关于java:JavaWeb学习笔记02-ServletCookieSession

Servlet

Servlet是sun公司开发的解决动静web的技术

Servlet有两个默认的实现类：HttpServlet、GenericServlet

开发Servlet程序的步骤：

编写一个类，实现Servlet接口
把开发好的Java类部署到web服务器中

实现了Servlet接口的java程序称为Servlet

创立HelloServlet我的项目

构建一个一般的maven我的项目，删除src文件夹，这个空的工程作为maven主工程

引入servlet jsp依赖到pom.xml

<dependencies>
  <!--增加Servlet和JSP依赖-->
  <dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>4.0.1</version>
  </dependency
  <!-- https://mvnrepository.com/artifact/javax.servlet.jsp/javax.servlet.jsp-api -->
  <dependency>
    <groupId>javax.servlet.jsp</groupId>
    <artifactId>javax.servlet.jsp-api</artifactId>
    <version>2.3.3</version>
  </dependency>
</dependencies>

或手动下载jar包到文件夹中

依赖下载地址:https://mvnrepository.com/

新建Module子模块servlet01（maven-archetype-webapp）

父我的项目中的java子项目能够间接应用，反之不能够

问题1:子项目pom中没有parent标签

解决：在子项目的pom.xml中手动增加parent标签并刷新maven

```
<parent>
  <groupId>cn.itxiaoma</groupId>
  <artifactId>HelloMaven</artifactId>
  <version>1.0-SNAPSHOT</version>
</parent>
```
问题2：子项目pom文件有一条横线并变灰

解决：file –>setting–>maven–>Ignored Files 将清单中对应我的项目的pom.xml文件勾销选中

将servlet01中的web.xml改为最新，在main目录下新建java和resources

<?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">
</web-app>

在java目录下新建package包cn..itxiaoma.servlet

在包下新建java类HelloServlet，并实现Servlet接口(继承HttpServlet)

package cn.itxiaoma.servlet;

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 HelloServlet extends HttpServlet {
    //get和post只是申请实现的不同形式，业务逻辑一样，因而能够相互调用
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        PrintWriter printWriter = resp.getWriter();
        printWriter.print("Hello Servlet");
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

编写Servlet的映射

浏览器连贯的是web服务，因而须要在web服务中注册咱们写的Servlet，并配置浏览器可能拜访的门路

<!--  注册Servlet-->
<servlet>
  <servlet-name>hello</servlet-name>
  <servlet-class>cn.itxiaoma.servlet.HelloServlet</servlet-class>
</servlet>
<!--  Servlet的申请门路-->
<servlet-mapping>
  <servlet-name>hello</servlet-name>
  <url-pattern>/hello</url-pattern>
</servlet-mapping>

配置Tomcat

Run > Edit Configurations > + > Tomcat Server – Local > Application server:抉择Tomcat目录

Deployment > + > servlet01:war exploed

Application Context: /servlet01_war_exploded
启动测试

http://localhost:8081/servlet…

Servlet原理
浏览器发送http申请(service)到web容器(Tomcat)
首次拜访的申请会加载Servlet类到内存
web容器生成申请(Request)和响应(Response)两个对象，并调用Servlet的service办法
Request会从service拿到申请，并执行咱们重写的解决办法，失去响应信息传给Response

web容器读取响应信息传回浏览器

Servlet Mapping问题

指定映射门路

<servlet-mapping>
  <servlet-name>hello</servlet-name>
  <url-pattern>/hello</url-pattern>
</servlet-mapping>

多映射门路

<servlet-mapping>
  <servlet-name>hello</servlet-name>
  <url-pattern>/hello/*</url-pattern>
</servlet-mapping>

默认申请门路(会笼罩首页)

<servlet-mapping>
  <servlet-name>hello</servlet-name>
  <url-pattern>/*</url-pattern>
</servlet-mapping>

指定后缀/前缀

<servlet-mapping>
  <servlet-name>hello</servlet-name>
  <url-pattern>*.test</url-pattern>
</servlet-mapping>

