java获取mysql数据库表字段字段类型字段注释

Posted 2021-04-29 搬砖有道

最近想要写一个根据数据库表结构生成实体、mapper接口、mapping映射文件、service类的简单代码生成工具，所以查阅了一些资料，怎样获取数据库的表、表中字段、字段类型、字段注释等信息。最后写了一个简单的工具类，代码如下：

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 ";// 数据库操作
 static { try { Class.forName(DRIVER); } catch (ClassNotFoundException e) { LOGGER.error("can not load jdbc driver", e); } }
 /** * 获取数据库连接 * * @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; }
 /** * 关闭数据库连接 * @param conn */ public static void closeConnection(Connection conn) { if(conn != null) { try { conn.close(); } catch (SQLException e) { LOGGER.error("close connection failure", e); } } }
 /** * 获取数据库下的所有表名 */ public static List<String> getTableNames() { List<String> tableNames = new ArrayList<>(); Connection conn = getConnection(); ResultSet rs = null; try { //获取数据库的元数据 DatabaseMetaData db = conn.getMetaData(); //从元数据中获取到所有的表名 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; }
 /** * 获取表中所有字段名称 * @param tableName 表名 * @return */ public static List<String> getColumnNames(String tableName) { List<String> columnNames = new ArrayList<>(); //与数据库的连接 Connection conn = getConnection(); PreparedStatement pStemt = null; String tableSql = SQL + tableName; try { pStemt = conn.prepareStatement(tableSql); //结果集元数据 ResultSetMetaData rsmd = pStemt.getMetaData(); //表列数 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; }
 /** * 获取表中所有字段类型 * @param tableName * @return */ public static List<String> getColumnTypes(String tableName) { List<String> columnTypes = new ArrayList<>(); //与数据库的连接 Connection conn = getConnection(); PreparedStatement pStemt = null; String tableSql = SQL + tableName; try { pStemt = conn.prepareStatement(tableSql); //结果集元数据 ResultSetMetaData rsmd = pStemt.getMetaData(); //表列数 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; }
 /** * 获取表中字段的所有注释 * @param tableName * @return */ public static List<String> getColumnComments(String tableName) { List<String> columnTypes = new ArrayList<>(); //与数据库的连接 Connection conn = getConnection(); PreparedStatement pStemt = null; String tableSql = SQL + tableName; List<String> columnComments = new ArrayList<>();//列名注释集合 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)); } }}

在运行代码之前，先将数据库配置进行修改，再运行代码就可以获取数据库表的详细结构了。

后续可以以此为基础写一个通过表结构生成实体、接口、映射文件的简单代码生成器。减少ssm项目开发中编码工作。

原文链接：https://www.cnblogs.com/zuidongfeng/p/7895090.html

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