在浏览器上实现下载文件(利用ServletContext的方法实现的功能)_接口请求contextdownload

案例：获取当前工程的资源

得到web目录下的某个图片资源在浏览器上显示出来

方法

案例：读取Web目录下的资源文件

步骤

1. 得到上下文对象
2. 通过上下文对象的方法读取web/WEB-INF/图片文件，转成一个输入流
3. 得到响应的字节输出流response.getOutputStream()
4. 将输入流中数据复制到输出流中
5. 关闭流

执行效果

代码

package com.itheima.servlet;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

@WebServlet(name = "Demo2Servlet", urlPatterns = "/demo2")
public class Demo2Servlet extends HttpServlet {
   
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
        //1. 得到上下文对象
        ServletContext application = getServletContext();
        //2. 通过上下文对象的方法读取web/WEB-INF/图片文件，转成一个输入流
        InputStream in = application.getResourceAsStream("/WEB-INF/cart504.jpg");
        //3. 得到响应的字节输出流response.getOutputStream()
        OutputStream out = response.getOutputStream();
        //4. 将输入流中数据复制到输出流中
        int len = 0;
        byte[] buf = new byte[1024];
        while((len=in.read(buf))!=-1) {
   
            out.write(buf,0,len);
        }
        //5. 关闭流
        in.close();
        out.close();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
        this.doPost(request, response);
    }
}
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改进代码

package com.itheima.servlet;

import org.apache.commons.io.IOUtils;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

@WebServlet(name = "Demo2Servlet", urlPatterns = "/demo2")
public class Demo2Servlet extends HttpServlet {
   
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
        //1. 得到上下文对象
        ServletContext application = getServletContext();
        //2. 通过上下文对象的方法读取web/WEB-INF/图片文件，转成一个输入流
        InputStream in = application.getResourceAsStream(</
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