");
> }
> }
> }