[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>
<!--单选框示例-->
<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>
<!--密码输入框-->
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();
}
}
}
