首先，解决两个小问题
1.输入中文乱码问题
一个小Demo即可解决：
package demo;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class DemoServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//设置response查询的码表
//response.setCharacterEncoding("UTF-8");
//通过一个头 Content-Type 告知客户端使用何种码表
//response.setHeader("Content-Type", "text/html;charset=UTF-8");
//以上两行可以简写成这样，Tomcat自动设置编码
response.setContentType("text/html;charset=UTF-8");
PrintWriter writer = response.getWriter();
//writer.write("hello response!!!");写英文不需要考虑编码问题
writer.write("你好");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
2.怎么在客户端页面看到图片
用到字节流，示例如下：
package demo;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ByteServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 使用response获得字节输出流
ServletOutputStream out = response.getOutputStream();
// 获得服务器上的图片
String realPath = this.getServletContext().getRealPath("a.jpg");
InputStream in = new FileInputStream(realPath);
// 字节数组提高效率
int len = 0;
byte[] buffer = new byte[1024];
while ((len = in.read(buffer)) > 0) {
out.write(buffer, 0, len);
}
in.close();
out.close();
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
接下来是文件下载案例：
WebContent目录下创建download文件夹，放入各种文件，以供下载
这里有两种方式下载：
1.<a>标签直接指向服务器资源，浏览器显示能解析的，解析不了的提供下载
这种方式只需要html代码即可（新建download.html）
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>使用a标签指向服务器上的资源</h1>
<a href="/WEB4/download/a.flv">a.flv</a>
<br />
<a href="/WEB4/download/a.jpg">a.jpg</a>
<br />
<a href="/WEB4/download/a.flv">a.mp3</a>
<br />
<a href="/WEB4/download/a.mp4">a.mp4</a>
<br />
<a href="/WEB4/download/a.txt">a.txt</a>
<br />
<a href="/WEB4/download/a.zip">a.zip</a>
<br />
<h1>使用服务器端编码的方式实现文件下载</h1>
<a href="/WEB4/downloadServlet?filename=a.flv">a.flv</a>
<br />
<a href="/WEB4/downloadServlet?filename=a.jpg">a.jpg</a>
<br />
<a href="/WEB4/downloadServlet?filename=a.mp3">a.mp3</a>
<br />
<a href="/WEB4/downloadServlet?filename=a.mp4">a.mp4</a>
<br />
<a href="/WEB4/downloadServlet?filename=a.txt">a.txt</a>
<br />
<a href="/WEB4/downloadServlet?filename=a.zip">a.zip</a>
<br />
</body>
</html>
2.使用服务器端编码的方式实现文件下载
package demo;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class DownloadServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 获得要下载文件名称
String filename = request.getParameter("filename");
// 下载的文件类型（MIME类型）
response.setContentType(this.getServletContext().getMimeType(filename));
// 告诉客户端该文件不是直接解析 而是以附件形式打开(下载)
response.setHeader("Content-Disposition", "attachment;filename=" + filename);
// 获取文件的绝对路径
String path = this.getServletContext().getRealPath("download/" + filename);
// 获得该文件输入流
InputStream in = new FileInputStream(path);
// 通过response获得输出流
ServletOutputStream out = response.getOutputStream();
// 文件拷贝
int len = 0;
byte[] buffer = new byte[1024];
while ((len = in.read(buffer)) > 0) {
out.write(buffer, 0, len);
}
in.close();
out.close();
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
原文地址：https://www.cnblogs.com/xuyiqing/p/8408718.html
时间： 2024-08-26 21:39:59