注：自定义后缀/前缀 * 前不能有映射门路

自定义异样解决ErrorServlet

cn/itxiaoma/servlet/ErrorServlet.java

package cn.itxiaoma.servlet;
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 ErrorServlet extends HttpServlet {
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     resp.setContentType("text/html");
     resp.setCharacterEncoding("utf-8");
     PrintWriter pw = resp.getWriter();
     pw.print("<h1>404</h1>");
 }
 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     doGet(req, resp);
 }
}

src/main/webapp/WEB-INF/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>cn.itxiaoma.servlet.HelloServlet</servlet-class>
  </servlet>
  <servlet-mapping>
 <servlet-name>hello</servlet-name>
 <url-pattern>/hello</url-pattern>
  </servlet-mapping>

  <servlet>
 <servlet-name>error</servlet-name>
 <servlet-class>cn.itxiaoma.servlet.ErrorServlet</servlet-class>
  </servlet>
  <servlet-mapping>
 <servlet-name>error</servlet-name>
 <url-pattern>/*</url-pattern>
  </servlet-mapping>
</web-app>

优先级问题：制订了固有的映射门路优先级最高，找不到再走默认的映射

ServletContext对象

web容器在启动的时候，它会为每个web程序创立一个ServletContext对象，代表以后的web利用

1. 共享数据

在一个Servlet中保留的数据，能够在其余Servlet中获取

web.xml

<servlet>
  <servlet-name>get</servlet-name>
  <servlet-class>cn.itxiaoma.servlet.GetServlet</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>get</servlet-name>
  <url-pattern>/get</url-pattern>
</servlet-mapping>

HelloServlet.java

package cn.itxiaoma.servlet;
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 HelloServlet extends HttpServlet {
 //get和post只是申请实现的不同形式，业务逻辑一样，因而能够相互调用
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     ServletContext context= this.getServletContext();
     String username = "Apple";
     context.setAttribute("username", username);
     System.out.println(username);
 }
 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     doGet(req, resp);
 }
}

GetServlet.java

package cn.itxiaoma.servlet;
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 GetServlet extends HttpServlet {
 //get和post只是申请实现的不同形式，业务逻辑一样，因而能够相互调用
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     ServletContext context = this.getServletContext();
     PrintWriter printWriter = resp.getWriter();
     resp.setContentType("text/html");
     resp.setCharacterEncoding("utf-8");
     printWriter.print("Username:" + context.getAttribute("username"));
 }
 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     doGet(req, resp);
 }
}

2. 获取初始化参数

web.xml

<context-param>
  <param-name>url</param-name>
  <param-value>jdbc:mysql://localhost:3306/testdb</param-value>
</context-param>

HelloServlet.java

package cn.itxiaoma.servlet;
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 HelloServlet extends HttpServlet {
 //get和post只是申请实现的不同形式，业务逻辑一样，因而能够相互调用
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     ServletContext context= this.getServletContext();
     String url = context.getInitParameter("url");
     resp.getWriter().print(url);
 }
 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     doGet(req, resp);
 }
}

3. 申请转发

ServletContext context= this.getServletContext();
RequestDispatcher requestDispatcher = context.getRequestDispatcher("/gp");//转发的申请门路
requestDispatcher.forward(req, resp);

4. 读取资源文件

resources文件夹下新建db.properties（会打包到classes门路下，称为classpath）

username=root
password=123456

读取资源文件

ServletContext context= this.getServletContext();
InputStream inputStream = context.getResourceAsStream("/WEB-INF/classes/db.properties");
Properties properties = new Properties();
properties.load(inputStream);
String username = properties.getProperty("username");
String password = properties.getProperty("password");
resp.getWriter().print(username + password);

HttpServletResponse

web服务器接管到客户端的http申请，针对这个申请，分表创立一个代表申请的HttpServletRequest对象，和一个代表响应的HttpServletResponse对象

javax/servlet/ServletResponse.java

负责向浏览器发送数据的办法

public ServletOutputStream getOutputStream() throws IOException;
public PrintWriter getWriter() throws IOException;

