JavaWeb

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

转发

  • 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

  • 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