javawebServlet
javaweb
http响应
服务器 -- 响应 -- 客户端
Accept：告诉浏览器它所支持的数据类型
Accept-Encoding：支持那种 编码格式 GBK UTF-8 GB2312 ISO8859-1
Content-Type：text/html 类型
Content-Type: image/png
Connection：keep-Alive 连接
Cache-Control： private 缓存控制
Content-Encoding：gzip 编码
Host：主机……/.
Refresh ：告诉客户端多久刷新一次
Location：让网页重新定位
servlet
web.xml
<?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"
metadata-complete="true">
<servlet>
<servlet-name>hello</servlet-name>
<servlet-class>day1.ServletDemo</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>
</web-app>
package day1;
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.io.PrintWriter;
public class ServletDemo extends HttpServlet
{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//ServletInputStream inputStream = req.getInputStream();
PrintWriter writer = resp.getWriter();
writer.println("hello world!");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req, resp);
}
}
<?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"
metadata-complete="true">
<!-- 注册servlet-->
<servlet>
<servlet-name>hello</servlet-name>
<servlet-class>day1.ServletDemo</servlet-class>
</servlet>
<!-- 可以有多个servlet映射-->
<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/hello1</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/hello2</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/hello3/*</url-pattern>
<!-- 映射可以使用统配符-->
</servlet-mapping>
</web-app>
<?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"
metadata-complete="true">
<!-- 注册servlet-->
<servlet>
<servlet-name>hello</servlet-name>
<servlet-class>day1.ServletDemo</servlet-class>
</servlet>
<!-- 可以有多个servlet映射-->
<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/hello1</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/hello2</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/hello3/*</url-pattern>
<!-- 映射可以使用统配符-->
</servlet-mapping>
<servlet>
<servlet-name>error</servlet-name>
<servlet-class>day1.ErrorServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>error</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
</web-app>
优先级问题，指定的固有的映射路径优先级最高，如果找不到就会走默认的处理请求
servlet使用
<?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"
metadata-complete="true">
<servlet>
<servlet-name>test</servlet-name>
<servlet-class>test.ContextTest</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>test</servlet-name>
<url-pattern>/test</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>test1</servlet-name>
<servlet-class>test.Test</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>test1</servlet-name>
<url-pattern>/test1</url-pattern>
</servlet-mapping>
</web-app>
package test;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class ContextTest extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req, resp);
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// this.getServletConfig()//获取servlet配置
//this.getInitParameter()//获得servlet初始化参数
ServletContext servletContext = this.getServletContext();
servletContext.setAttribute("username","王涛");
}
}
package test;
import javax.servlet.ServletContext;
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.io.PrintWriter;
public class Test extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req, resp);
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.setContentType("text/html");
resp.setCharacterEncoding("utf8");
PrintWriter writer = resp.getWriter();
ServletContext servletContext = this.getServletContext();
Object username = servletContext.getAttribute("username");
writer.println(username.toString());
writer.close();
}
}
文件过滤问题
<resources>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
</resources>
HttpServletRequest
获取前端传递参数
package com.test;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LoginServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String username = req.getParameter("username");
String password = req.getParameter("password");
String[] hobbys = req.getParameterValues("hobbys");
for (String hobby : hobbys) {
System.out.println(hobby);
}
req.getRequestDispatcher("/success.jsp").forward(req,resp);
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req, resp);
}
}
<h2>Hello World!</h2>
<div style="text-align: center;">
<form method="post" action="${pageContext.request.contextPath}/login">
username: <input type="text" name="username">
password: <input type="password" name="password">
hobby:
<input type="checkbox" name="hobbys" value="girl"> girl
<input name="hobbys" type="checkbox" value="encoding"> encoding
<input name="hobbys" type="checkbox" value="song"> song
<input type="checkbox" name="hobbys" value="playboy"> playboy
<br>
<input type="submit">
</form>
</div>
307
HttpServletResponse
响应
web服务器接受到客户端的http请求，针对这个请求，分别创建一个代表响应的HttpServletResponse对象，代表请求的HttpServletRequest对象，
请求来的信息找HttpServletRequest，响应回去的信息找HttpServletResponse
简单分类
负责向浏览器发送数据的方法
public ServletOutputStream getOutputStream() throws IOException;
public PrintWriter getWriter() throws IOException;
负责向浏览器发送响应头的方法
public void setCharacterEncoding(String charset);
public void setContentLength(int len);
public void setContentLengthLong(long len);
public void setContentType(String type);
public void setBufferSize(int size);
public int getBufferSize();
public void setDateHeader(String name, long date);
public void addDateHeader(String name, long date);
