java獲取mysql數據庫表、字段、字段類型、字段注釋

　　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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