servlet服务器

在项目中的web.xml配置servlet

<?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">
<!--    配置全局参数 那个servlet对象都可以拿，这里的是全局的参数-->

        <context-param>
            <param-name>gloableparam</param-name>
            <param-value>全局参数</param-value>
        </context-param>


<!--   告诉servlet这个名字     -->
        <servlet>
            <servlet-name>servelt</servlet-name>
            <servlet-class>com.hei.servelt</servlet-class>
        </servlet>
<!--        注册servelt的映射，通过访问url这个路径，访问这个servletd的名字 -->
        <servlet-mapping>
            <servlet-name>servelt</servlet-name>
            <url-pattern>/a</url-pattern>
        </servlet-mapping>

        <servlet>
            <servlet-name>Servlet03</servlet-name>
            <servlet-class>com.hei.Servlet03</servlet-class>
        </servlet>

        <servlet-mapping>
            <servlet-name>Servlet03</servlet-name>
            <url-pattern>/b</url-pattern>
        </servlet-mapping>

        <servlet>
            <servlet-name>ServletConfig</servlet-name>
            <servlet-class>com.hei.ServletConfigDemo</servlet-class>

            <init-param>
                <param-name>name</param-name>
                <param-value>beijing</param-value>
            </init-param>
            <init-param>
                <param-name>age</param-name>
                <param-value>18</param-value>
            </init-param>
            <init-param>
                <param-name>sex</param-name>
                <param-value>man</param-value>
            </init-param>
        </servlet>

        <servlet-mapping>  // 映射的路由
            <servlet-name>ServletConfig</servlet-name>
            <url-pattern>/ServletConfig</url-pattern>
        </servlet-mapping>


</web-app>

java中的代码：

package com.hei;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.ClientInfoStatus;
import java.util.Enumeration;

public class ServletConfigDemo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(req, resp);
        // 生成config方法
        ServletConfig config = getServletConfig();
        // 获取web xml下的config配置名字
        System.out.println("config的名字：" + config.getServletName()); //config的名字：ServletConfig

        System.out.println("------------------------------------");
        System.out.println(config.getInitParameter("name")); // 根据值获取单个value
        // 获取web xml 下的所有init参数名
        Enumeration<String> names = config.getInitParameterNames();
        // 遍历枚举类型
        while (names.hasMoreElements()){
            // 获取键
            String s = names.nextElement();
            System.out.println("配置文件的init参数的键： " + s);
            // 根据键获取值
            String value = config.getInitParameter(s);
            System.out.println("配置文件的init参数的值： " + value);
        }
    }
    
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

获取全局参数的方法

response.getWriter().append("Served at: ").append(request.getContextPath());


        // 指向同一个内存地址，可以获取全局配置地址。
        ServletContext s = getServletContext();
        String globa = s.getInitParameter("gloableparam");
        System.out.println("这个params为：" + globa); //这个params为：全局参数
    }

获取tomcat的相对路径

文件的下载：

public class DownLoad extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String filename = req.getParameter("filename");
        String realPath = getServletContext().getRealPath("down/" + filename);
        //先把文件塞进去
        FileInputStream fileInputStream = new FileInputStream(realPath);

        // 构造输出流对象
        ServletOutputStream outputStream = resp.getOutputStream();
        int len = 0;
        byte[] bytes = new byte[1024];
        while ((len=fileInputStream.read(bytes)) != -1){
            // 将塞进去的文件重新塞进去新的输出流
            outputStream.write(bytes,0,len);
        }
        outputStream.close();
        fileInputStream.close();

    }
}