• maven的一个应用

    使用maven给WEB项目添加，完成 用户登陆+mysql数据库

     1.com.cdl.entity包

    1. package com.cdl.entity;
    2.  
    3. public class User {
    4.  
    5. 	    private Long id;
    6.  
    7. 	    private String name;
    8.  
    9. 	    private String loginName;
    10.  
    11. 	    private String pwd;
    12.  
    13. 	    private Long rid;
    14.  
    15. 		public Long getId() {
    16. 			return id;
    17. 		}
    18.  
    19. 		public void setId(Long id) {
    20. 			this.id = id;
    21. 		}
    22.  
    23. 		public String getName() {
    24. 			return name;
    25. 		}
    26.  
    27. 		public void setName(String name) {
    28. 			this.name = name;
    29. 		}
    30.  
    31. 		public String getLoginName() {
    32. 			return loginName;
    33. 		}
    34.  
    35. 		public void setLoginName(String loginName) {
    36. 			this.loginName = loginName;
    37. 		}
    38.  
    39. 		public String getPwd() {
    40. 			return pwd;
    41. 		}
    42.  
    43. 		public void setPwd(String pwd) {
    44. 			this.pwd = pwd;
    45. 		}
    46.  
    47. 		public Long getRid() {
    48. 			return rid;
    49. 		}
    50.  
    51. 		public void setRid(Long rid) {
    52. 			this.rid = rid;
    53. 		}
    54.  
    55. 		public User() {
    56. 			super();
    57. 			// TODO Auto-generated constructor stub
    58. 		}
    59.  
    60. 		@Override
    61. 		public String toString() {
    62. 			return "User [id=" + id + ", name=" + name + ", loginName=" + loginName + ", pwd=" + pwd + ", rid=" + rid + "]";
    63. 		}
    64. 	    
    65. 	    
    66.  
    67.  
    68. }

    2.com.cdl.util包

    DBAccess

    1. package com.cdl.util;
    2.  
    3. import java.io.InputStream;
    4. import java.sql.Connection;
    5. import java.sql.DriverManager;
    6. import java.sql.ResultSet;
    7. import java.sql.SQLException;
    8. import java.sql.Statement;
    9. import java.util.Properties;
    10.  
    11. /**
    12.  * 提供了一组获得或关闭数据库对象的方法
    13.  * 
    14.  */
    15. public class DBAccess {
    16. 	private static String driver;
    17. 	private static String url;
    18. 	private static String user;
    19. 	private static String password;
    20.  
    21. 	static {// 静�?�块执行�?次，加载 驱动�?�?
    22. 		try {
    23. 			InputStream is = DBAccess.class
    24. 					.getResourceAsStream("config.properties");
    25.  
    26. 			Properties properties = new Properties();
    27. 			properties.load(is);
    28.  
    29. 			driver = properties.getProperty("driver");
    30. 			url = properties.getProperty("url");
    31. 			user = properties.getProperty("user");
    32. 			password = properties.getProperty("pwd");
    33.  
    34. 			Class.forName(driver);
    35. 		} catch (Exception e) {
    36. 			e.printStackTrace();
    37. 			throw new RuntimeException(e);
    38. 		}
    39. 	}
    40.  
    41. 	/**
    42. 	 * 获得数据连接对象
    43. 	 * 
    44. 	 * @return
    45. 	 */
    46. 	public static Connection getConnection() {
    47. 		try {
    48. 			Connection conn = DriverManager.getConnection(url, user, password);
    49. 			return conn;
    50. 		} catch (SQLException e) {
    51. 			e.printStackTrace();
    52. 			throw new RuntimeException(e);
    53. 		}
    54. 	}
    55.  
    56. 	public static void close(ResultSet rs) {
    57. 		if (null != rs) {
    58. 			try {
    59. 				rs.close();
    60. 			} catch (SQLException e) {
    61. 				e.printStackTrace();
    62. 				throw new RuntimeException(e);
    63. 			}
    64. 		}
    65. 	}
    66.  
    67. 	public static void close(Statement stmt) {
    68. 		if (null != stmt) {
    69. 			try {
    70. 				stmt.close();
    71. 			} catch (SQLException e) {
    72. 				e.printStackTrace();
    73. 				throw new RuntimeException(e);
    74. 			}
    75. 		}
    76. 	}
    77.  
    78. 	public static void close(Connection conn) {
    79. 		if (null != conn) {
    80. 			try {
    81. 				conn.close();
    82. 			} catch (SQLException e) {
    83. 				e.printStackTrace();
    84. 				throw new RuntimeException(e);
    85. 			}
    86. 		}
    87. 	}
    88.  
    89. 	public static void close(Connection conn, Statement stmt, ResultSet rs) {
    90. 		close(rs);
    91. 		close(stmt);
    92. 		close(conn);
    93. 	}
    94.  
    95. 	public static boolean isOracle() {
    96. 		return "oracle.jdbc.driver.OracleDriver".equals(driver);
    97. 	}
    98.  
    99. 	public static boolean isSQLServer() {
    100. 		return "com.microsoft.sqlserver.jdbc.SQLServerDriver".equals(driver);
    101. 	}
    102. 	
    103. 	public static boolean isMysql() {
    104. 		return "com.mysql.cj.jdbc.Driver".equals(driver);
    105. 	}
    106.  
    107. 	public static void main(String[] args) {
    108. 		Connection conn = DBAccess.getConnection();
    109. 		System.out.println(conn);
    110. 		DBAccess.close(conn);
    111. 		System.out.println("isOracle�?" + isOracle());
    112. 		System.out.println("isSQLServer�?" + isSQLServer());
    113. 		System.out.println("isMysql�?" + isMysql());
    114. 		System.out.println("数据库连�?(关闭)成功");
    115. 	}
    116. }

