马士兵 Servlet & JSP（1） Servlet (源代码)

2023-07-20 11:58:52

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http://localhost:8888/）

pw.println("GET / HTTP/1.1");

pw.println("Host: www.bjsxt.com");

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http://localhost:8888/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：

<servlet>

<servlet-name>HW</servlet-name>

<servlet-class>HelloWorldServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>HW</servlet-name>

<url-pattern>/abc</url-pattern>

</servlet-mapping>

③在URL地址栏中以http://localhost:8888/test/abc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

<form id="form1" name="form1" method="post" action="servlet/Threeparams">

<table width="343" border="1">

<tr>

<td width="92">param1</td>

<td width="94"><input name="param1" type="text" id="param1"/></td>

</tr>

<tr>

<td width="92">param2</td>

<td width="94"><input name="param2" type="text" id="param2"/></td>

</tr>

<tr>

<td width="92">param3</td>

<td width="94"><input name="param3" type="text" id="param3"/></td>

</tr>

<tr>

<td> </td>

<td><input type="submit" value="提交"/></td>

</tr>

</table>

</form>

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("<br>");

pw.println(request.getParameter("param2"));

pw.println("<br>");

pw.println(request.getParameter("param3"));

pw.println("<br>");

}

// 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);

}

}

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5.读取所有的参数

①Showparameters.htm

<html>

<head>

<title>A sample show parameters</title>

</head>

<body>A sample show parameters



<form method="post" action="servlet/ShowParameters">

Item Number:<input type="text" name="itemNum"><br>

Quantity:<input type="text" name="quantity"><br>

Price each:<input type="text" name="price" value="$"><br>

First Name:<input type="text" name="firstName"><br>

Last Name:<input type="text" name="lastName"><br>

Middle Initial:<input type="text" name="initial"><br>



Shipping Address:<textarea name="address" row="3" cols="40"></textarea><br>

Credit Card:<br>



  <input type="radio" name="cardType" value="Visa">Visa<br>

  <input type="radio" name="cardType" value="Master Card">Master Card<br>

  <input type="radio" name="cardType" value="Amex">Amex<br>

  <input type="radio" name="cardType" value="Discover">Discover<br>

  <input type="radio" name="cardType" value="Java SmartCard">Java SmartCard<br>



Credit Card password:<input type="password" name="cardNum"><br>

Repeat Credit Card password:<input type="password" name="cardNum"><br><br>



<center><input type="submit" value="Submit Order"></center>



</form>

</body>

</html>

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("<html><head><title>读取所有参数</title></head>"

+ title

+ "/n" + "<table border=1 align=center>/n"

+ "<TH>Parameter Name<TH>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("<tr><td>" + paraName + "/n<td>");

// 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("<I>no value</I>");

} else {

out.println(paramValue);

}

}else {

// 这个参数有好几条值

out.println("<UL>");

for(int i = 0; i < paramValues.length; i++) {

out.println("<LI>" + paramValues[i]);

}

out.println("</UL>");

}

}

out.println("</table>/n<body><html>");

}

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("<html><head><title>设置Cookie</title></head>"

+ "<body>" + title + "<br>"

+ "There are six cookies associates with this page.<br>"

+ "to see them,visit the <a href=/"ShowCookies/">/n"

+ "<code>ShowCookies</code> servlet</a>"

+ "</body></html>");

}

}

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("<html><head><title>读取客户端</title></head>"

+ title

+ "/n" + "<table border=1 align=center>/n"

+ "<TH>Cookie Name<TH>Cookie Value" + "<br>");



// 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("<tr>/n" + "<td>" + cookie.getName() +"</td>/n"

+ "<td>" + cookie.getValue() +"</td></tr>/n");

}

}

pw.println("</table>/n<body><html>");

}

}

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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("<html>");

out.println("<head>");

out.println("<title>Session Info Servlet</title>");

out.println("</head>");

out.println("<body>");

out.println("<h3>Session Infomation</h3>");



// 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() + "<br>");

// Returns a string containing the unique identifier assigned to this session.

out.println("Session Id:" + mySession.getId() + "<br>");

// 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()) + "<br>");

out.println("Session Last Access Time:" + new Date(mySession.getLastAccessedTime()) + "<br>");



out.println("<h3>Request Infomation</h3>");

// Returns the session ID specified by the client.

out.println("Session Id From Request:" + request.getRequestedSessionId() + "<br>");

// Checks whether the requested session ID came in as a cookie.

out.println("Session Id Via Cookie:" + request.isRequestedSessionIdFromCookie() + "<br>");

// Checks whether the requested session ID came in as part of the request URL.

out.println("Session Id Via URL:" + request.isRequestedSessionIdFromURL() + "<br>");

// Checks whether the requested session ID is still valid.

out.println("Valid Session Id:" + request.isRequestedSessionIdValid() + "<br>");



out.println("<a href=" + response.encodeURL("SessionInfoServlet") + ">refresh</a>");

out.println("</body></html>");

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("<html><head><title>Session追踪</title></head>"

+ "<body>" + heading + "<br>"

+ "<h2>Information on Your Session</h2><br>"

+ "/n" + "<table border=1 align=center>/n"

+ "<TH>Info Type<TH>Value" + "<br>"

+ "<tr>/n" + "<td>ID</td>/n"

+ "<td>" + session.getId() +"</td></tr>/n"

+ "<tr>/n" + "<td>CreatTime</td>/n"

+ "<td>" + new Date(session.getCreationTime()) +"</td></tr>/n"

+ "<tr>/n" + "<td>LastAccessTime</td>/n"

+ "<td>" + new Date(session.getLastAccessedTime()) +"</td></tr>/n"

+ "<tr>/n" + "<td>Number of Access</td>/n"

+ "<td>" + accessCount +"</td></tr>/n"

+ "</body></html>");

}

}

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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("<html><head><title>ServletContext测试</title></head><br>"

+ "<body><td>" + accessCount +"</td>/n"

+ "</body></html>");



}

}

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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：<servlet-class>com.bjsxt.servlet.HelloWorldServlet2</servlet-class>

* @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!");



}

}

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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("<table border=1>");

out.println("<tr><td>Content:</td></tr>");

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("<tr>");

out.println("<td>" + rs.getString("cont") + "</td>");

out.println("</tr>");

}

} 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("<table border=1>");

out.println("<tr><td>Content:</td></tr>");



// 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("<tr>");

out.println("<td>" + rs.getString("cont") + "</td>");

out.println("</tr>");

}

} 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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