JavaWeb

Servlet

实现了Servlet接口的java程序叫做Servlet

引入Servlet包

<dependencies>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.2</version>
        </dependency>
    </dependencies>

新建moudle修改web.xml头信息

<?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">
</web-app>

helloServlet

编写代码

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 {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        PrintWriter writer = resp.getWriter ();
        writer.print ("hello,y4er");

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }


}

编写Servlet映射（web.xml中）

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

运行测试

ServletContext

this.getInitParameter() 初始化参数
this.getServletConfig() Servlet配置
this.getServletContext() Servlet上下文

共享数据

helloservlet

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 {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext ();

        String user = "syst1m";

        servletContext.setAttribute ("username",user);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }


}

replyservlet

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 replyservlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext ();
        String username = (String) servletContext.getAttribute ("username");

        resp.setContentType ("text/html");
        resp.setCharacterEncoding ("utf-8");
        resp.getWriter ().print ("名字为"+username);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet (req, resp);
    }
}

注册Servlet

 <servlet>
    <servlet-name>hello</servlet-name>
    <servlet-class>helloservlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello</url-pattern>
  </servlet-mapping>
  <servlet>
    <servlet-name>reply</servlet-name>
    <servlet-class>replyservlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>reply</servlet-name>
    <url-pattern>/reply</url-pattern>
  </servlet-mapping>

运行测试

获得初始化参数

注册Servlet

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

 <servlet>
    <servlet-name>jdbc</servlet-name>
    <servlet-class>jdbcServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>jdbc</servlet-name>
    <url-pattern>/jdbc</url-pattern>
  </servlet-mapping>

代码

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 jdbcServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext ();
        String url = servletContext.getInitParameter ("jdbc");
        resp.getWriter ().print (url);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost (req, resp);
    }
}

运行测试

code

public class forward extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext ();
        servletContext.getRequestDispatcher ("/jdbc").forward (req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost (req, resp);
    }
}

读取资源文件

db.properties

username=syst1m
password=123456

code

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.InputStream;
import java.util.Properties;

public class jdbcServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        InputStream is = this.getServletContext ().getResourceAsStream ("WEB-INF/classes/db.properties");

        Properties prop = new Properties ();
        prop.load (is);
        String username = prop.getProperty ("username");
        String password = prop.getProperty ("password");

        resp.getWriter ().print (username+password);

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost (req, resp);
    }
}

运行测试

HttpServletResponse

Response下载文件

code

public class FileServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取下载文件的路径
        String realPath = "/Users/syst1m/code/chabugservlet/com.web.servlet/src/main/resources/1.png";
        String FileName = realPath.substring (realPath.lastIndexOf ("\")+1);
        resp.setHeader ("Content-Disposition","attachment;filename="+ URLEncoder.encode (FileName,"UTF-8"));
        FileInputStream in = new FileInputStream (realPath);
        int len = 0;
        byte[] buffer = new byte[1024];
        ServletOutputStream out = resp.getOutputStream ();
        while((len=in.read(buffer))>0){
            out.write (buffer,0,len);
        }

        in.close();
        out.close ();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

注册Servlet

</servlet-mapping>
  <servlet>
    <servlet-name>down</servlet-name>
    <servlet-class>FileServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>down</servlet-name>
    <url-pattern>/down</url-pattern>
  </servlet-mapping>

运行测试

Response实现验证码

code

public class captchaServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //浏览器每三秒刷新一次
        resp.setHeader ("refresh","3");
        //内存中创建一张图片
        BufferedImage image = new BufferedImage (80,20,BufferedImage.TYPE_3BYTE_BGR);
        //得到图片
        Graphics2D g = (Graphics2D)image.getGraphics ();
        //设置图片背景色
        g.setColor (Color.white);
        g.fillRect (0,0,80,80);
        //给图片写数据
        g.setColor (Color.blue);
        g.setFont (new Font (null,Font.BOLD,20));
        g.drawString (makenum(),1,20);
        //浏览器：以图片类型打开
        resp.setContentType ("image/jpeg");
        //清除缓存，不让浏览器缓存
        resp.setDateHeader ("expires",-1);
        resp.setHeader ("Cache-Control","no-cache");
        resp.setHeader ("Pragme","no-cache");
        // 把图片写给浏览器
        ImageIO.write (image,"jpg",resp.getOutputStream ());