     DBHelper 

    1. package com.cdl.util;
    2.  
    3. 	import java.io.InputStream;
    4. 	import java.sql.Connection;
    5. 	import java.sql.DriverManager;
    6. 	import java.sql.PreparedStatement;
    7. 	import java.sql.ResultSet;
    8. 	import java.sql.SQLException;
    9. 	import java.sql.Statement;
    10. 	import java.util.Properties;
    11.  
    12. 	/**
    13. 	 * 提供了一组获得或关闭数据库对象的方法
    14. 	 * 
    15. 	 */
    16. 	public class DBHelper {
    17. 		private static String driver;
    18. 		private static String url;
    19. 		private static String user;
    20. 		private static String password;
    21.  
    22. 		static {// 静态块执行一次，加载 驱动一次
    23. 			try {
    24. 				InputStream is = DBHelper.class
    25. 						.getResourceAsStream("config.properties");
    26.  
    27. 				Properties properties = new Properties();
    28. 				properties.load(is);
    29.  
    30. 				driver = properties.getProperty("driver");
    31. 				url = properties.getProperty("url");
    32. 				user = properties.getProperty("user");
    33. 				password = properties.getProperty("pwd");
    34.  
    35. 				Class.forName(driver);
    36. 			} catch (Exception e) {
    37. 				e.printStackTrace();
    38. 				throw new RuntimeException(e);
    39. 			}
    40. 		}
    41.  
    42. 		/**
    43. 		 * 获得数据连接对象
    44. 		 * 
    45. 		 * @return
    46. 		 */
    47. 		public static Connection getConnection() {
    48. 			try {
    49. 				Connection conn = DriverManager.getConnection(url, user, password);
    50. 				return conn;
    51. 			} catch (SQLException e) {
    52. 				e.printStackTrace();
    53. 				throw new RuntimeException(e);
    54. 			}
    55. 		}
    56.  
    57. 		public static void close(ResultSet rs) {
    58. 			if (null != rs) {
    59. 				try {
    60. 					rs.close();
    61. 				} catch (SQLException e) {
    62. 					e.printStackTrace();
    63. 					throw new RuntimeException(e);
    64. 				}
    65. 			}
    66. 		}
    67.  
    68. 		public static void close(Statement stmt) {
    69. 			if (null != stmt) {
    70. 				try {
    71. 					stmt.close();
    72. 				} catch (SQLException e) {
    73. 					e.printStackTrace();
    74. 					throw new RuntimeException(e);
    75. 				}
    76. 			}
    77. 		}
    78.  
    79. 		public static void close(Connection conn) {
    80. 			if (null != conn) {
    81. 				try {
    82. 					conn.close();
    83. 				} catch (SQLException e) {
    84. 					e.printStackTrace();
    85. 					throw new RuntimeException(e);
    86. 				}
    87. 			}
    88. 		}
    89. 		
    90. 		public static void myClose(Connection con,PreparedStatement ps,ResultSet rs) {
    91. 			try {
    92. 				if(rs!=null) {
    93. 					rs.close();
    94. 				}
    95. 				if(ps!=null) {
    96. 					ps.close();
    97. 				}
    98. 				if(con!=null&&!con.isClosed()) {
    99. 					con.close();
    100. 				}
    101. 			} catch (Exception e) {
    102. 				e.printStackTrace();
    103. 			}
    104. 		}
    105.  
    106. 		public static void close(Connection conn, Statement stmt, ResultSet rs) {
    107. 			close(rs);
    108. 			close(stmt);
    109. 			close(conn);
    110. 		}
    111.  
    112. 		public static boolean isOracle() {
    113. 			return "oracle.jdbc.driver.OracleDriver".equals(driver);
    114. 		}
    115.  
    116. 		public static boolean isSQLServer() {
    117. 			return "com.microsoft.sqlserver.jdbc.SQLServerDriver".equals(driver);
    118. 		}
    119. 		
    120. 		public static boolean isMysql() {
    121. 			return "com.mysql.jdbc.Driver".equals(driver);
    122. 		}
    123.  
    124. 		public static void main(String[] args) {
    125. 			Connection conn = DBHelper.getConnection();
    126. 			DBHelper.close(conn);
    127. 			System.out.println("isOracle：" + isOracle());
    128. 			System.out.println("isSQLServer：" + isSQLServer());
    129. 			System.out.println("isMysql：" + isMysql());
    130. 			System.out.println("数据库连接(关闭)成功");
    131. 		}
    132. 	}
    133.  
    134.  
    135.