public void setHeader(String name, String value);
public void addHeader(String name, String value);
public void setIntHeader(String name, int value);
public void addIntHeader(String name, int value);
public void setStatus(int sc);
public static final int SC_CONTINUE = 100;
public static final int SC_SWITCHING_PROTOCOLS = 101;
public static final int SC_OK = 200;
public static final int SC_CREATED = 201;
public static final int SC_ACCEPTED = 202;
public static final int SC_NON_AUTHORITATIVE_INFORMATION = 203;
public static final int SC_NO_CONTENT = 204;
public static final int SC_RESET_CONTENT = 205;
public static final int SC_PARTIAL_CONTENT = 206;
public static final int SC_MULTIPLE_CHOICES = 300;
public static final int SC_MOVED_PERMANENTLY = 301;
public static final int SC_MOVED_TEMPORARILY = 302;
public static final int SC_FOUND = 302;
public static final int SC_SEE_OTHER = 303;
public static final int SC_NOT_MODIFIED = 304;
public static final int SC_USE_PROXY = 305;
public static final int SC_TEMPORARY_REDIRECT = 307;
public static final int SC_BAD_REQUEST = 400;
public static final int SC_UNAUTHORIZED = 401;
public static final int SC_PAYMENT_REQUIRED = 402;
public static final int SC_FORBIDDEN = 403;
public static final int SC_NOT_FOUND = 404;
public static final int SC_METHOD_NOT_ALLOWED = 405;
public static final int SC_NOT_ACCEPTABLE = 406;
public static final int SC_REQUEST_TIMEOUT = 408;
public static final int SC_CONFLICT = 409;
public static final int SC_GONE = 410;
public static final int SC_LENGTH_REQUIRED = 411;
public static final int SC_PRECONDITION_FAILED = 412;
public static final int SC_REQUEST_ENTITY_TOO_LARGE = 413;
public static final int SC_REQUEST_URI_TOO_LONG = 414;
public static final int SC_UNSUPPORTED_MEDIA_TYPE = 415;
public static final int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416;
public static final int SC_EXPECTATION_FAILED = 417;
public static final int SC_INTERNAL_SERVER_ERROR = 500;
public static final int SC_NOT_IMPLEMENTED = 501;
public static final int SC_BAD_GATEWAY = 502;
public static final int SC_SERVICE_UNAVAILABLE = 503;
public static final int SC_GATEWAY_TIMEOUT = 504;
public static final int SC_HTTP_VERSION_NOT_SUPPORTED = 505;
文件下载
package test;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;
public class DownServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//1.获取下载的文件路径
String realPath = "D:\\ideaProject\\MavenProject\\ServeltTest\\ContextTest\\src\\main\\resources\\1.png";
//D:\apache-tomcat-8.5.84\webapps\ContextTest_war\1.png,可以写死，直接写绝对路径
System.out.println(realPath);
//2.下载的文件名是什么？
String substring = realPath.substring(realPath.indexOf("\\") + 1);
//3.设置想办法让浏览器能够支持下载我们需要的资源
resp.setHeader("Content-Disposition","attachment;filename"+ URLEncoder.encode(substring,"utf-8"));
//4.获取下载文件的输入流
FileInputStream fileInputStream = new FileInputStream(realPath);
//5.创建缓冲区
byte[] bytes = new byte[1024];
int len;
//6.获取输出流对象
ServletOutputStream outputStream = resp.getOutputStream();
//7.文件输出流写入到缓冲区
while ((len = fileInputStream.read(bytes))!=-1){
outputStream.write(bytes);
}
//8.使用输出流讲缓冲区中的数据输入到客户端
outputStream.close();
fileInputStream.close();
}
}
验证码实现
package test;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
public class imageServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req, resp);
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//告诉浏览器每五秒刷新一次
resp.setHeader("refresh","5");
//在内存中创建图片
BufferedImage bufferedImage = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);
Graphics graphics = bufferedImage.getGraphics();//生成画笔工具
graphics.setColor(Color.white);//设置画笔颜色白色
graphics.fillRect(0,0,80,20);//画出一个矩形图片宽80高20再0,0位置
//生成随机数
graphics.setColor(Color.BLUE);//设置画笔颜色蓝色
graphics.setFont(new Font(null,Font.BOLD,20));//设置字体
graphics.drawString(makeInt(),0,20);//画出String
resp.setContentType("image/jpeg");//告诉浏览器响应类型
resp.setDateHeader("expires",-1);//告诉浏览器数据不缓存
resp.setHeader("Cache-Control","no-cache");//缓存控制，不缓存
resp.setHeader("Pragma","no-cache");
//使用ImageIO写出image对象
ImageIO.write(bufferedImage,"jpeg",resp.getOutputStream());
}
public String makeInt(){
Random random = new Random();
int i = random.nextInt(9999999);
String s = "" + i;
StringBuffer buffer = new StringBuffer();
for (int j = 0;j < 7-s.length();j++){
int nextInt = random.nextInt(10);
String s1 = nextInt + "";
buffer.append(s1);
}
s = buffer.toString() + s;
return s;
}
}
实现重定向
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.sendRedirect("/ContextTest_war/image");
}//重定向，实现请求转发
等价于
resp.setHeader("Location","/ContextTest_war/image");
resp.setStatus(302);
<html>
<body>
<h2>Hello World!</h2>
<form action="${pageContext.request.contextPath}/login" method="get">
<input type="text" name="username"> username
<input type="password" name="password"> password
<input type="submit">
</form>
</body>
</html>
package test;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LoginServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req, resp);
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("login");
resp.setHeader("Location","/ContextTest_war/image");
resp.setStatus(302);
System.out.println(req.getParameter("username"));
System.out.println(req.getParameter("password"));
}
}
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