遵循的步骤
- MySQL 工作台安装
-
连接器-J下载并解压缩到程序文件中的Mysql文件夹复制
import java.sql.*; public class FirstExample { // JDBC driver name and database URL static final String JDBC_DRIVER = "com.mysql.jdbc.Driver"; static final String DB_URL = "jdbc:mysql://localhost/EMP"; // Database credentials static final String USER = "username"; static final String PASS = "password"; public static void main(String[] args) { Connection conn = null; Statement stmt = null; try{ //STEP 2: Register JDBC driver Class.forName("com.mysql.jdbc.Driver"); //STEP 3: Open a connection System.out.println("Connecting to database..."); conn = DriverManager.getConnection(DB_URL,USER,PASS); //STEP 4: Execute a query System.out.println("Creating statement..."); stmt = conn.createStatement(); String sql; sql = "SELECT id, first, last, age FROM Employees"; ResultSet rs = stmt.executeQuery(sql); //STEP 5: Extract data from result set while(rs.next()){ //Retrieve by column name int id = rs.getInt("id"); int age = rs.getInt("age"); String first = rs.getString("first"); String last = rs.getString("last"); //Display values System.out.print("ID: " + id); System.out.print(", Age: " + age); System.out.print(", First: " + first); System.out.println(", Last: " + last); } //STEP 6: Clean-up environment rs.close(); stmt.close(); conn.close(); }catch(SQLException se){ //Handle errors for JDBC se.printStackTrace(); }catch(Exception e){ //Handle errors for Class.forName e.printStackTrace(); }finally{ //finally block used to close resources try{ if(stmt!=null) stmt.close(); }catch(SQLException se2){ }// nothing we can do try{ if(conn!=null) conn.close(); }catch(SQLException se){ se.printStackTrace(); }//end finally try }//end try System.out.println("Goodbye!"); }//end main }//end FirstExample
此代码用于日食中的新项目。当我运行它时,我发生了此错误
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at FirstExample.main(FirstExample.java:17)
Goodbye!
然后尝试了这个cmd命令
set classpath=C:Program FilesMySQLmysql-connector-java-3.1.14mysql-
connector-java-3.1.14mysql-connector-java-3.1.14-bin.jar;
还是同样的错误该怎么办,请给出一些解释以及您有价值的解决方案谢谢
pom.xml
中添加下面的依赖项
<!-- http://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.6</version>
</dependency>
如果您不使用 Maven,请将此 jar com.mysql.jdbc_5.1.5.jar
添加到您的eclipse build path
rightclick on project--> build path-->configure build path-->libraries-->add external jar
您必须将 JDBC 连接器 jar 文件复制到项目的库文件夹中
或在服务器的库文件夹中
两者都工作正常...
运行时变量无法从这两个位置获取它
您的类路径包含一个空格,因此java.exe
不会正确拾取它。
使用插入符号字符 ^ 转义空格:
set classpath=C:Program^ FilesMySQLmysql-connector-java-3.1.14mysql-connector-java-3.1.14mysql-connector-java-3.1.14-bin.jar;
(并仔细检查路径是否正确!