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
    //生成随机数

    private String makenum(){
        Random random = new Random ();
        String num = random.nextInt (9999)+"";
        StringBuffer sb = new StringBuffer ();

        for (int i = 0; i < 7-num.length (); i++) {
            sb.append ("0");
        }
        num = sb.toString ()+num;
        return num;
    }
}

注册Servlet

<servlet>
    <servlet-name>img</servlet-name>
    <servlet-class>captchaServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>img</servlet-name>
    <url-pattern>/img</url-pattern>
  </servlet-mapping>

运行测试

Response实现重定向

resp.sendRedirect

HttpServletRequest

注册Servlet

 <servlet>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>LoginServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/login</url-pattern>
  </servlet-mapping>

index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登陆</title>
</head>
<body>
<h1>登陆</h1>
    <div>
        <form action="${pageContext.request.contextPath}/login" method="post">

            用户名：<input type="text" name="username"><br>
            密码：<input type="password" name="password"><br>
            爱好：
            <input type="checkbox" name="hobbys" value="女孩">女孩
            <input type="checkbox" name="hobbys" value="代码">代码
            <input type="checkbox" name="hobbys" value="chabug">chabug
            <input type="checkbox" name="hobbys" value="渗透测试">渗透测试

            <br>
            <button type="submit">submit</button>
        </form>
    </div>
</body>
</html>

success.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登陆成功</title>
</head>
<body>
<h1>登陆成功</h1>
</body>
</html>

LoginServlet

public class LoginServlet extends HttpServlet {

    @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[] hobbys = req.getParameterValues ("hobbys");

       System.out.println (username);
       System.out.println (password);
       System.out.println (Arrays.toString (hobbys));
       req.getRequestDispatcher ("/success.jsp").forward (req,resp);


    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

运行测试

Cookie

注册Servlet

  <servlet>
    <servlet-name>cookie</servlet-name>
    <servlet-class>CookieServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>cookie</servlet-name>
    <url-pattern>/cookie</url-pattern>
  </servlet-mapping>
</web-app>

code

public class CookieServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //解决乱码

        req.setCharacterEncoding ("UTF-8");
        resp.setCharacterEncoding ("UTF-8");
        PrintWriter out = resp.getWriter ();
        Cookie[] cookies = req.getCookies ();

        if(cookies!=null){
            out.write ("你上一次的时间是");
            for (int i = 0; i < cookies.length; i++) {
                Cookie cookie = cookies[i];
                if(cookie.getName ().equals ("lastlogintime")){
                    long logintime = Long.parseLong (cookie.getValue ());
                    Date date = new Date (logintime);
                    out.write (date.toLocaleString ());
                }
            }
        }else {
            out.write ("这是你第一次访问本站点");
        }
        Cookie cookie = new Cookie ("lastlogintime",System.currentTimeMillis ()+"");
        cookie.setMaxAge (***);
        resp.addCookie (cookie);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

运行测试

Session

设置，读取，删除

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取Sesseion对象
        HttpSession session=request.getSession();
        session.setAttribute("username", "zhangsan");//存储数据
        session.getAttribute("username");//获取数据
        session.removeAttribute("username");//删除数据
    }

Session的销毁

session.invalidate()

JSP

jsp原理

内置对象

final javax.servlet.jsp.PageContext pageContext; 页面上下文
javax.servlet.http.HttpSession session1 = null; session
final javax.servlet.ServletContext application; applicationContext
final javax.servlet.ServletConfig config; config
javax.servlet.jsp.JspWriter out = null; out 
final java.lang.Object page = this; page 当前
HttpServletRequest request  请求
HttpServletResponse response 响应

maven依赖

JSTL表达式依赖

<dependency>
    <groupId>javax.servlet.jsp.jstl</groupId>
    <artifactId>jstl-api</artifactId>
    <version>1.2</version>
</dependency>

standard标签库

<dependency>
    <groupId>taglibs</groupId>
    <artifactId>standard</artifactId>
    <version>1.1.2</version>
</dependency>

