Dbutils工具类的使用

　C：使用Dbutils的具体步骤

　　a：创建QueryRunner对象　

QueryRunner queryRunner = new QueryRunner();

　　b：调用QueryRunner对象的方法执行相关操作，给QueryRunner对象传递参数：connection，sql，具体的策略对象;，条件参数

public void insert(Student student) {
        sql = "insert into student(name,clazz,grade) values(?,?,?)";
        try {
            //JDBCTools.getConnection()：数据库连接
            //sql：数据库查询sql语句
            //student.getName():需要的参数，参数与sql中的参数的数量保持一致
            queryRunner.update(JDBCTools.getConnection(),sql,student.getName(),student.getClazz(),student.getGrade());
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

public Student findById(int id) {
        sql = " select * from student where id = ?";
        Student student = null;
        try {
            student = queryRunner.query(JDBCTools.getConnection(),sql,new BeanHandler<Student>(Student.class),id);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return student;
    }

策略对象

• BeanHandler：把单行的结果集封装成javabean对象，返回值是ResultSetHandler，该方法用于将单行结果集封装成javabean对象，对象是通过反射完成创建的

ResultSetHandler<javabean类型> rsh = new BeanHandler<javabean类型>(javabean.class);

• BeanListHandler：将多行结果集封装成对象，并将对象添加到list集合中

 List<javaBean类型> list = <List<javaBean类型>> new BeanListHandler<javaBean类型>(javaBean.class);

• MapHandler：将单行的结果集封装到一个map集合中，map集合中的建是表中的列名称，值对应表的列值。

Map <String,Object> map = new MapHandler();

• MapListHandler：用于多行结果集的处理，把每行的结果封装成一个map，最后把所有的map都放到一个集合中，返回的是一个list集合，list集合中存放的是map集合。

  List<Map<String,Object>> listmap = new MapListHandler();

• ColumnHandler：本方法用于互殴去单列，单行或者多行的数据

List<Object> nameList = new ColumnHandler();

• ScalarHandler：用户处理单行、单列的数据，多用于聚合函数的查询。注意：当聚合函数涉及到数字类型的时候，要注意返回值类型的转换，若使用Integer或者Long类型的时候，容易出现数据无法存储的时候，所以使用Number（这个是所有数字数据类型的父类），对外提供了Number.intValue()和Number.longValue()等方法。

ResultSetHandler resultSetHandler = new ScalarHandler();

C：具体的实现代码

　　a：JavaBean对象

package com.dreambamboo.entity;

public class Student {
    private int id;
    private String name;
    private String grade;
    private String clazz;

    public Student(int id, String name, String grade, String clazz) {
        this.id = id;
        this.name = name;
        this.grade = grade;
        this.clazz = clazz;
    }

    public Student() {
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGrade() {
        return grade;
    }

    public void setGrade(String grade) {
        this.grade = grade;
    }

    public String getClazz() {
        return clazz;
    }

    public void setClazz(String clazz) {
        this.clazz = clazz;
    }

    public Student(String name, String grade, String clazz) {
        this.name = name;
        this.grade = grade;
        this.clazz = clazz;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name=‘" + name + ‘\‘‘ +
                ", grade=‘" + grade + ‘\‘‘ +
                ", clazz=‘" + clazz + ‘\‘‘ +
                ‘}‘;
    }
}

　　b：dao接口

package com.dreambamboo.dao;

import com.dreambamboo.entity.Student;

import java.util.List;


public interface StudentDao {
    /**
     * 添加学生信息
     * @param student
     */
    public void insert(Student student);

    /**
     * 更新学生信息
     * @param student
     */
    public void update(Student student);

    /**
     * 删除学生信息
     * @param id
     */
    public void delete(int id);

    /**
     * 根据学生编号查询学生信息
     * @param id
     * @return
     */
    public Student findById(int id);

    /**
     * 查询所有学生信息
     * @return
     */
    public List<Student> findAll();

    /**
     * 查询学生总数
     * @return
     */
    public int studentCount();
}

　　c：dao接口实现类

package com.dreambamboo.dao.impl;

import com.dreambamboo.dao.StudentDao;
import com.dreambamboo.entity.Student;
import com.dreambamboo.util.JDBCTools;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.ResultSetHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