     config.properties

    1. #oracle9i
    2. #driver=oracle.jdbc.driver.OracleDriver
    3. #url=jdbc:oracle:thin:@localhost:1521:ora9
    4. #user=test
    5. #pwd=test
    6.  
    7.  
    8. #sql2005
    9. #driver=com.microsoft.sqlserver.jdbc.SQLServerDriver
    10. #url=jdbc:sqlserver://localhost:1423;DatabaseName=test
    11. #user=sa
    12. #pwd=sa
    13.  
    14.  
    15. #sql2000
    16. #driver=com.microsoft.jdbc.sqlserver.SQLServerDriver
    17. #url=jdbc:microsoft:sqlserver://localhost:1433;databaseName=unit6DB
    18. #user=sa
    19. #pwd=888888
    20.  
    21. #mysql5
    22. #driver=com.mysql.jdbc.Driver
    23. #url=jdbc:mysql://127.0.0.1:3306/mybatis_ssm?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT
    24. #user=mybatis_ssm
    25. #pwd=xiaoli
    26.  
    27. #mysql8
    28. driver=com.mysql.cj.jdbc.Driver
    29. url=jdbc:mysql://127.0.0.1:3306/mysql?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT&useSSL=true
    30. user=root
    31. pwd=123456
    32.  
    33.  
    34.

    3.com.cdl.dao

    1. package com.cdl.dao;
    2.  
    3. import java.sql.Connection;
    4. import java.sql.PreparedStatement;
    5. import java.sql.ResultSet;
    6.  
    7. import com.cdl.entity.User;
    8. import com.cdl.util.DBAccess;
    9. import com.cdl.util.DBHelper;
    10.  
    11. public class UserDao {
    12. //	登录
    13. 	public User login(User u){
    14. 		Connection con=null;
    15. 		PreparedStatement ps=null;
    16. 		ResultSet rs=null;
    17. 		try {
    18. 			con=DBAccess.getConnection();
    19. 			String sql="select * from t_oa_user where loginName=? and pwd=?";
    20. 			ps = con.prepareStatement(sql);
    21. 			ps.setString(1, u.getLoginName());
    22. 			ps.setString(2, u.getPwd());
    23. 			rs=ps.executeQuery();
    24. 			if(rs.next()) {
    25. 				u.setId(rs.getLong(1));
    26. 				u.setName(rs.getString(2));
    27. 				u.setLoginName(rs.getString(3));
    28. 				u.setPwd(rs.getString(4));
    29. 				u.setRid(rs.getLong(5));
    30. 			}
    31. 		} catch (Exception e) {
    32. 			e.printStackTrace();
    33. 		}finally {
    34. 			DBHelper.close(con, ps, rs);
    35. 		}
    36. 		return u;
    37. 	}
    38. }
    39.