JSP基础语法和指令

Tomcat热部署

https://blog.csdn.net/jc0803kevin/article/details/88579109

Jsp表达式

<%--jsp表达式，用来将程序的输出，输出到客户端--%>
<%--<%= 变量或表达式%>--%>
<%= new java.util.Date()%>

jsp脚本片段

<%

    int sum = 0;
    for (int i = 0; i < 100; i++) {
        sum+=1;
    }

    out.println ("<h1>sum="+sum+"</h1>");
%>

jso声明

<%!

    static {
        System.out.println ("Loading Servlet");
    }

    private int globalVar = 0;

    public void test(){
        System.out.println ("进入了方法test");
    }
%>

jsp声明会被编译到JSP生成的java的类中，其他的会被生成到_jspServlet方法中

JSP指令

定制错误页面

<%@page args...%>

<%@page errorPage="err/err.html" %>

文件包含

<%@include file="index.jsp"%>
<jsp:include page="index.jsp">

JSP内置对象及作用域

9大内置对象

PageContext  存东西
Request  存东西
Response
Session
Application  [ServletContext] 存东西
config  [ServletConfig]
out
page
exception

code

 pageContext.setAttribute("name1","syst1m1");  //一个页面中有效
 request.setAttribute("name2","syst1m2"); //一个请求中有效
 session.setAttribute("name3"."syst1m3"); //一个会话中有效
 application.setAttribute("name4"."syst1m4"); //保存的数据在服务器中中有效

通过寻找的方式获取

pageContext.findAttribute();

重定向

pageContext.forward()

Jsp、JSTL标签、EL表达式

EL表达式

el表达式 ${}

获取数据

${标识符}

执行运算
获取web开发的常用对象

jsp标签

<jsp:forward page="test.jsp">
    <jsp:param name="paramtest" value="test"/>
</jsp:forward>

JSTL表达式

核心标签

引入JSTL核心标签库

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

set标签：将值保存在指定的作用域中

<%-- var="变量名"  value="值" scope="保存在哪个作用域（page、request、session、application）"--%>
<c:set var="userName" value="yzq" scope="page"></c:set>
<span>${userName}</span><%--配合EL表达式取值--%>

out标签：将结果输出

<%--取值--%>
<c:out value="${userName}"></c:out>

if标签：判断

<c:if test="${age>20}">

    <span>奔三的人了</span>

</c:if>

choose：选择，跟java中的switch语句类似

<c:set var="age" scope="page" value="40"></c:set>
<c:choose>

    <%--符合该条件时执行--%>
    <c:when test="${age>20&&age<30}">
        <span>奔三的人了</span>
    </c:when>

    <%--符合该条件时执行--%>
    <c:when test="${age<20}">
        <span>还是小鲜肉</span>

    </c:when>

    <%--之前条件都不满足时，执行这个--%>
    <c:otherwise>

        <span>可以考虑养生了</span>

    </c:otherwise>
</c:choose>

forEach标签：用于迭代集合

<%--迭代标签 用于迭代集合--%>
<c:forEach items="${users}" var="user">

    <span>${user.name}</span>:<span>${user.age}</span>
    <br>

</c:forEach>

JavaBean

一般用来与数据库的字段做映射

code

javabean.java

package com.bean.pojo;

public class People {

    private int id;
    private String name;
    private int age;
    private String address;

    public People() {
    }

    public People(int id, String name, int age, String address) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.address = address;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "People{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", age=" + age +
                ", address='" + address + ''' +
                '}';
    }
}

javabean.jsp

<jsp:useBean id="people" class="com.javabean.pojo.People" scope="page"/>
<jsp:setProperty name="people" property="address" value="北京"></jsp:setProperty>
<jsp:getProperty name="people" property="address"/>

过滤器Filter

编写Servlet

public class helloservlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         resp.getWriter ().write ("你好呀，世界");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

