response-设置响应体-getWriter
- （1）设置响应体的方法
- 1)getWriter()方法：字符流
只能向浏览器响应文本内容: 字符串，标签
为什么会产生中文乱码？Tomcat IOS 8859-1 - 2)getOutputStream()方法：字节流
可以向浏览器响应任何类型的数据: 图片，视频，音频
用于开发下载功能
src\com\wzx\pack04_body\Demo04Servlet.java
@WebServlet("/body")
public class Demo04Servlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1:字符流
response.setHeader("Content-Type","text/html;charset=utf-8");
response.getWriter().write("<font color='red'>中国</font>");
}
}
response-设置响应体-getOutputstream
（1）字节输出流
a：如果向页面输出字符串，不需要解决乱码
b: 向页面输出字符串时，使用write
src\com\wzx\pack04_body\Demo05Servlet.java
写字符串一般使用字符流，但是必须要处理编码。而使用字节流能搞定字符串？能~且不需要处理编码，但是字节流真正的作用是写文件数据
@WebServlet("/body2")
public class Demo05Servlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取字节输出流
ServletOutputStream outputStream = response.getOutputStream();
//写数据到浏览器
byte[] bytes = "中国".getBytes();
outputStream.write(bytes);
//关闭
outputStream.close();
}
}
response-设置响应体-图片的复制
test\java\com\wzx\service\TestFileService.java
public class TestFileService {
@Test//1:导入junit
public void test01() throws IOException {
//文件复制
String file1 = "a.jpg";
String file2 = "b.jpg";
InputStream inputStream =TestFileService.class.getClassLoader().getResourceAsStream("a.jpg");
File file = new File(file2);
file.createNewFile();
OutputStream outputStream = new FileOutputStream("b.jpg");
//1：创建文件业务类
FileService fileService = new FileService();
//2:调用业务方法copy
fileService.copy(inputStream,outputStream);
//3：关闭流
inputStream.close();
outputStream.close();
}
}
src\com\wzx\service\FileService.java
//文件业务类
public class FileService {
//复制文件
public void copy(InputStream inputStream, OutputStream outputStream) throws IOException {
//边读边写
//1:字节数组 缓冲区
byte[] buffer=new byte[1024];
int len = 0;
//2:边读边写
while ((len=inputStream.read(buffer))!=-1){
outputStream.write(buffer,0,len);
}
}
}
浏览器访问Servlet显示图片
本质 就是 将一个文件的所有字节，复制到浏览器
src\com\wzx\pack05_download\Demo05Servlet.java
@WebServlet("/download")
public class Demo05Servlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.加载a.jpg文件成为一个输入流
InputStream inputStream = getServletContext().getResourceAsStream("download/a.mp3");
//2.再使用字节流 将数据写到浏览器
OutputStream outputStream = response.getOutputStream();
//3.浏览器自动将数据显示成图片
FileService fileService = new FileService();
fileService.copy(inputStream,outputStream);
//4.关闭
outputStream.close();
inputStream.close();
}
}
response-设置响应体-超链接访问文件
- (1）超链接访问图片
浏览器本身支持，本质也是先读文件，再将文件写到浏览器
web\index.html
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<a href="/web01_reponse/download/a.jpg">点一点看图片</a><br/>
<a href="/web01_reponse/download/a.mp3">点一点看mp3</a><br/>
<a href="/web01_reponse/download/a.mp4">点一点看mp4</a><br/>
<a href="/web01_reponse/download/a.zip">点一点看zip</a><br/>
</body>
</html>