如何获取 JDBC 连接 ID？

Question

我需要使用 Connection 对象获取 JDBC 连接 id(UUID)。有什么方法可以获取连接ID吗？

Answer 1

好吧，如果您指的是“sql-connection to sql-server”，那么 jdbc 没有这方面的标准工具。这是 jdbc:mysql 的手工示例（注意 - 反射和限制字符）：

    private long getJdbcConnectionId(Connection conn) {
    long cid = 0;
    try {
        Field f_conn__conn = conn.getClass().getSuperclass().getDeclaredField("_conn");
        f_conn__conn.setAccessible(true);
        Object o_conn__conn = f_conn__conn.get(conn);
        Field f_conn__conn__conn = o_conn__conn.getClass().getSuperclass().getDeclaredField("_conn");
        f_conn__conn__conn.setAccessible(true);
        Object o_conn__conn__conn = f_conn__conn__conn.get(o_conn__conn);
        Field f_connectionId = o_conn__conn__conn.getClass().getSuperclass().getDeclaredField("connectionId");
        f_connectionId.setAccessible(true);
        cid = f_connectionId.getLong(o_conn__conn__conn);
        f_connectionId.setAccessible(false);
        f_conn__conn__conn.setAccessible(false);
        f_conn__conn.setAccessible(false);

    } catch (Exception e) {
        e.printStackTrace();
    }
    return cid;
}

Answer 2

编辑：

这样可以避免编译时耦合，使用反射

import java.sql.Connection;
import java.sql.DriverManager;
...
public String getMysqlConnectionId()
{
    try {
        Connection connection = DriverManager.getConnection("jdbc:mysql://host:3306/schema", "myuser", "mypassword");

        Class<?> clazz = Class.forName("com.mysql.jdbc.MySQLConnection");

        Object o = connection.unwrap(clazz);

        return (String) clazz.getMethod("getId").invoke(o).toString();
    } catch ( Exception e ) {
        return e.getMessage();
    }
}

---

通过将

java.sql.Connection

对象投射到

com.mysql.jdbc.MySQLConnection

并使用

getId()

import java.sql.Connection;
import java.sql.DriverManager;
import com.mysql.jdbc.MySQLConnection;
...
public long getMysqlConnectionId()
{
    Connection connection = DriverManager.getConnection("jdbc:mysql://host:3306/schema", "myuser", "mypassword");

    // would throw a ClassCastException in case this is not a mysql one, of course
    return ((MySQLConnection) connection).getId();
}

但这有点可怕的耦合你的项目在编译时与 MySQL

注意：当我对此投反对票时，我不会感到被冒犯，这是应得的;-)

<!-- pom.xml -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>x.y.z</version>
</dependency>

其他一些人显然正在使用

connection.unwrap(com.mysql.jdbc.MySQLConnection)

，这可能感觉更合适一点，但并没有消除与

com.mysql

的编译时耦合 https://github.com/prestodb/presto/issues/9425

Answer 3

这是我如何获取 Oracle SID 的示例：

    public int getConnectionSid() {
    try {
        if (connection == null || connection.isClosed())                
            return -1;            
        if (connectionSid == -1) {                
            try { 
                Method method = connection.getClass().getDeclaredMethod("getSessionId", null);
                method.setAccessible(true);
                connectionSid = (Integer)method.invoke(nativeConnection, null);                    
                method.setAccessible(false);
            } catch (NoSuchMethodException e) {
                return -1;
            } catch (IllegalAccessException e) {
                return -1;
            } catch (InvocationTargetException e) {
                return -1;
            }
        }
        return connectionSid;
    } catch (SQLException e) {            
        return -1;
    }