编写Filter

public class encodeing implements Filter {
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        servletRequest.setCharacterEncoding ("utf-8");
        servletResponse.setCharacterEncoding ("utf-8");
        servletResponse.setContentType ("text/html;charset=UTF-8");
        System.out.println ("过滤器执行前");
        filterChain.doFilter (servletRequest,servletResponse);
        System.out.println ("过滤器执行后");
    }

    public void destroy() {

    }
}

注册Filter

<filter>
    <filter-name>encode</filter-name>
    <filter-class>encodeing</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>encode</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

测试

监听器

统计在线人数Demo

index.jsp

<html>
<body>
<h2>Hello World!</h2>


<h1>当前有<span><%=this.getServletConfig().getServletContext().getAttribute("OnlineCount")%></span></h1>
</body>
</html>

OnlineCount

@Override
    public void sessionCreated(HttpSessionEvent httpSessionEvent) {
        ServletContext ctx = httpSessionEvent.getSession ().getServletContext ();
        Integer onlineCount = (Integer)ctx.getAttribute ("OnlineCount");

        if(onlineCount==null){
            onlineCount=new Integer (1);
        }else {
            int count= onlineCount.intValue ();
            onlineCount = new Integer (count+1);
        }
        ctx.setAttribute ("OnlineCount",onlineCount);
    }

    //销毁session监听
    @Override
    public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
        ServletContext ctx = httpSessionEvent.getSession ().getServletContext ();
        Integer onlineCount = (Integer)ctx.getAttribute ("OnlineCount");

        if(onlineCount==null){
            onlineCount=new Integer (0);
        }else {
            int count= onlineCount.intValue ();
            onlineCount = new Integer (count-1);
            httpSessionEvent.getSession ().invalidate ();
        }
        ctx.setAttribute ("OnlineCount",onlineCount);
    }

注册监听器

<listener>
    <listener-class>OnlineCount</listener-class>
</listener>

测试

JDBC(Java fatabase connect)

JDBC

package com.jdbc4;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Timestamp;
import java.util.Date;

public class TestUpdate {

  /**
   * @param args
   */
  public static void main(String[] args) {
    Connection conn=null;
    try {
      Class.forName("com.mysql.jdbc.Driver");
      //建立连接  ctrl+shfit +o
      conn=DriverManager.getConnection("jdbc:mysql://localhost/test?useUnicode=true&characterEncoding=utf-8", "root", "19810109");
      String sql="update book set title=?,price=?,birth=?,publish_date=?,update_date=? where id=?";
      //预编译
      PreparedStatement pstmt=conn.prepareStatement(sql);
      pstmt.setString(1, "四集");
      pstmt.setFloat(2, 50.55f);
      pstmt.setDate(3, new java.sql.Date(new Date().getTime()));
      pstmt.setTimestamp(4, new Timestamp(new Date().getTime()));
      pstmt.setTimestamp(5, new Timestamp(new Date().getTime()));
      pstmt.setInt(6, 1);

      //执行
      pstmt.executeUpdate();
    } catch (Exception e) {
      e.printStackTrace();
    }
    finally
    {
      try {
        conn.close();
      } catch (SQLException e) {
        e.printStackTrace();
      }
    }
  }

}

JDBC事务

connection.setAutoCommit(false) 开启事务

原创文章，作者：syst1m，未经授权禁止转载！如若转载，请联系作者：syst1m

Java学习入门之JavaWeb

JavaWeb

Servlet

helloServlet

ServletContext

共享数据

获得初始化参数

转发

读取资源文件

HttpServletResponse

Response下载文件

Response实现验证码

Response实现重定向

HttpServletRequest

Cookie

Session

JSP

JSP基础语法和指令

JSP指令

JSP内置对象及作用域

Jsp、JSTL标签、EL表达式

EL表达式

jsp标签

JSTL表达式

核心标签

JavaBean

code

过滤器Filter

监听器

统计在线人数Demo

JDBC(Java fatabase connect)

JDBC

JDBC事务

联系我们

Java学习入门之JavaWeb

JavaWeb

Servlet

helloServlet

ServletContext

共享数据

获得初始化参数

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统计在线人数Demo

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