servlet服務器

在項目中的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">
<!--    配置全局參數 那個servlet對象均可以拿，這裏的是全局的參數-->

        <context-param>
            <param-name>gloableparam</param-name>
            <param-value>全局參數</param-value>
        </context-param>


<!--   告訴servlet這個名字     -->
        <servlet>
            <servlet-name>servelt</servlet-name>
            <servlet-class>com.hei.servelt</servlet-class>
        </servlet>
<!--        註冊servelt的映射，經過訪問url這個路徑，訪問這個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中的代碼：

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();
        // 獲取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")); // 根據值獲取單個value
        // 獲取web xml 下的全部init參數名
        Enumeration<String> names = config.getInitParameterNames();
        // 遍歷枚舉類型
        while (names.hasMoreElements()){
            // 獲取鍵
            String s = names.nextElement();
            System.out.println("配置文件的init參數的鍵： " + s);
            // 根據鍵獲取值
            String value = config.getInitParameter(s);
            System.out.println("配置文件的init參數的值： " + value);
        }
    }
    
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

獲取全局參數的方法

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


        // 指向同一個內存地址，能夠獲取全局配置地址。
        ServletContext s = getServletContext();
        String globa = s.getInitParameter("gloableparam");
        System.out.println("這個params爲：" + globa); //這個params爲：全局參數
    }

獲取tomcat的相對路徑

文件的下載：

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);
        //先把文件塞進去
        FileInputStream fileInputStream = new FileInputStream(realPath);

        // 構造輸出流對象
        ServletOutputStream outputStream = resp.getOutputStream();
        int len = 0;
        byte[] bytes = new byte[1024];
        while ((len=fileInputStream.read(bytes)) != -1){
            // 將塞進去的文件從新塞進去新的輸出流
            outputStream.write(bytes,0,len);
        }
        outputStream.close();
        fileInputStream.close();

    }
}