Using metadata to analyze databases in Java Foundation Series 15:JDBC
（1）DatabaseMetaData：
package javase.jdbc;import java.sql.Connection;import java.sql.DatabaseMetaData;import java.sql.ResultSet;import java.sql.SQLException;public class DatabaseMetaDataDemo { public static void main(String[] args) { Connection connection = JDBCConnection.getConnection(); try { DatabaseMetaData dMetaData = connection.getMetaData(); //instantiate metadata System.out.println("database name: " + dMetaData.getDatabaseProductName()); System.out.println("Database version: " + dMetaData.getDatabaseProductVersion()); ResultSet resultSet = dMetaData.getPrimaryKeys(null, null, "users"); while (resultSet.next()) { System.out.println("Table Category: " + resultSet.getString(1)); System.out.println("table schema: " + resultSet.getString(2)); System.out.println("table name: " + resultSet.getString(3)); System.out.println("Column Name: " + resultSet.getString(4)); System.out.println("PK: " + resultSet.getString(5)); System.out.println("Primary key name: " + resultSet.getString(6)); } } catch (SQLException e) { e.printStackTrace(); } }}
Output:
Database Name: MySQL Database Version: 5.5.19 Table Category: jdbcdemo Table Mode: null Table Name: users Column Name: id Primary Key: 1 Primary Key Name: PRIMARY
（2）ResultSetMetaData：
package javase.jdbc;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSetMetaData;import java.sql.SQLException;public class ResultSetMetaDataDemo { public static void main(String[] args) { String sql = "SELECT id,username,password,classId FROM users"; Connection connection = JDBCConnection.getConnection(); try { PreparedStatement pStatement = connection.prepareStatement(sql); ResultSetMetaData rSetMetaData = pStatement.getMetaData(); System.out.println("Return data has" + rSetMetaData.getColumnCount() + "fields"); if (rSetMetaData.isAutoIncrement(1)) System.out.println(rSetMetaData.getColumnName(1) + "field is self-increasing"); } catch (SQLException e) { e.printStackTrace(); } }}
Output:
The returned data has 4 fields. The id field is self-increasing.
