java数据库工具--DBUtils

dome gitub :https://github.com/shimingda/java-dome

概述

DBUtils是Java编程中的数据库操作实用工具，小巧简单实用。
DBUtils封装了对JDBC的操作，简化了JDBC操作，可以少写代码。

DBUtils三个核心功能介绍

QueryRunner中提供对sql语句操作的API
ResultSetHandler接口，用于定义select操作后，怎样封装结果集
DBUtils类，它就是一个工具类，定义了关闭资源与事务处理的方法

QueryRunner核心类

• QueryRunner(DataSourcr ds),提供数据源（连接池），DbUtils底层自动维护连接connection
• update（String sql，Obj…params），执行更新数据
• query（String sql，ResultSetHandlerrsh,Object…panrams)，执行查询

ResultSetHandler结果集处理类

• ArrayHandler：适合取1条记录，把结果集中的第一行数据转成对象数组。
• ArrayListHandler：适合取多条记录，把结果集中的每一行数据都转成一个对象数组，再存放到List中。
• BeanHandler：将结果集中的第一行数据封装到一个对应的JavaBean实例中（把每条记录封装成对象，适合取一条记录）
• BeanListHandler：将结果集中的每一行数据都封装到一个对应的JavaBean实例中，存放到List里。//重点
• MapHandler：将结果集中的第一行数据封装到一个Map里，key是列名，value就是对应的值。//重点
• MapListHandler：将结果集中的每一行数据都封装到一个Map里，然后再存放到List
• ColumnListHandler：将结果集中某一列的数据存放到List中。
• KeyedHandler(name)：将结果集中的每一行数据都封装到一个Map里(List
• ScalarHandler:将结果集第一行的某一列放到某个对象中。//重点

基础

package dome.base;

import org.apache.commons.dbcp2.BasicDataSource;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.DriverManager;

/**
 * 数据配置
 * @author  Somin
 */
public class DBConf
{
   static final String JDBC_DRIVER = "com.mysql.cj.jdbc.Driver";
   static final String DB_URL = "jdbc:mysql://localhost:3306/test?serverTimezone=UTC&characterEncoding=utf-8";

   static final String USER = "root";
   static final String PASS = "1234";

   public static Connection getConnection(){
      try
      {
         Class.forName(DBConf.JDBC_DRIVER);
         return DriverManager.getConnection(DBConf.DB_URL, DBConf.USER, DBConf.PASS);
      }
      catch (Exception e)
      {
         System.out.println("databases connection error");
         return null;
      }
   }
   public static DataSource getDataSource()
   {
      BasicDataSource basicDataSource=new BasicDataSource();
      basicDataSource.setDriverClassName(JDBC_DRIVER);
      basicDataSource.setUsername(USER);
      basicDataSource.setPassword(PASS);
      basicDataSource.setUrl(DB_URL);
      return basicDataSource;
   }
}

package dome.base;

/**
 * 数据库实体类
 * @author  Somin
 */
public class User
{
   public int id;
   public String name;
   public int age;

   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 int getAge()
   {
      return age;
   }

   public void setAge(int age)
   {
      this.age = age;
   }
}

import dome.base.DBConf;
import dome.base.User;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.ResultSetHandler;
import org.apache.commons.dbutils.handlers.*;
import org.junit.Before;
import org.junit.Ignore;
import org.junit.Test;

import java.sql.Connection;
import java.util.Arrays;
import java.util.List;
import java.util.Map;

/**
 * base test
 * @author Somin
 */
public class BaseTest
{

   QueryRunner queryRunner = new QueryRunner();
   Connection conn= null;
   @Before
   public void init()
   {
      conn= DBConf.getConnection();
   }

   @Test
   @Ignore
   public void insertTest() throws  Exception
   {
      String sql = "INSERT INTO user(name, age) VALUES(?,?)";

      Object[] objectArr= queryRunner.insert(conn, sql, new ArrayHandler(), "root", 18);
      System.out.println("数组长度：" + objectArr.length + "；第0个元素的值：" +objectArr[0]);

      objectArr = queryRunner.insert(conn, sql, new ArrayHandler(), "test", 19);
      System.out.println("数组长度：" + objectArr.length + "；第0个元素的值：" +objectArr[0]);
   }

   @Test
   @Ignore
   public void queryBeanTest() throws Exception
   {
      ResultSetHandler resultSetHandler=new BeanHandler(User.class);
      String sql ="SELECT * FROM user where id =?";
      User user=queryRunner.query(conn,sql,resultSetHandler,1);
      System.out.println("ID:"+user.getId()+",name:"+user.getName());

      ResultSetHandler> resultSetHandlers=new BeanListHandler(User.class);
      String sqlList="SELECT * FROM user";
      List users=queryRunner.query(conn,sqlList,resultSetHandlers);
      users.forEach(u->{
         System.out.println("id:"+u.getId()+",name:"+u.getName());
      });
   }

   @Test
   public void queryMapTest() throws Exception
   {
      String sql ="SELECT * FROM user where id =?";
      Map resultMap =    queryRunner.query(conn,sql,new MapHandler(),1);
      System.out.println("获取一条数据："+resultMap);

      String sql2 ="SELECT * FROM user ";
      List> resultMaps = queryRunner.query(conn,sql2,new MapListHandler());
      resultMaps.forEach(result->{
         System.out.println(result);
      });
   }

   @Test
   @Ignore
   public void queryListTest() throws Exception
   {
      String sql="SELECT * FROM user";
      List objects=  queryRunner.query(conn,sql,new ArrayListHandler());
      objects.forEach(object->{
         System.out.println(Arrays.toString(object));
      });
   }
}

进阶

package dome.advanced;

import dome.base.User;
import org.apache.commons.dbutils.handlers.BeanHandler;

import java.sql.ResultSet;
import java.sql.SQLException;

/**
 * 自定义映射
 * @author  Somin
 */
public class UserHandler extends BeanHandler
{
   public UserHandler()
   {
      super(User.class);
   }

   @Override
   public User handle(ResultSet rs) throws SQLException
   {
      return super.handle(rs);
   }
}

import dome.advanced.UserHandler;
import dome.base.DBConf;
import dome.base.User;
import org.apache.commons.dbutils.QueryRunner;
import org.junit.Ignore;
import org.junit.Test;

import java.sql.Connection;

/**
 * advanced test
 * @author Somin
 */
public class AdvancedTest
{
   @Test
   @Ignore
   public void handlerTest() throws Exception
   {
      QueryRunner queryRunner = new QueryRunner();
      Connection conn=DBConf.getConnection();
      String sql ="SELECT * FROM user where id =?";
      User user=queryRunner.query(conn,sql,new UserHandler(),1);
      System.out.println("id:"+user.getId()+",name:"+user.getName());
   }

   @Test
   public void dataSourceTest() throws Exception
   {
      QueryRunner queryRunner=new QueryRunner(DBConf.getDataSource());
      String sql ="SELECT * FROM user where id =?";
      User user=queryRunner.query(sql,new UserHandler(),1);
      System.out.println("id:"+user.getId()+",name:"+user.getName());
   }
}