Mysql数据库exception

线程“main”中的exceptionjava.lang.Error：未解决的编译问题：类型不匹配：无法从java.sql.Statement转换为com.mysql.jdbc.Statement

我是java的初学者我正在尝试使用mysql数据库我已经从mysql.com下载了mysql-connector-java-5.1.23-bin.jar文件，我已将此jar文件添加到我的项目的构建路径中但是以下代码中存在错误线程“main”中的exceptionjava.lang.Error：未解决的编译问题：类型不匹配：无法从java.sql.Statement转换为com.mysql.jdbc.Statement

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package com.example.demo; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import com.mysql.jdbc.Connection; import com.mysql.jdbc.Statement; public class DBConnect { private static final String userName = "root"; private static final String userpwd = "sverma"; private static final String CONN_STR = "jdbc:mysql://localhost:3306/phpweb_db"; public static void main(String[] args) throws SQLException { Connection conn = null; Statement st = null; ResultSet rs = null; try { DriverManager.getConnection(CONN_STR, userName, userpwd); st=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY); rs = st.executeQuery("select * from user"); rs.last(); System.out.println("No of rows: " + rs.getRow()); // System.out.println("Connected Successfully..."); } catch (SQLException e) { System.err.println(e); } finally { if (rs != null) { rs.close(); } if (st != null) { st.close(); } if (conn != null) { conn.close(); } } } 

}

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Answer 1

错误的课程

 import com.mysql.jdbc.Connection; import com.mysql.jdbc.Statement; 

应该

 import java.sql.Connection; import java.sql.Statement; 

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事实上，java将特定数据库引擎的所有内容分离。 永远不需要导入MySQL（或ProgressSQL或…）类。

要在运行时使这些类可用， try之后的第一件事是在获得连接之前：

 Class.forName("com.mysql.jdbc.Driver"); 

此技术允许从配置文件中读取所有字符串，并编写与数据库无关的代码。

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缺少：conn = …

 conn = DriverManager.getConnection(CONN_STR, userName, userpwd); 

Answer 2

 package com.example.demo; import java.sql.*; public class DBConnect { private static final String userName = "root"; private static final String userpwd = "sverma"; private static final String CONN_STR = "jdbc:mysql://localhost:3306/phpweb_db"; public static void main(String[] args) throws SQLException { Connection conn; Statement st; ResultSet rs; try { Class.forName("com.mysql.jdbc.Driver"); DriverManager.getConnection(CONN_STR, userName, userpwd); st=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY); rs = st.executeQuery("select * from user"); rs.last(); System.out.println("No of rows: " + rs.getRow()); // System.out.println("Connected Successfully..."); } catch (SQLException e) { System.err.println(e); } finally { if (rs != null) { rs.close(); } if (st != null) { st.close(); } if (conn != null) { conn.close(); } } }