[学习笔记]马士兵 Servlet & JSP(1.Servlet)

1.HTTP协议基础测试（获取页面源代码）

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;

/**
 * HTTP协议基础测试
 * 本程序将Tomcat首页的页面源代码拿下来
 * 用此方法，我们可以将我们访问到的页面的内容都拿下来
 * @author ykn
 *
 */
public class HttpTest {

    public static void main(String[] args) {
       
        Socket s = null;
        PrintWriter pw = null;
        BufferedReader br = null;
           
        try {
            // 建立连接端口，s指向本地机器tomcat服务器端口上
            s = new Socket("127.0.0.1",8888);
            // 对于本程序而言是输出，则相当于是准备向tomcat服务器端口写请求
            pw = new PrintWriter(new OutputStreamWriter(s.getOutputStream()));
            // 请求访问页面（此处等同于访问）   
            pw.println("GET / HTTP/1.1");
            pw.println("Host: ");
            pw.println("Content-Type:text/html");
            pw.println("");
            // 上一句表示请求内容结束
            pw.flush();
            // 上面这一段用于本程序向Tomcat服务器发出访问请求（get）
           
           
            // 服务器端作出响应，对于本程序而言是输入
            br = new BufferedReader(new InputStreamReader(s.getInputStream()));
            String str = "";
            // 将服务器端的响应信息打印输出（即将页面代码源文件中的内容输出）
            // 用此方法，我们可以将我们访问到的页面的内容都拿下来
            while((str = br.readLine()) != null) {
                System.out.println(str);
            }
           
        } catch (UnknownHostException e) {
            System.out.println("未知的主机异常。。。");
            e.printStackTrace();
        } catch (IOException e) {
            System.out.println("IO异常。。。");
            e.printStackTrace();
        } finally {
            try {
                if (br != null) {
                    br.close();
                    br = null;
                }
                if (pw != null) {
                    pw.close();
                    pw = null;
                }
                if (s != null) {
                    s.close();
                    s = null;
                }
            } catch (IOException e) {
                System.out.println("IO异常。。。");
                e.printStackTrace();
            }           
        }
    }

}

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2.最简单的servlet示例
说明：
①将HelloWorldServlet .class拷贝到test\WEB-INF\classes目录下（test是项目名）
②在web.xml中添加对应的servlet处理语句：
   
        HW
        HelloWorldServlet
   
   
        HW
        /abc
   
③在URL地址栏中以形式访问
④页面上显示结果：Hello World!

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 简单的servlet示例
 * @author jukey
 *
 */
public class HelloWorldServlet extends HttpServlet {

   
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=gb2312");
        PrintWriter out = response.getWriter();
        out.println("Hello World!");
    }
   
}

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3.Servlet的生命周期测试

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet的生命周期
 * @author jukey
 *
 */
public class TestLifeCycleServlet extends HttpServlet {

    // 处理请求
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("doGet");
    }

    // 实例化
    // 注意：构造方法不能有返回值类型，连void也不行（否则就变成普通方法了）
    public TestLifeCycleServlet() {
        System.out.println("constructed");
    }
   
    // 退出服务
    public void destroy() {
        System.out.println("destory");
    }

    // 初始化
    public void init() throws ServletException {
        System.out.println("init");
    }

}

/*
测试结果（在tomcat服务器控制台窗口）：
constructed
init
doGet
*/

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4.读取指定的参数

①Threeparams.htm

   
       
           
               
       
       
           
               
       
       
           
               
       
       
           
               
       
   

param1
param2
param3

②ThreeParams.java

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 读取指定的参数
 * @author jukey
 *
 */
public class ThreeParams extends HttpServlet {

    // 参数在传递过程中，在URL地址栏中显示出来
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=gb2312");
        PrintWriter pw = response.getWriter();
        pw.println(request.getParameter("param1"));
        pw.println("
");
        pw.println(request.getParameter("param2"));
        pw.println("
");
        pw.println(request.getParameter("param3"));
        pw.println("
");
    }

    // 参数在传递过程中，在URL地址栏中隐藏了
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("doPost");
        // 调用doGet方法
        doGet(request,response);
    }

}

----------------------------------------------------------------------------------------------------------------------------------

5.读取所有的参数

①Showparameters.htm

   
       
   
    A sample show parameters
   
       

            Item Number:

            Quantity:

            Price each:

            First Name:

            Last Name:

            Middle Initial:

           
            Shipping Address:

            Credit Card:

