How do I retrieve available catalogs in database?

By Wayan in JDBC 0 Comment

The examples below show you how to get the available catalog names in MySQL database. The available catalog names can be obtained from the DatabaseMetaData object by calling the getCatalogs() method. This method returns a ResultSet object. We iterate it and get the schema name by calling the getString() method and pass TABLE_CAT as the column name.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;

public class MetadataGetCatalog {
    private static final String URL = "jdbc:mysql://localhost";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            // Gets DatabaseMetaData
            DatabaseMetaData metadata = connection.getMetaData();

            // Retrieves the schema names available in this database
            ResultSet rs = metadata.getCatalogs();

            while (rs.next()) {
                String catalog = rs.getString("TABLE_CAT");
                System.out.println("Catalog: " + catalog);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Here is the list of catalog names available in the MySQL database:

Catalog: kodejava
Catalog: musicdb
Catalog: mysql
Catalog: performance_schema
Catalog: sys

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.1.0</version>
</dependency>

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How do I get the maximum number of concurrent connections?

By Wayan in JDBC 0 Comment

This example shows you how to get the maximum number of concurrent connections to a database that are possible.
To get this information, we use the DatabaseMetaData.getMaxConnections() method call. If the return value is zero, it means that there is no limit or the limit is unknown.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.SQLException;
import java.sql.DriverManager;

public class MaxConnections {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            // Get database meta data.
            DatabaseMetaData metaData = connection.getMetaData();

            // Retrieves the maximum number of concurrent
            // connections to this database that are possible.
            // A result of zero means that there is no limit or
            // the limit is not known.
            int max = metaData.getMaxConnections();
            System.out.println("Max concurrent connections: " + max);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>

Maven Central