Question

我无法从eclipse连接到我的数据库。 mysql java连接器＆amp; mysql套接字工厂连接器jar文件包含在构建路径中。我不确定是什么导致NoClassDefFound错误。凭证是正确的，并在代码中省略。

我的代码：

import java.sql.*;

public class TestConnect {

private static String instanceConnectionName = "sampleInstanceName";
private static String databaseName = "sampleDatabaseName";
private static Connection connection = null;
private static String userName="sampleUserName";
private static String password="samplePassword";
private static String dbURL = String.format("jdbc:mysql://google/%s?cloudSqlInstance=%s&"
                                + "socketFactory=com.google.cloud.sql.mysql.SocketFactory",
                                databaseName, instanceConnectionName);

public static void main(String[] args) {
    // TODO Auto-generated method stub
            try {
                Class.forName("com.mysql.jdbc.Driver");
            } catch (Exception e) {
                System.out.println("Where is your MySQL JDBC Driver?");
                e.printStackTrace();
                return;
            }
            System.out.println("MySQL JDBC Driver Registered!");
            CreateConnection();
    }

    public static void CreateConnection() {
            try {
            // connect 
                connection = DriverManager.getConnection(dbURL,userName, password); 
            } catch (SQLException ex) {
                System.out.println("Connection Failed! Check output console");
                ex.printStackTrace();
            }
        }

}

这是pom.xml：

  <dependencies>
<!-- https://mvnrepository.com/artifact/com.google.cloud.sql/mysql-socket-factory -->
<dependency>
    <groupId>com.google.cloud.sql</groupId>
    <artifactId>mysql-socket-factory</artifactId>
    <version>1.0.4</version>
</dependency>
<dependency>                        <!-- http://dev.mysql.com/doc/connector-j/en/ -->
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>5.1.44</version>
</dependency>

  </dependencies>
</project>

以下是错误消息：

java.sql.SQLException: java.lang.NoClassDefFoundError: com/mysql/cj/api/io/SocketFactory
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:964)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:897)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:886)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:860)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:877)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:873)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:443)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:389)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:330)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at TestConnect.CreateConnection(TestConnect.java:32)
    at TestConnect.main(TestConnect.java:26)
Caused by: java.lang.NoClassDefFoundError: com/mysql/cj/api/io/SocketFactory
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$100(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$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 com.mysql.jdbc.MysqlIO.createSocketFactory(MysqlIO.java:3328)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:296)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2189)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2222)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2017)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:779)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
    ... 6 more
Caused by: java.lang.ClassNotFoundException: com.mysql.cj.api.io.SocketFactory
    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)
    ... 32 more

更新

我更新了jar文件并删除了不必要的文件，并相应地更新了pom文件。

这是新的pom文件：

  <dependencies>
<!-- https://mvnrepository.com/artifact/com.google.cloud.sql/mysql-socket-factory-connector-j-6 -->
<dependency>
    <groupId>com.google.cloud.sql</groupId>
    <artifactId>mysql-socket-factory-connector-j-6</artifactId>
    <version>1.0.4</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.google.cloud.sql/jdbc-socket-factory-core -->
<dependency>
    <groupId>com.google.cloud.sql</groupId>
    <artifactId>jdbc-socket-factory-core</artifactId>
    <version>1.0.4</version>
</dependency>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>6.0.6</version>
</dependency>   
  </dependencies>

这是新的错误消息：

Exception in thread "main" java.lang.NoClassDefFoundError: com/google/common/base/Preconditions
    at com.google.cloud.sql.mysql.SocketFactory.connect(SocketFactory.java:41)
    at com.mysql.cj.mysqla.io.MysqlaSocketConnection.connect(MysqlaSocketConnection.java:57)
    at com.mysql.cj.mysqla.MysqlaSession.connect(MysqlaSession.java:122)
    at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:1726)
    at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:1596)
    at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:633)
    at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:347)
    at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:219)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at TestConnect.CreateConnection(TestConnect.java:30)
    at TestConnect.main(TestConnect.java:24)
Caused by: java.lang.ClassNotFoundException: com.google.common.base.Preconditions
    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)
    ... 12 more

Answer 1

com.mysql.cj.api.io.SocketFactory是MySQL Connector / J版本6的一部分。这由mysql-socket-factory-connector-j-6中的SocketFactory使用。但是，您共享的pom.xml使用的是mysql-socket-factory，即版本5数据包，不应使用它。

以前是否有可能使用mysql-socket-factory-connector-j-6并且它在您的库中？这可能允许错误地加载v6 SocketFactory，从而导致此问题。如果是这样，请尝试mvn clean删除旧的jar文件并尝试再次运行。

无法使用eclipse

1 个答案: