JDBC DbUtils

package demo;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DbUtil {
private static String url = “jdbc:mariadb://localhost:3306/test?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC”;
private static String username = “test”;
private static String password = “test”;

public static Connection getConnection() {
    Connection conn = null;
    try {
        Class.forName("org.mariadb.jdbc.Driver");
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
    try {
        conn = DriverManager.getConnection(url, username, password);
    } catch (SQLException e) {
        e.printStackTrace();
    }
    return conn;
}

}
dao类
DbUtils核心的CURD功能都在这里。

package demo;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;

public class UserDao {

/**
 * 查询所有用户
 * @return
 */
public List findAll(){
     //创建连接
    Connection conn = DbUtil.getConnection();
    //创建SQL执行工具
    QueryRunner queryRunner = new QueryRunner();
    List list = null;
    try {
        //执行SQL查询，并获取结果
        //BeanListHandler 映射多个对象
        list = queryRunner.query(conn, "select * from user", new BeanListHandler<>(User.class));
    } catch (SQLException e) {
        e.printStackTrace();
    }
    //关闭数据库连接
    DbUtils.closeQuietly(conn);
    return list;
}

/**
 * 保存用户
 * @param user
 */
public void save(User user) {
    Connection conn = DbUtil.getConnection();
    //创建SQL执行工具
    QueryRunner queryRunner = new QueryRunner();
    int rows = 0;
    try {
        //执行SQL插入
        rows = queryRunner.update(conn, "INSERT INTO user(name, age,imgurl) VALUES(?,?,?)",
                new Object[] {user.getName(),user.getAge(),user.getImgurl()});
        //new Object[] {user.getName(),user.getAge(),user.getImgurl()} 设置参数
    } catch (SQLException e) {
        e.printStackTrace();
    }
    //关闭数据库连接
    DbUtils.closeQuietly(conn);
}

/**
 * 查找一个用户
 * @param id
 * @return
 */
public User findOne(int id) {
     //创建连接
    Connection conn = DbUtil.getConnection();
    //创建SQL执行工具
    QueryRunner queryRunner = new QueryRunner();
    User user = new User();
    try {
        //执行SQL查询，并获取结果  
        //BeanHandler 映射成一个对象
        user = queryRunner.query(conn, "select * from user where id=?", new BeanHandler<>(User.class),
                new Object[] {id});
    } catch (SQLException e) {
        e.printStackTrace();
    }
    //关闭数据库连接
    DbUtils.closeQuietly(conn);
    return user;
}

/**
 * 更新用户
 * @param user
 */
public void update(User user) {
    Connection conn = DbUtil.getConnection();
    //创建SQL执行工具
    QueryRunner queryRunner = new QueryRunner();
    int rows = 0;
    try {
        //执行SQL插入
        rows = queryRunner.update(conn, "update user set name=?,age=?,imgurl=? where id=?",
                new Object[] {user.getName(),user.getAge(),user.getImgurl(),user.getId()});
        //new Object[] {user.getName(),user.getAge(),user.getImgurl()} 设置参数
    } catch (SQLException e) {
        e.printStackTrace();
    }
    //关闭数据库连接
    DbUtils.closeQuietly(conn);
}

/**
 * 根据ID删除用户
 * @param id
 */
public void delete(int id) {
    Connection conn = DbUtil.getConnection();
    //创建SQL执行工具
    QueryRunner queryRunner = new QueryRunner();
    int rows = 0;
    try {
        //执行SQL插入
        rows = queryRunner.update(conn,"delete from user where id=?", new Object[] {id});
    } catch (SQLException e) {
        e.printStackTrace();
    }
    //关闭数据库连接
    DbUtils.closeQuietly(conn);
}

}
QueryRunner执行SQL语句的方法原型：public int update(Connection conn, String sql,Object… params) throws SQLException