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

public class StudentDaoImpl implements StudentDao {
    private QueryRunner queryRunner = null;//查询运行器
    public StudentDaoImpl(){
        queryRunner = new QueryRunner();
    }
    String sql = null;
    @Override
    public void insert(Student student) {
        sql = "insert into student(name,clazz,grade) values(?,?,?)";
        try {
            //JDBCTools.getConnection()：数据库连接
            //sql：数据库查询sql语句
            //student.getName():需要的参数，参数与sql中的参数的数量保持一致
            queryRunner.update(JDBCTools.getConnection(),sql,student.getName(),student.getClazz(),student.getGrade());
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void update(Student student) {
        sql = " update student set name = ? ,clazz = ?,grade = ? where id = ?";
        try {
            queryRunner.update(JDBCTools.getConnection(),sql,student.getName(),student.getClazz(),student.getGrade(),student.getId());
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void delete(int id) {
        sql = "delete from student where id = ?";
        try {
            queryRunner.update(JDBCTools.getConnection(),sql,id);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public Student findById(int id) {
        sql = " select * from student where id = ?";
        Student student = null;
        try {
            student = queryRunner.query(JDBCTools.getConnection(),sql,new BeanHandler<Student>(Student.class),id);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return student;
    }

    @Override
    public List<Student> findAll() {
        sql = "select * from student";
        List<Student> list = null;
        try {
            list = queryRunner.query(JDBCTools.getConnection(),sql,new BeanListHandler<>(Student.class));
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return list;
    }
    @Override
    public int studentCount() {
        sql = "select count(id) from student";
        int count = 0;
        try {
            count =  queryRunner.query(JDBCTools.getConnection(),sql,new ScalarHandler<Integer>());

        } catch (SQLException e) {
            e.printStackTrace();
        }
        return count;
    }
}

　　d：数据库接口连接工具类

package com.dreambamboo.util;



import java.sql.*;
import java.util.ResourceBundle;

/**
 * 数据库操作工具类
 */
public class JDBCTools {
    private static String URL;
    private static String USERNAME;
    private static String PASSWORD;
    private static String DRIVER;

    private static ResourceBundle resourceBundle = ResourceBundle.getBundle("com.dreambamboo.util.db-config");

    private JDBCTools(){

    }

    /**
     * 使用静态代码块加载驱动程序
     *      防止重复代码，使用静态代码块在类加载的时候只会执行一次
     */
    static {
        URL = resourceBundle.getString("jdbc.url");
        USERNAME = resourceBundle.getString("jdbc.username");
        PASSWORD = resourceBundle.getString("jdbc.password");
        DRIVER = resourceBundle.getString("jdbc.driver");
    }

    /**
     * 获取数据库连接
     * @return
     */
    public static Connection getConnection(){
        Connection connection = null;
        try {
            connection = DriverManager.getConnection(URL,USERNAME,PASSWORD);
        } catch (SQLException e) {
            e.printStackTrace();
            System.out.println("获取连接失败");
        }
        return connection;
    }

    /**
     * 关闭数据库连接资源
     * @param connection    数据库连接
     * @param statement     数据库会话语句
     * @param resultSet     数据库查询结果集
     */
    public static void release(Connection connection, Statement statement, ResultSet resultSet){
        try {
            if (connection != null) {
                connection.close();
            }
            if (statement != null) {
                statement.close();
            }
            if (resultSet != null) {
                resultSet.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

}

　　e：数据库配置文件

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

　　f：测试代码

package com.dreambamboo.test;

import com.dreambamboo.dao.StudentDao;
import com.dreambamboo.dao.impl.StudentDaoImpl;
import com.dreambamboo.entity.Student;

import java.util.List;

public class Test {
    public static void main(String[] args) {
        StudentDao studentDao = new StudentDaoImpl();
        //studentDao.insert(new Student("孙悟空","高三年级","五班"));
        //studentDao.update(new Student(14,"孙悟空111","高三年级","十一班"));
        //studentDao.delete(14);
        List<Student> list = studentDao.findAll();
        for (Student st : list) {
            System.out.println(st.getId() + "===>>>" + st.getName() + "===>>>>" + st.getClazz() + "===>>> "+ st.getGrade());
        }
    }
}

 三、自定义的Dbutils工具类

Dbutils工具类的使用

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