           
              Visa

              Master Card

              Amex

              Discover

              Java SmartCard

           
            Credit Card password:

            Repeat Credit Card password:


           
           
           
       

   

②ShowParameters.java

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 读取所有的参数
 * @author jukey
 *
 */
public class ShowParameters extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=gb2312");
        PrintWriter out = response.getWriter();
       
        String title = "Reading All Request Parameters";
        out.println("init");
        out.println(""
                + title
                + "\n" + "\n"
                + "

Parameter Name

Parameter Value(s)");                 // Returns an Enumeration of String objects containing the names of the parameters contained in this request.         Enumeration paramNames = request.getParameterNames();         // Tests if this enumeration contains more elements.         while(paramNames.hasMoreElements()) {             // Returns the next element of this enumeration if this enumeration object has at least one more element to provide.             String paraName = (String)paramNames.nextElement();             out.println("

" + paraName + "\n

");             // Returns an array of String objects containing all of the values the given request parameter has, or null if the parameter does not exist.             // 注意参数paraName（变量）不能加双引号，否则就是找参数名叫paraName的对应值了。             String[] paramValues = request.getParameterValues(paraName);             // 这个参数只有一个值             if(paramValues.length == 1) {                 String paramValue = paramValues[0];                 if(paramValue.length() == 0) {                     out.println("no value");                 } else {                     out.println(paramValue);                 }             }else {                 // 这个参数有好几条值                 out.println(" ");                 for(int i = 0; i < paramValues.length; i++) {                     out.println(" " + paramValues[i]);                 }                 out.println(" ");             }         }         out.println("

\n");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("doPost");
        doGet(request,response);
    }

}

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6.Cookies的设置和读取

①设置Cookie到客户端

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 设置Cookie到客户端
 * @author jukey
 *
 */
public class SetCookies extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 向客户端写入Cookie，共6个
        for(int i = 0; i < 3; i++) {
            // 3个没有设置时间的Cookie，属于本窗口及其子窗口
            Cookie cookie = new Cookie("Session-Cookie-" + i, "Cookie-Value-S" + i);
            response.addCookie(cookie);
            // 以下3个Cookie设置了时间（3600秒，1小时），属于文本，别的窗口也可以访问到这些Cookie
            cookie = new Cookie("Persistent-Cookie-" + i, "Cookie-Value-P" + i);
            cookie.setMaxAge(3600);
            response.addCookie(cookie);
        }
       
        response.setContentType("text/html;charset=gb2312");
        PrintWriter out = response.getWriter();
        String title = "Setting Cookies";
        out.println(""
                + "" + title + "
"
                + "There are six cookies associates with this page.
"
                + "to see them,visit the \n"
                + "ShowCookies servlet"
                + "");
    }

}

②读取客户端的Cookies

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 读取客户端的Cookies
 * @author jukey
 *
 */
public class ShowCookies extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       
        response.setContentType("text/html;charset=gb2312");
        PrintWriter pw = response.getWriter();
        String title = "Active Cookies";
        pw.println("init");
        pw.println(""
                + title
                + "\n" + "\n"
                + "\n" + "\n"
                        + "\n");
            }
        }
        pw.println("

Cookie Name	Cookie Value" + " ");                 // 读取客户端的所有Cookie         Cookie[] cookies = request.getCookies();         if(cookies != null) {             Cookie cookie;             for(int i = 0; i < cookies.length; i++) {                 cookie = cookies[i];                 pw.println("
" + cookie.getName() +"	" + cookie.getValue() +"

\n");
    }

}

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7.Session的测试

①演示Servlet API中的session管理机制（常用方法）

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * 演示Servlet API中的session管理机制（常用方法）
 * @author jukey
 *
 */
public class SessionInfoServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       
        // Returns the current session associated with this request, or if the request does not have a session, creates one.
        HttpSession mySession = request.getSession(true);
       
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        String title = "Session Info Servlet";
        out.println("");
        out.println("");
        out.println("");
        out.println("");
        out.println("");
        out.println("

Session Infomation

");
       
        // Returns true if the client does not yet know about the session or if the client chooses not to join the session.
        out.println("New Session:" + mySession.isNew() + "
");
        // Returns a string containing the unique identifier assigned to this session.
        out.println("Session Id:" + mySession.getId() + "
");
        // Returns the time when this session was created, measured in milliseconds since midnight January 1, 1970 GMT.
        out.println("Session Create Time:" + new Date(mySession.getCreationTime()) + "
");
        out.println("Session Last Access Time:" + new Date(mySession.getLastAccessedTime()) + "
");
       
        out.println("