它有三个参数，一个是连接，一个是SQL语句，一个是SQL语句中的参数。

其中参数是一个多参数对象，数据类型为Object，实例化这个多值参数的对象时应该这样：

new Object[] {user.getName(),user.getAge(),user.getImgurl()} //设置参数package demo;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DbUtil {
private static String url = “jdbc:mariadb://localhost:3306/test?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC”;
private static String username = “test”;
private static String password = “test”;

public static Connection getConnection() {
    Connection conn = null;
    try {
        Class.forName("org.mariadb.jdbc.Driver");
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
    try {
        conn = DriverManager.getConnection(url, username, password);
    } catch (SQLException e) {
        e.printStackTrace();
    }
    return conn;
}

}
dao类
DbUtils核心的CURD功能都在这里。

package demo;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;

public class UserDao {

/**
 * 查询所有用户
 * @return
 */
public List findAll(){
     //创建连接
    Connection conn = DbUtil.getConnection();
    //创建SQL执行工具
    QueryRunner queryRunner = new QueryRunner();
    List list = null;
    try {
        //执行SQL查询，并获取结果
        //BeanListHandler 映射多个对象
        list = queryRunner.query(conn, "select * from user", new BeanListHandler<>(User.class));
    } catch (SQLException e) {
        e.printStackTrace();
    }
    //关闭数据库连接
    DbUtils.closeQuietly(conn);
    return list;
}

/**
 * 保存用户
 * @param user
 */
public void save(User user) {
    Connection conn = DbUtil.getConnection();
    //创建SQL执行工具
    QueryRunner queryRunner = new QueryRunner();
    int rows = 0;
    try {
        //执行SQL插入
        rows = queryRunner.update(conn, "INSERT INTO user(name, age,imgurl) VALUES(?,?,?)",
                new Object[] {user.getName(),user.getAge(),user.getImgurl()});
        //new Object[] {user.getName(),user.getAge(),user.getImgurl()} 设置参数
    } catch (SQLException e) {
        e.printStackTrace();
    }
    //关闭数据库连接
    DbUtils.closeQuietly(conn);
}

/**
 * 查找一个用户
 * @param id
 * @return
 */
public User findOne(int id) {
     //创建连接
    Connection conn = DbUtil.getConnection();
    //创建SQL执行工具
    QueryRunner queryRunner = new QueryRunner();
    User user = new User();
    try {
        //执行SQL查询，并获取结果  
        //BeanHandler 映射成一个对象
        user = queryRunner.query(conn, "select * from user where id=?", new BeanHandler<>(User.class),
                new Object[] {id});
    } catch (SQLException e) {
        e.printStackTrace();
    }
    //关闭数据库连接
    DbUtils.closeQuietly(conn);
    return user;
}

/**
 * 更新用户
 * @param user
 */
public void update(User user) {
    Connection conn = DbUtil.getConnection();
    //创建SQL执行工具
    QueryRunner queryRunner = new QueryRunner();
    int rows = 0;
    try {
        //执行SQL插入
        rows = queryRunner.update(conn, "update user set name=?,age=?,imgurl=? where id=?",
                new Object[] {user.getName(),user.getAge(),user.getImgurl(),user.getId()});
        //new Object[] {user.getName(),user.getAge(),user.getImgurl()} 设置参数
    } catch (SQLException e) {
        e.printStackTrace();
    }
    //关闭数据库连接
    DbUtils.closeQuietly(conn);
}

/**
 * 根据ID删除用户
 * @param id
 */
public void delete(int id) {
    Connection conn = DbUtil.getConnection();
    //创建SQL执行工具
    QueryRunner queryRunner = new QueryRunner();
    int rows = 0;
    try {
        //执行SQL插入
        rows = queryRunner.update(conn,"delete from user where id=?", new Object[] {id});
    } catch (SQLException e) {
        e.printStackTrace();
    }
    //关闭数据库连接
    DbUtils.closeQuietly(conn);
}

}
QueryRunner执行SQL语句的方法原型：public int update(Connection conn, String sql,Object… params) throws SQLException

它有三个参数，一个是连接，一个是SQL语句，一个是SQL语句中的参数。

其中参数是一个多参数对象，数据类型为Object，实例化这个多值参数的对象时应该这样：

new Object[] {user.getName(),user.getAge(),user.getImgurl()} //设置参数