JdbcUtil

转自：https://github.com/ghyg525/util_java_jdbc

 JdbcUtil.java

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;

/**
 * 简单封装数据库工具类
 * 查询返回结果有数组, List, Map
 * 其他类型语句都调用execute
 * @author YJ
 */
public class JdbcUtil {

    /**
     * 查询返回String二维数组
     * @param sql
     * @param args
     * @return
     */
    public static String[][] queryForArray(String sql, Object... args) {
        Connection conn = null;
        PreparedStatement stmt = null;
        ResultSet rs = null;
        String[][] result = null;
        try {
            conn = getConnection();
            stmt = conn.prepareStatement(sql,
                    ResultSet.TYPE_SCROLL_INSENSITIVE,
                    ResultSet.CONCUR_READ_ONLY);
            if (args != null) {
                for (int i = 0; i < args.length; i++) {
                    stmt.setObject(i + 1, args[i]);
                }
            }
            rs = stmt.executeQuery();
            rs.last();
            int rows = rs.getRow();
            rs.beforeFirst();
            ResultSetMetaData rsmd = rs.getMetaData();
            int cols = rsmd.getColumnCount();
            result = new String[rows+1][cols];
            for (int i = 0; i < cols; i++) {
                result[0][i] = rsmd.getColumnName(i + 1);
            }
            int currentRow = 1;
            while (rs.next()) {
                for (int i = 0; i < cols; i++) {
                    result[currentRow][i] = rs.getObject(i + 1).toString();
                }
                currentRow++;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (rs != null)
                    rs.close();
                if (stmt != null)
                    stmt.close();
                if (conn != null)
                    conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return result;
    }

    /**
     * 查询返回List类型
     * @param sql
     * @param args
     * @return 多条记录的List集合
     */
    public static List<Map<String, Object>> queryForList(String sql, Object... args) {
        Connection conn = null;
        PreparedStatement stmt = null;
        ResultSet rs = null;
        List<Map<String, Object>> result = new ArrayList<Map<String, Object>>();
        try {
            conn = getConnection();
            stmt = conn.prepareStatement(sql);
            if (args != null) {
                for (int i = 0; i < args.length; i++) {
                    stmt.setObject(i + 1, args[i]);
                }
            }
            rs = stmt.executeQuery();
            ResultSetMetaData rsmd = rs.getMetaData();
            int cols = rsmd.getColumnCount();
            String[] colNames = new String[cols];
            for (int i = 0; i < cols; i++) {
                colNames[i] = rsmd.getColumnName(i + 1);
            }
            while (rs.next()) {
                Map<String, Object> row = new LinkedHashMap<String, Object>();
                for (int i = 0; i < cols; i++) {
                    row.put(colNames[i], rs.getObject(i + 1));
                }
                result.add(row);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (rs != null)
                    rs.close();
                if (stmt != null)
                    stmt.close();
                if (conn != null)
                    conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return result;
    }

    /**
     * 查询返回Map类型 当确定返回结果唯一时调用
     * @param sql
     * @param args
     * @return 一条记录的Map
     */
    public static Map<String, Object> queryForMap(String sql, Object... args) {
        List<Map<String, Object>> result = queryForList(sql, args);
        Map<String, Object> row = null;
        if (result.size() == 1) {
            row = result.get(0);
            return row;
        } else {
            return null;
        }
    }

    /**
     * 执行除查询外(增加/删除/修改)
     * @param sql
     * @param args
     * @return 是否执行成功
     */
    public static boolean execute(String sql, Object... args) {
        Connection conn = null;
        PreparedStatement stmt = null;
        boolean result = true;
        try {
            conn = getConnection();
            stmt = conn.prepareStatement(sql);
            if (args != null) {
                for (int i = 0; i < args.length; i++) {
                    stmt.setObject(i + 1, args[i]);
                }
            }
            stmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
            result = false;
        } finally {
            try {
                if (stmt != null)
                    stmt.close();
                if (conn != null)
                    conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return result;
    }


    /**
     * 获得数据库连接
     * @return
     */
    private static Connection getConnection() {
        Connection conn = null;
        try {
            Class.forName(getProperties().getProperty("driver"));
            conn = DriverManager.getConnection(getProperties().getProperty("url"),
                    getProperties().getProperty("username"), getProperties().getProperty("password"));
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }

    /**
     * 读取配置文件信息
     * @return
     */
    private static Properties getProperties(){
        Properties properties = new Properties();
        try {
            properties.load(JdbcUtil.class.getResourceAsStream("/jdbc.properties"));
        } catch (IOException e) {
            e.printStackTrace();
        }
        return properties;
    }


}

jdbc.properties

url=jdbc:mysql://localhost:3306/esweb
driver=com.mysql.jdbc.Driver
username=root
password=root

测试：

public class JdbcMysql {

    public static void main(String[] args) {

        String sql1 = "select * from screen_201808";
        String sql2 = "select * from screen_201808 where id = ?";
        System.out.println(JdbcUtil.queryForArray(sql1)[1][1]);
        System.out.println(JdbcUtil.queryForList(sql1));
        System.out.println(JdbcUtil.queryForMap(sql2,1));
    }
}

 参考文档：

https://github.com/ghyg525/util_java_jdbc

https://www.shiyanlou.com/courses/110