最近想要寫一個根據數據庫表結構生成實體、mapper接口、mapping映射文件、service類的簡單代碼生成工具,所以查閱了一些資料,怎樣獲取數據庫的表、表中字段、字段類型、字段注釋等信息。
最后寫了一個簡單的工具類,代碼如下:
package com.lnjecit.generator.util; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.sql.*; import java.util.ArrayList; import java.util.List; public class DatabaseUtil { private final static Logger LOGGER = LoggerFactory.getLogger(DatabaseUtil.class); private static final String DRIVER = "com.mysql.jdbc.Driver"; private static final String URL = "jdbc:mysql://localhost:3306/javaweb?useUnicode=true&characterEncoding=utf8"; private static final String USERNAME = "root"; private static final String PASSWORD = "mysql"; private static final String SQL = "SELECT * FROM ";// 數據庫操作 static { try { Class.forName(DRIVER); } catch (ClassNotFoundException e) { LOGGER.error("can not load jdbc driver", e); } } /** * 獲取數據庫連接 * * @return */ public static Connection getConnection() { Connection conn = null; try { conn = DriverManager.getConnection(URL, USERNAME, PASSWORD); } catch (SQLException e) { LOGGER.error("get connection failure", e); } return conn; } /** * 關閉數據庫連接 * @param conn */ public static void closeConnection(Connection conn) { if(conn != null) { try { conn.close(); } catch (SQLException e) { LOGGER.error("close connection failure", e); } } } /** * 獲取數據庫下的所有表名 */ public static List<String> getTableNames() { List<String> tableNames = new ArrayList<>(); Connection conn = getConnection(); ResultSet rs = null; try { //獲取數據庫的元數據 DatabaseMetaData db = conn.getMetaData(); //從元數據中獲取到所有的表名 rs = db.getTables(null, null, null, new String[] { "TABLE" }); while(rs.next()) { tableNames.add(rs.getString(3)); } } catch (SQLException e) { LOGGER.error("getTableNames failure", e); } finally { try { rs.close(); closeConnection(conn); } catch (SQLException e) { LOGGER.error("close ResultSet failure", e); } } return tableNames; } /** * 獲取表中所有字段名稱 * @param tableName 表名 * @return */ public static List<String> getColumnNames(String tableName) { List<String> columnNames = new ArrayList<>(); //與數據庫的連接 Connection conn = getConnection(); PreparedStatement pStemt = null; String tableSql = SQL + tableName; try { pStemt = conn.prepareStatement(tableSql); //結果集元數據 ResultSetMetaData rsmd = pStemt.getMetaData(); //表列數 int size = rsmd.getColumnCount(); for (int i = 0; i < size; i++) { columnNames.add(rsmd.getColumnName(i + 1)); } } catch (SQLException e) { LOGGER.error("getColumnNames failure", e); } finally { if (pStemt != null) { try { pStemt.close(); closeConnection(conn); } catch (SQLException e) { LOGGER.error("getColumnNames close pstem and connection failure", e); } } } return columnNames; } /** * 獲取表中所有字段類型 * @param tableName * @return */ public static List<String> getColumnTypes(String tableName) { List<String> columnTypes = new ArrayList<>(); //與數據庫的連接 Connection conn = getConnection(); PreparedStatement pStemt = null; String tableSql = SQL + tableName; try { pStemt = conn.prepareStatement(tableSql); //結果集元數據 ResultSetMetaData rsmd = pStemt.getMetaData(); //表列數 int size = rsmd.getColumnCount(); for (int i = 0; i < size; i++) { columnTypes.add(rsmd.getColumnTypeName(i + 1)); } } catch (SQLException e) { LOGGER.error("getColumnTypes failure", e); } finally { if (pStemt != null) { try { pStemt.close(); closeConnection(conn); } catch (SQLException e) { LOGGER.error("getColumnTypes close pstem and connection failure", e); } } } return columnTypes; } /** * 獲取表中字段的所有注釋 * @param tableName * @return */ public static List<String> getColumnComments(String tableName) { List<String> columnTypes = new ArrayList<>(); //與數據庫的連接 Connection conn = getConnection(); PreparedStatement pStemt = null; String tableSql = SQL + tableName; List<String> columnComments = new ArrayList<>();//列名注釋集合 ResultSet rs = null; try { pStemt = conn.prepareStatement(tableSql); rs = pStemt.executeQuery("show full columns from " + tableName); while (rs.next()) { columnComments.add(rs.getString("Comment")); } } catch (SQLException e) { e.printStackTrace(); } finally { if (rs != null) { try { rs.close(); closeConnection(conn); } catch (SQLException e) { LOGGER.error("getColumnComments close ResultSet and connection failure", e); } } } return columnComments; } public static void main(String[] args) { List<String> tableNames = getTableNames(); System.out.println("tableNames:" + tableNames); for (String tableName : tableNames) { System.out.println("ColumnNames:" + getColumnNames(tableName)); System.out.println("ColumnTypes:" + getColumnTypes(tableName)); System.out.println("ColumnComments:" + getColumnComments(tableName)); } } }
在運行代碼之前,先將數據庫配置進行修改,再運行代碼就可以獲取數據庫表的詳細結構了。
后續可以以此為基礎寫一個通過表結構生成實體、接口、映射文件的簡單代碼生成器。減少ssm項目開發中編碼工作。
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