Request Infomation

");
        // Returns the session ID specified by the client.
        out.println("Session Id From Request:" + request.getRequestedSessionId() + "
");
        // Checks whether the requested session ID came in as a cookie.
        out.println("Session Id Via Cookie:" + request.isRequestedSessionIdFromCookie() + "
");
        // Checks whether the requested session ID came in as part of the request URL.
        out.println("Session Id Via URL:" + request.isRequestedSessionIdFromURL() + "
");
        // Checks whether the requested session ID is still valid.
        out.println("Valid Session Id:" + request.isRequestedSessionIdValid() + "
");
       
        out.println("refresh");
        out.println("");
        out.close();
    }

}

②Session追踪

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * Session追踪
 * 如果浏览器支持Cookie，创建Session的时候会把SessionId保存在Cookie中
 * 否则必须自己编程使用URL重写的方式实现Session：response.encodeURL()
 * @author jukey
 *
 */

public class ShowSession extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       
        response.setContentType("text/html;charset=gb2312");
        PrintWriter out = response.getWriter();
        String str = "Session Tracking Example";
        String heading;
       
        // 如果会话已经存在，则返回一个HttpSession；否则创建一个新的
        HttpSession session = request.getSession(true);
        // 从当前session中读取属性accessCount的值
        Integer accessCount = (Integer)session.getAttribute("accessCount");
        if(accessCount == null) {
            accessCount = new Integer(0);
            heading = "Welcome newUser";
        } else {
            heading = "Welcome Back";
            accessCount = new Integer(accessCount.intValue() + 1);
        }
        // 向当前session中插入键（key，属性）值（value）对
        // Binds an object to this session, using the name specified.
        session.setAttribute("accessCount", accessCount);
       
        out.println(""
                + "" + heading + "
"
                + "

Information on Your Session

"
                + "\n" + "\n"
                + "\n" + "\n"
                + "\n"
                + "\n" + "\n"
                + "\n"
                + "\n" + "\n"
                + "\n"
                + "\n" + "\n"
                + "\n"
                + "");
    }

}

--------------------------------------------------------------------------------------------------------------------------------

8.Application测试

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Application测试
 * 用于保存整个web应用的生命周期内都可以访问的数据
 * 可供多个不同窗口访问，可作为某一页面被总共访问次数的计数器（比如网站首页的访问量）
 * @author jukey
 *
 */
public class TestServletContext extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       
        response.setContentType("text/html;charset=gb2312");
        PrintWriter out = response.getWriter();
       
        // Returns a reference to the ServletContext in which this servlet is running.
        ServletContext application = this.getServletContext();
        // 从当前application中读取属性accessCount的值
        Integer accessCount = (Integer)application.getAttribute("accessCount");
        if(accessCount == null) {
            accessCount = new Integer(0);
        } else {
            accessCount = new Integer(accessCount.intValue() + 1);
        }
        // 向当前application中插入键（key，属性）值（value）对
        application.setAttribute("accessCount", accessCount);
       
        out.println("
"
                + "

\n"
                + "");
       
    }

}

---------------------------------------------------------------------------------------------------------------------------------------------

9.Servlet类本身位于包中的情况

package com.bjsxt.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet类本身位于包中的情况
 * classes中要class文件及其各级目录一起放置
 * web中如下设置：com.bjsxt.servlet.HelloWorldServlet2
 * @author jukey
 *
 */
public class HelloWorldServlet2 extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       
        response.setContentType("text/html;charset=gb2312");
        PrintWriter out = response.getWriter();
        out.println("Hello World!");
       
    }

}

--------------------------------------------------------------------------------------------------------------------------------

10.在Servlet中直接连接数据库，并查询显示信息

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 在Servlet中直接连接数据库，并查询显示信息
 * 每个application都应该有自己的驱动包，放在各自项目的WEB-INF\lib\目录下
 * @author jukey
 *
 */
public class ShowRs extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
       
        response.setContentType("text/html;charset=gb2312");
        PrintWriter out = response.getWriter();
        out.println("

Info Type	Value" + " "                 + "
ID	" + session.getId() +"
CreatTime	" + new Date(session.getCreationTime()) +"
LastAccessTime	" + new Date(session.getLastAccessedTime()) +"
Number of Access	" + accessCount +"
" + accessCount +"