    4.com.cdl.web

    1. package com.cdl.web;
    2.  
    3. import java.io.IOException;
    4. import java.io.PrintWriter;
    5.  
    6. import javax.servlet.ServletException;
    7. import javax.servlet.annotation.WebServlet;
    8. import javax.servlet.http.HttpServlet;
    9. import javax.servlet.http.HttpServletRequest;
    10. import javax.servlet.http.HttpServletResponse;
    11.  
    12. import com.cdl.dao.UserDao;
    13. import com.cdl.entity.User;
    14.  
    15. @WebServlet("/login.do")
    16. public class UserAction extends HttpServlet{
    17. 	@Override
    18. 	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    19. 		doPost(req, resp);
    20. 	}
    21. 	
    22. 	@Override
    23. 	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    24. 		//设置编码方式
    25. 		req.setCharacterEncoding("utf-8");
    26. 		resp.setCharacterEncoding("utf-8");
    27. 		resp.setContentType("text/html; charset=UTF-8");
    28. 				
    29. 		//拿out
    30. 		PrintWriter out = resp.getWriter();
    31. 				
    32. 		UserDao ud=new UserDao();
    33. 		//接收表单传值
    34. 		String sname = req.getParameter("name");
    35. 		String pwd = req.getParameter("pwd");
    36. 		User u=new User();
    37. 		u.setLoginName(sname);
    38. 		u.setPwd(pwd);
    39. 		User u1 = ud.login(u);
    40. 		if(u1!=null) {
    41. 			out.print("");
    42. 		}else{
    43. 			out.print("");
    44. 		}
    45. 	}
    46. }
    47.

    页面login.jsp

    1. <%@ page language="java" contentType="text/html; charset=UTF-8"
    2.     pageEncoding="UTF-8"%>
    3. html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    4. <html>
    5. <head>
    6. <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    7. <title>登陆title>
    8. head>
    9. <body>
    10. 	<h2>登陆 界面h2>
    11. 	<form action="login.do">
    12. 		用户名：<input type="text" name="name"/>
    13. 		密码：<input type="text" name="pwd"/>
    14. 		<input type="submit" />
    15. 		<input type="reset" />
    16. 	form>
    17. body>
    18. html>

    效果：

     输入正确用户名和密码

     

    原因：版本不同

    检查步骤

    第一步：检查项目中是否引入mysql-connector-java驱动包，如果没引入，请先引入对应版本的该包。

    第二步：检查mysql-connector-java驱动包的版本和配置的driver-class-name（驱动类名）是否一致。如果不一致会导致找不到Driver类，必须将版本和配置的驱动类名对应一致。

     结论：不同版本的mysql-connector-java驱动包的Driver类所在的位置不同，在5.x版本中Driver类在com.mysql.jdbc包路径下，到了6.x版中Driver类在com.mysql.cj.jdbc包路径下。

    如果我们在项目中配置的driver-class-name为com.mysql.jdbc.Driver，则对应的mysql-connector-java版本应该是5.x。

    如果我们在项目中配置的driver-class-name为com.mysql.cj.jdbc.Driver，则对应的mysql-connector-java版本应该是6.x。

     将driver-class-name更换

    1. #oracle9i
    2. #driver=oracle.jdbc.driver.OracleDriver
    3. #url=jdbc:oracle:thin:@localhost:1521:ora9
    4. #user=test
    5. #pwd=test
    6.  
    7.  
    8. #sql2005
    9. #driver=com.microsoft.sqlserver.jdbc.SQLServerDriver
    10. #url=jdbc:sqlserver://localhost:1423;DatabaseName=test
    11. #user=sa
    12. #pwd=sa
    13.  
    14.  
    15. #sql2000
    16. #driver=com.microsoft.jdbc.sqlserver.SQLServerDriver
    17. #url=jdbc:microsoft:sqlserver://localhost:1433;databaseName=unit6DB
    18. #user=sa
    19. #pwd=888888
    20.  
    21. #mysql5
    22. #driver=com.mysql.jdbc.Driver
    23. #url=jdbc:mysql://127.0.0.1:3306/mybatis_ssm?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT
    24. #user=mybatis_ssm
    25. #pwd=xiaoli
    26.  
    27. #mysql8
    28. driver=com.mysql.jdbc.Driver
    29. url=jdbc:mysql://127.0.0.1:3306/mysql?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT&useSSL=true
    30. user=root
    31. pwd=123456
    32.  
    33.  
    34.

     注意：我的依赖是5.x的 我就没更换依赖了

    再运行

     

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  • 原文地址：https://blog.csdn.net/weixin_62735525/article/details/126155066