JDBC解析3_獲取數據連接信息

 

package book.database;

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * 獲取數據庫和表的元數據
 * 使用DatabaseMetaData獲得數據庫的元數據
 * 使用ResultSetMetaData獲得表的元數據
 */
public class GetMetadata {
    /**
     * 獲得數據庫的元數據
     * @param con   與數據庫的連接
     */
    public static void showDatabaseMetadata(Connection con){
        try {
            // 得到數據庫的元數據
            DatabaseMetaData md = con.getMetaData();
            System.out.println("數據庫" + md.getURL() + "的元數據如下：");

            // 顯示元數據信息
            System.out.println("驅動: " + md.getDriverName());
            System.out.println("驅動版本號: " + md.getDriverVersion());
            System.out.println("登陸用戶名: " + md.getUserName());
            System.out.println("數據庫產品名: " + md.getDatabaseProductName());
            System.out.println("數據庫產品版本號: " + md.getDatabaseProductVersion());
            System.out.println("支持的SQL關鍵字: ");
            System.out.println(md.getSQLKeywords());
            System.out.println("操作數字的函數: ");
            System.out.println(md.getNumericFunctions());
            System.out.println("操作字符串的函數: ");
            System.out.println(md.getStringFunctions());
            System.out.println("系統函數: ");
            System.out.println(md.getSystemFunctions());
            System.out.println("時間和日期函數: ");
            System.out.println(md.getTimeDateFunctions());

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    /**
     * 顯示數據表的元數據，主要是列的信息
     * @param con   與數據庫的連接
     * @param tableName  數據表名
     */
    public static void showTableMetadata(Connection con, String tableName){
        String sql = "SELECT * FROM " + tableName;
        Statement sm = null;
        try {
            // 首先獲得表的所有數據
            sm = con.createStatement();
            ResultSet rs = sm.executeQuery(sql);

            // 得到結果集的元數據
            ResultSetMetaData md = rs.getMetaData();

            System.out.println("數據表" + tableName + "的元數據如下：");
            // 表的列數
            int columnCount = md.getColumnCount();
            System.out.println("column count: " + columnCount);
            System.out.println();
            StringBuffer sb = new StringBuffer("");
            sb.append("sn\tname\t\t").append("type\t\t");
            sb.append("scale\t").append("isNullable");
            System.out.println(sb);
            sb.delete(0, sb.length());
            // 輸出列的屬性信息
            for (int i=1; i<=columnCount; i++){
                sb.append(i).append("\t");
                sb.append(md.getColumnName(i)).append("\t\t");
                sb.append(md.getColumnTypeName(i)).append("\t\t");
                sb.append(md.getScale(i)).append("\t");
                sb.append(md.isNullable(i));
                System.out.println(sb);
                sb.delete(0, sb.length());
            }
            rs.close();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 關閉Statement
            if (sm != null){
                try {
                    sm.close();
                } catch (SQLException e1) {
                    e1.printStackTrace();
                }
            }
        }
    }

    public static void main(String[] args) throws ClassNotFoundException,
            SQLException {
        String dbName = "studentdb";
        String tableName = "student_basic";
        String userName = "test";
        String password = "test";

        Connection con = null;
        try {
            // 獲得數據庫連接
            con = DBConnector.getMySQLConnection(null, null, null, dbName,
                    userName, password);
            // 顯示數據庫的元信息
            GetMetadata.showDatabaseMetadata(con);
            System.out.println();
            // 顯示數據表的元信息
            GetMetadata.showTableMetadata(con, tableName);
        } catch (ClassNotFoundException e1) {
            throw e1;
        } catch (SQLException e2) {
            throw e2;
        } finally {
            // 關閉數據庫連接
            if (con != null) {
                try {
                    con.close();
                } catch (SQLException e1) {
                    e1.printStackTrace();
                }
            }
        }
    }
}