");
        out.println("");

        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection("jdbc:mysql://localhost/bbs?user=root&password=mysql");
            stmt = conn.createStatement();
            String sql = "select * from article";
            rs = stmt.executeQuery(sql);
            while(rs.next()) {
                out.println("

");
                out.println("");
                out.println("");
            }
        } catch (SQLException ex) {
            ex.printStackTrace();
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
             if (rs != null) {
                 try {
                     rs.close();
                     rs = null;
                 } catch (SQLException sqlEx) {
                     sqlEx.printStackTrace();
                 }
             }
             if (stmt != null) {
                 try {
                     stmt.close();
                     stmt = null;
                 } catch (SQLException sqlEx) {
                     sqlEx.printStackTrace();
                 }
             }
             if (conn != null) {
                 try {
                     conn.close();
                     conn = null;
                 } catch (SQLException sqlEx) {
                     sqlEx.printStackTrace();
                 }
             }
        }
    }

}

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11.Servlet中使用专门的数据库操作类DB

①Servlet中使用专门的数据库操作类DB，这样，本程序就比前一个显得简单清楚

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet中使用专门的数据库操作类DB，这样，本程序就比前一个显得简单清楚
 * DB类，专门跟数据库打交道，分工明确，各司其职
 * @author jukey
 *
 */
public class ShowRsUseBean extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       
        response.setContentType("text/html;charset=gb2312");
        PrintWriter out = response.getWriter();
        out.println("

Content:

" + rs.getString("cont") + "

");
        out.println("");
       
        // 直接调用DB中的静态方法来为本类服务
        Connection conn = DB.getConnection();
        Statement stmt = DB.getStatement(conn);
        String sql = "select * from article";
        ResultSet rs = DB.getResultSet(stmt, sql);
       
        try {
            while(rs.next()) {
                out.println("");
                out.println("");
                out.println("");
            }
        } catch (SQLException e) {
            System.out.println("执行SQL遍历过程中出现了错误。。。");
            e.printStackTrace();
        } finally {
            // 直接调用DB中的静态方法来关闭一系列被打开的资源
            DB.close(rs);
            DB.close(stmt);
            DB.close(conn);
        }
    }

}

②专门跟数据库打交道的类

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * 专门跟数据库打交道的类
 * @author ykn
 *
 */
public class DB {

    // 获取连接
    public static Connection getConnection() {
        Connection conn = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection("jdbc:mysql://localhost/bbs?user=root&password=mysql");
        } catch (ClassNotFoundException e) {
            System.out.println("驱动程序未找到，请加入mysql.jdbc的驱动包。。。");
            e.printStackTrace();
        } catch (SQLException e) {
            System.out.println("执行数据库连接过程中出现了错误。。。");
            e.printStackTrace();
        }
        return conn;
    }
   
    // 获取表达式语句
    public static Statement getStatement(Connection conn) {
        Statement stmt = null;
        try {
            if (conn != null) {
                stmt = conn.createStatement();
            }
        } catch (SQLException e) {
            System.out.println("执行获取表达式语句过程中出现了错误。。。");
            e.printStackTrace();
        }       
        return stmt;
    }
   
    // 获取查询的结果集
    public static ResultSet getResultSet(Statement stmt, String sql) {
        ResultSet rs = null;
        try {
            if (stmt != null) {
                rs = stmt.executeQuery(sql);
            }
        } catch (SQLException e) {
            System.out.println("执行查询过程中出现了错误。。。");
            e.printStackTrace();
        }
        return rs;
    }
   
    // 关闭连接
    public static void close(Connection conn) {
        try {
            if (conn != null) {
                conn.close();
                conn = null;
            }
        } catch (SQLException e) {
            System.out.println("执行关闭数据库连接过程中出现了错误。。。");
            e.printStackTrace();
        }       
    }
   
    // 关闭表达式语句
    public static void close(Statement stmt) {
        try {
            if (stmt != null) {
                stmt.close();
                stmt = null;
            }
        } catch (SQLException e) {
            System.out.println("执行关闭表达式语句过程中出现了错误。。。");
            e.printStackTrace();
        }       
    }
   
    // 关闭结果集
    public static void close(ResultSet rs) {
        try {
            if (rs != null) {
                rs.close();
                rs = null;
            }
        } catch (SQLException e) {
            System.out.println("执行关闭结果集过程中出现了错误。。。");
            e.printStackTrace();
        }       
    }
}

 

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Content:

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