负责向浏览器发送响应头的办法

public void setCharacterEncoding(String charset);
public void setContentLength(int len);
public void setContentLengthLong(long len);
public void setContentType(String type);

常见利用

向浏览器输入音讯

下载文件

获取下载文件门路，文件名
获取下载文件的输出流
创立缓冲区
获取OutputStream对象
将FileOutputStream流写入Buffer缓冲区
应用OutputStream将缓冲区中的数据输入到客户端

String realPath = "/Users/4wheels/Downloads/test.jpg";
String filename = realPath.substring(realPath.lastIndexOf("/") + 1);
resp.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(filename, "UTF-8"));
//获取文件输出流
FileInputStream inputStream = new FileInputStream(realPath);
//缓冲区
int len = 0;
byte[] buffer = new byte[1024];
ServletOutputStream servletOutputStream = resp.getOutputStream();
while ((len = inputStream.read(buffer)) > 0) {
    servletOutputStream.write(buffer, 0, len);
}
inputStream.close();
servletOutputStream.close();

验证码性能

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    //浏览器3秒主动刷新
    resp.setHeader("refresh", "3");
    //在内存中创立图片
    BufferedImage image = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);
    //绘制图片
    Graphics2D g = (Graphics2D) image.getGraphics();
    g.setColor(Color.white);
    g.fillRect(0, 0, 80, 20);//绘制填色矩形
    g.setColor(Color.BLACK);
    g.setFont(new Font(null, Font.BOLD, 20));
    g.drawString(makeNum(), 2, 20);
    resp.setContentType("image/jpeg");
    resp.setDateHeader("expires", -1);//浏览器不缓存
    resp.setHeader("Cache-COntrol", "no-cache");
    resp.setHeader("Pragma", "no-cache");
    ImageIO.write(image, "jpg", resp.getOutputStream());
}

private String makeNum() {
    Random random = new Random();
    String num = random.nextInt(9999999) + "";
    StringBuffer sb = new StringBuffer();
    for (int i = 0; i < 7 - num.length(); i++) {
        sb.append("0");
    }
    num = sb.toString() + num;
    return num;
}

重定向

resp.sendRedirect("/test");

HttpServletRequest

解决登录申请

<html>
<body>
<form action="${pageContext.request.contextPath}/login" method="post">
 Username<input type="text" name="username"/><br>
 Password<input type="password" name="password"/><br>
 Hobby<input type="checkbox" name="hobby" value="1"/>
 <input type="checkbox" name="hobby" value="2"/>
 <input type="checkbox" name="hobby" value="3"/>
 <input type="submit"/>
</form>
</body>
</html>

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>login</servlet-name>
 <servlet-class>cn.itxiaoma.servlet.LoginServlet</servlet-class>
  </servlet>
  <servlet-mapping>
 <servlet-name>login</servlet-name>
 <url-pattern>/login</url-pattern>
  </servlet-mapping>
</web-app>

LoginServlet.java

package cn.itxiaoma.servlet;
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.util.Arrays;
public class LoginServlet extends HttpServlet {
 //get和post只是申请实现的不同形式，业务逻辑一样，因而能够相互调用
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     req.setCharacterEncoding("utf-8");
     resp.setCharacterEncoding("utf-8");
     String username = req.getParameter("username");
     String password = req.getParameter("password");
     String[] hobby = req.getParameterValues("hobby");
     System.out.println(username);
     System.out.println(password);
     System.out.println(Arrays.toString(hobby));
//        req.getRequestDispatcher("/success.jsp").forward(req, resp);
 }
 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     doGet(req, resp);
 }
}

Cookie

cookie只能保留字符串，不能保留对象
一个cookie只能保留一个信息，最大4kb
一个web站点能够给浏览器发送多个cookie，一个站点最多20个
浏览器最多存300个左右cookie

cookie不设置有效期或设为0，敞开浏览器主动生效

req.setCharacterEncoding("utf-8");
resp.setCharacterEncoding("utf-8");
resp.setContentType("text/html;charset=utf-8");
PrintWriter printWriter = resp.getWriter();
Cookie[] cookies = req.getCookies();
if (cookies != null) {
 printWriter.print("Last Time:");
 for (int i = 0; i < cookies.length; i++) {
     Cookie cookie = cookies[i];
     if (cookie.getName().equals("lastLoginTime")) {
         long lastLoginTime = Long.parseLong(cookie.getValue());
         Date date = new Date(lastLoginTime);
         printWriter.write(date.toLocaleString());
     }
 }
} else {
 printWriter.print("First Visit.");
}
Cookie cookie = new Cookie("lastLoginTime", System.currentTimeMillis()+"");
resp.addCookie(cookie);

