eclipse 编译错误 - com.mysql.jdbc.Driver 无法解析为变量
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Compilation error - com.mysql.jdbc.Driver cannot be resolved to a variable
提问by rpat
I am barely familiar with pre-bundled STS. I am trying out JDBC for MySQL in Eclipse/Spring on Fedora 17
我对预捆绑的 STS 几乎不熟悉。我正在 Fedora 17 上的 Eclipse/Spring 中试用 MySQL 的 JDBC
Downloaded the mysql JDBC drivers (mysql-connector-java-5.1.22-bin.jar). Then in the IDE
下载了 mysql JDBC 驱动程序 (mysql-connector-java-5.1.22-bin.jar)。然后在IDE中
- Created a project and named it JDBC
- Created a folder called 'lib' under the project
- Went to Project > Properties . Selected the Java Build Path, then selected the 'Libraries' tab. clicked on 'Add Jars' Selected JDBC > lib > mysql---.jar and clicked OK. This added under the Project Explorer pane a 'Referenced Libraries', under which I see the mysql jar file.
- Wrote the following code under the project
- 创建了一个项目并将其命名为JDBC
- 在项目下创建了一个名为“lib”的文件夹
- 转到 Project > Properties 。选择 Java 构建路径，然后选择“库”选项卡。单击“添加罐子”选定的 JDBC > lib > mysql---.jar 并单击确定。这在项目资源管理器窗格下添加了一个“参考库”，我在其中看到了 mysql jar 文件。
- 在项目下写了如下代码
I kind of thought I had done what was needed to compile. However, I am seeing
我有点以为我已经完成了编译所需的工作。然而，我看到
Class.forName(com.mysql.jdbc.Driver);
Class.forName(com.mysql.jdbc.Driver);
com.mysql.jdbc.Driver cannot be resolved to a variable
com.mysql.jdbc.Driver 无法解析为变量
Can you tell me what's wrong here.
你能告诉我这里有什么问题吗？
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class TestJDBC {
/**
* @param args
*/
public static void main(String[] args) throws Exception{
// TODO Auto-generated method stub
Connection connection = null;
Statement statement = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
Class.forName(com.mysql.jdbc.Driver);
connection = DriverManager.getConnection("jdbc:mysql://localhost/testdb?" +
"user=myuser&password=mypwd");
if (connection != null) {
System.out.println ("Connected may be?");
connection.close();
}
else {
System.out.println ("Not connected?");
}
}
catch (Exception e) {
connection.close();
}
}
}
采纳答案by mazaneicha
Class.forName("com.mysql.jdbc.Driver");
or
或者
Class.forName(com.mysql.jdbc.Driver.class.getName());
will work better. (The 2nd one compiles but doesn't really make sense cause it assumes that class is already loaded :)
会工作得更好。（第二个编译但实际上没有意义，因为它假设类已经加载:)
回答by Chris Gerken
You want to use:
你想使用：
Class.forName("com.mysql.jdbc.Driver");
In the future, note that the compiler was telling you what it was expecting: a variable. You just have to figure out how to modify or convert what you have into what it wants. In this case, anything that converts to a value (a constant, a variable or a method returning a value) can be used.
将来，请注意编译器会告诉您它期望的是什么：一个变量。你只需要弄清楚如何修改或转换你拥有的东西。在这种情况下，可以使用任何转换为值的东西（常量、变量或返回值的方法）。
