获取连接的mysql数据库名称(JDBC) [英] Get the connected mysql database name (JDBC)

问题描述

如何从连接对象获取数据库名称的名称

try {
    this.ds = (DataSource) new InitialContext().lookup("java:comp/env/jdbc/amger");
} catch (NamingException ne) {
}
Connection conObj = ds.getConnection();

如何从con中获取该数据库名称

解决方案

从JDBC Connection对象本身获取数据库名称的最直接方法可能是通过getCatalog()方法:

Connection#getCatalog()

但是，正如Konstantin在下面的评论中指出的那样，如果通过发出USE dbname语句更改当前的MySQL数据库，则该值不会更改.

getCatalog()在

的应用程序中可能仍然有用

• 不更改数据库，或者
• 通过使用setCatalog()更改当前数据库来执行"JDBC方式"

但是对于MySQL而言，使用SELECT DATABASE()似乎总体上更安全.

还请注意，getCatalog()与实际当前数据库之间的这种潜在差异取决于特定JDBC驱动程序的行为.出于好奇，我尝试使用适用于SQL Server的Microsoft JDBC驱动程序4.0进行类似操作，并且.getCatalog()实际上确实在运行USE dbname语句后立即意识到对当前数据库的更改.即是代码

 String connectionUrl = "jdbc:sqlserver://localhost:52865;"
        + "databaseName=myDb;" + "integratedSecurity=true";
try (Connection con = DriverManager.getConnection(connectionUrl)) {
    System.out.println(String.format(
            "getCatalog() returns: %s", 
            con.getCatalog()));
    try (Statement s = con.createStatement()) {
        System.out.println("           Executing: USE master");
        s.execute("USE master");
    }
    System.out.println(String.format(
            "getCatalog() returns: %s", 
            con.getCatalog()));
} catch (Exception e) {
    e.printStackTrace(System.out);
}
 

产生了以下结果:

 getCatalog() returns: myDb
           Executing: USE master
getCatalog() returns: master
 

How can get the name of the database name from connection object

try {
    this.ds = (DataSource) new InitialContext().lookup("java:comp/env/jdbc/amger");
} catch (NamingException ne) {
}
Connection conObj = ds.getConnection();

How do I get that Database name from con

解决方案

Probably the most straightforward way to get the database name from the JDBC Connection object itself is via the getCatalog() method:

Connection#getCatalog()

However, as Konstantin pointed out in his comment below, that value will not change if the current MySQL database is changed by issuing a USE dbname statement.

getCatalog() might still be useful in an application that

• does not change databases, or
• does things "The JDBC Way" by using setCatalog() to change the current database,

but for MySQL, using SELECT DATABASE() appears to be safer overall.

Note also that this potential discrepancy between getCatalog() and the actual current database depends on the behaviour of the particular JDBC driver. Out of curiosity I tried something similar with the Microsoft JDBC Driver 4.0 for SQL Server and .getCatalog() was indeed aware of the change to the current database immediately after running a USE dbname statement. That is, the code

String connectionUrl = "jdbc:sqlserver://localhost:52865;"
        + "databaseName=myDb;" + "integratedSecurity=true";
try (Connection con = DriverManager.getConnection(connectionUrl)) {
    System.out.println(String.format(
            "getCatalog() returns: %s", 
            con.getCatalog()));
    try (Statement s = con.createStatement()) {
        System.out.println("           Executing: USE master");
        s.execute("USE master");
    }
    System.out.println(String.format(
            "getCatalog() returns: %s", 
            con.getCatalog()));
} catch (Exception e) {
    e.printStackTrace(System.out);
}

produced the following results:

getCatalog() returns: myDb
           Executing: USE master
getCatalog() returns: master

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