Session

服务器会给每个用户（浏览器）创立一个Session，只有浏览器没有敞开，session就存在

Session和Cookie的区别：Cookie由客户端创立在浏览器保留，Session在服务器端创立和保留

Session和ServletContext区别：ServletContext作用域是全局（Web利用），Session作用域是会话（浏览器）

<servlet>
  <servlet-name>setSession</servlet-name>
  <servlet-class>cn.itxiaoma.servlet.SetSession</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>setSession</servlet-name>
  <url-pattern>/set</url-pattern>
</servlet-mapping>
<servlet>
  <servlet-name>getSession</servlet-name>
  <servlet-class>cn.itxiaoma.servlet.GetSession</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>getSession</servlet-name>
  <url-pattern>/get</url-pattern>
</servlet-mapping>
<servlet>
  <servlet-name>delSession</servlet-name>
  <servlet-class>cn.itxiaoma.servlet.DelSession</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>delSession</servlet-name>
  <url-pattern>/del</url-pattern>
</servlet-mapping>
<!--  设置session默认生效工夫-->
<session-config>
  <!-- 15分钟后主动生效-->
  <session-timeout>15</session-timeout>
</session-config>

SetSession.java

req.setCharacterEncoding("utf-8");
resp.setCharacterEncoding("utf-8");
resp.setContentType("text/html;charset=utf-8");
PrintWriter printWriter = resp.getWriter();
HttpSession session = req.getSession();
session.setAttribute("name", "test");
String sessionId = session.getId();
if (session.isNew()) {
 printWriter.write("Session创立胜利，Id：" + sessionId);
} else {
 printWriter.write("Session已存在，Id：" + sessionId);
}

GetSession.java

req.setCharacterEncoding("utf-8");
resp.setCharacterEncoding("utf-8");
resp.setContentType("text/html;charset=utf-8");
PrintWriter printWriter = resp.getWriter();
HttpSession session = req.getSession();
String sessionId = session.getId();
String sessionName = (String) session.getAttribute("name");
printWriter.write("Session Id:" + sessionId);
printWriter.write("Session Name:" + sessionName);

DelSession.java

HttpSession session = req.getSession();
//删除指定session
session.removeAttribute("name");
//手动登记session

关于java:JavaWeb学习笔记02-ServletCookieSession

Servlet

创立HelloServlet我的项目

Servlet原理

Servlet Mapping问题

自定义异样解决ErrorServlet

ServletContext对象

1. 共享数据

2. 获取初始化参数

3. 申请转发

4. 读取资源文件

HttpServletResponse

负责向浏览器发送数据的办法

负责向浏览器发送响应头的办法

常见利用

HttpServletRequest

解决登录申请

Cookie

Session

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关于java:JavaWeb学习笔记02-ServletCookieSession

Servlet

创立HelloServlet我的项目

Servlet原理

Servlet Mapping问题

自定义异样解决ErrorServlet

ServletContext对象

1. 共享数据

2. 获取初始化参数

3. 申请转发

4. 读取资源文件

HttpServletResponse

负责向浏览器发送数据的办法

负责向浏览器发送响应头的办法

常见利用

HttpServletRequest

解决登录申请

Cookie

Session

评论

发表回复 取消回复

更多文章

DDN HPC 存储硬件架构设计深度分析

探秘IO500：从Lustre并行文件系统出发，开启HPC存储性能新征程

苹果iOS打包的ipa应用无法安装？一篇文章带你了解可能的原因及排查方法

图解Golang：从零开始实现简易版过期LRU缓存

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