利用jdbc简单封装一个小框架（类似DBUtils）

Posted 2020-10-09 jjkang

利用jdbc写的一个类似DBUtils的框架

package com.jdbc.orm.dbutils;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

import com.jdbc.orm.handler.ResultsetHand;

/**
 * 
 * 功能描述：基于jdbc自己封装的orm小框架
 * 
 */
public class DBUtils {
    public static String username;
    public static String password;
    public static String driverClass;
    public static String url;

    public static Connection connection;
    public static PreparedStatement statement;
    public static ResultSet rs;

    static {
    Properties properties = new Properties();
    InputStream in = DBUtils.class.getClassLoader().getResourceAsStream("db.properties");
    try {
        properties.load(in);// 加载数据库的配置文件
        driverClass = properties.get("jdbc.driverclass").toString();
        username = properties.get("jdbc.username").toString();
        password = properties.get("jdbc.password").toString();
        url = properties.get("jdbc.url").toString();
    } catch (IOException e) {
        e.printStackTrace();
        try {
        Class.forName(driverClass);// 加载数据库的驱动程序
        } catch (ClassNotFoundException e1) {
        e1.printStackTrace();
        }
    }
    }

    /**
     * 
     * 功能 ：为SQL语句设置参数
     * 
     * @param sql
     *            输入的sql语句
     * @param params
     *            需要的参数
     * @throws SQLException
     */
    public static void setParams(String sql, Object... params) throws SQLException {
    connection = DriverManager.getConnection(url, username, password);
    statement = connection.prepareStatement(sql);
    if ( params != null && params.length > 0) {
        for (int i = 0; i < params.length; i++) {
        statement.setObject(i + 1, params[i]);
        }
    }
    }

    /**
     * 
     * @功能 ：根据ID查询实体
     * @param sql
     * @param id
     * @return 返回结果集
     * @throws Exception
     */
    public static ResultSet queryBeanById(String sql, int id) throws Exception {
    setParams(sql, id);
    return statement.executeQuery();
    }

    /**
     * 
     * @功能 ：查询功能
     * @param sql
     * @param params
     * @return 将查询到的结果映射到一个实体中返回
     * @throws SQLException
     */
    public static Object query(String sql, ResultsetHand rsh, Object... params) throws SQLException {
    setParams(sql, params);
    ResultSet rs = statement.executeQuery();
    return rsh.handler(rs);
    }

    /**
     * 
     * @功能 ：增删改功能
     * @param sql
     * @param params
     * @throws SQLException
     */
    public static int update(String sql, Object... params) throws SQLException {
    setParams(sql, params);
    return statement.executeUpdate();
    }

}

package com.jdbc.orm.handler;

import java.lang.reflect.Field;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;

/**
 * @描述 : 将查询到的结果映射到集合中
 * @author 作者 jjkang
 * @version 创建时间：2017年10月6日 下午8:04:46
 */
@SuppressWarnings("rawtypes")
public class BeanListHandler implements ResultsetHand {
    private Class clazz;

    public BeanListHandler(Class clazz) {
    this.clazz = clazz;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Object handler(ResultSet rs) {
    List list = new ArrayList();
    try {

        ResultSetMetaData metaData = rs.getMetaData();
        int columnCount = metaData.getColumnCount();
        while (rs.next()) {
        Object bean = clazz.newInstance();
        for (int i = 0; i < columnCount; i++) {
            Object object = rs.getObject(i + 1);
            String name = metaData.getColumnName(i + 1);
            Field field = clazz.getDeclaredField(name);
            field.setAccessible(true);
            field.set(bean, object);
        }
        list.add(bean);
        }
        return list;
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
    }

}

package com.jdbc.orm.handler;

import java.lang.reflect.Field;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;

/**
 * @描述 :将查询的结果映射到实体中
 * @author 作者 E-mail: [email protected]
 * @version 创建时间：2017年10月6日 下午5:45:04
 */
public class BeanHandler implements ResultsetHand {

    private Class clazz;// 将结果映射到的实体

    public BeanHandler(Class clazz) {
    this.clazz = clazz;
    }

    @Override
    public Object handler(ResultSet rs) {
    try {
        if (!rs.next()) {
        return null;
        }
        Object bean = clazz.newInstance();
        ResultSetMetaData metaData = rs.getMetaData();
        int columnCount = metaData.getColumnCount();
        for (int i = 0; i < columnCount; i++) {
        String name = metaData.getColumnName(i + 1);// 得出每一列的列名
        Object value = rs.getObject(i + 1);// 得到每一列的值
        Field field = clazz.getDeclaredField(name);// 利用反射，根据列名得到属性对象
        field.setAccessible(true);
        field.set(bean, value);
        }
        return bean;
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
    }
}

package com.jdbc.orm.junit;

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

import org.junit.Test;

import com.jdbc.orm.bean.Student;
import com.jdbc.orm.dbutils.DBUtils;
import com.jdbc.orm.handler.BeanHandler;
import com.jdbc.orm.handler.BeanListHandler;

/** 
* 描述 : 测试DBUtils
* @version 创建时间：2017年10月6日 下午2:40:45 
*/
public class TestDBUtils {
    DBUtils dbUtils = new DBUtils();
    @Test
    public void test(){
    System.out.println(dbUtils.driverClass);
    System.out.println(dbUtils.password);
    System.out.println(dbUtils.url);
    System.out.println(dbUtils.username);
    }
    
    @Test
    public void testSetParams() throws SQLException{
    String sql = "select name from student where id = ?";
    Object params[] = {1};
    DBUtils.setParams(sql, params);
    }
    @Test
    public void testQueryBeanById() throws Exception{
    String sql = "select id,name,chinese,english,math from student where id = ?";
    ResultSet rs=dbUtils.queryBeanById(sql, 1);
    Student student = new Student();
    
    while(rs.next()){
        student.setId(rs.getInt(1));
        student.setName(rs.getString(2));
        student.setChinese(rs.getDouble(3));
        student.setEnglish(rs.getDouble(4));
        student.setMath(rs.getDouble(5));
    }
    System.out.println(student);
    }
    
    @Test
    public void testUpdate() throws SQLException{
    String sql = "update student set name=? where id =?";
    Object[] params = {"李晓明",1};
    int rows = dbUtils.update(sql, params);
    System.out.println(rows);
    }
    
    @Test
    public void testQuery() throws Exception{
    String sql = "select id,name,chinese,english,math from student where id = ?";
    Student student = new Student();
    student = (Student) dbUtils.query(sql,new BeanHandler(Student.class), 1);
    System.out.println(student);
    }
    @Test
    public void testQuery1() throws Exception{
    String sql = "select id,name,chinese,english,math from student";
    List<Student> list = new ArrayList<>();
    list = (List<Student>) dbUtils.query(sql,new BeanListHandler(Student.class), null);
    System.out.println(list.size());
    System.out.println(list);
    }
}