Java数据库连接（JDBC）、JDBC连接池（c3p0）、MyBatis分别如何使用？如何连接数据库？

一、JDBC的使用

第一步：导入jar包（mysql-connector-java.jar）

第二步：jdbc就是一个连接数据库工具，分为几个步骤

1. 加载驱动
2. 创建连接
3. 创建statement
4. 执行语句

第三步：编写代码实现

public class JdbcTest {

    public static void main(String[] args) throws ClassNotFoundException, SQLException {

       Class.forName("com.mysql.jdbc.Driver");

       String url = "jdbc:mysql://localhost:3306/book";

       String user = "root";

       String password = "123456";

       Connection connection = DriverManager.getConnection(url, user, password);

       Statement statement = connection.createStatement();

       String sql = "select * from book_info where book_id=1";

       ResultSet result = statement.executeQuery(sql);

       while(result.next()) {

           System.out.println(result.getString(1)

           +"  "+result.getString(2)

           +"  "+result.getString(3)

           +"  "+result.getString(4)

           +"  "+result.getString(5)

           +"  "+result.getString(6)

           +"  "+result.getString(7)

           +"  "+result.getString(8)

           +"  "+result.getString(9)

           +"  "+result.getString(10)

           +"  "+result.getString(11)

           );

       }

       result.close();

       statement.close();

    }

二、c3p0的使用

第一步：导入jar包mysql-connector-java.jar和c3p0.jar

第二步：参数配置

<?xml version="1.0" encoding="UTF-8"?>

<c3p0-config>

    <default-config>

       <property name="user">root</property>

       <property name="password">123456</property>

       <property name="jdbcUrl">jdbc:mysql://localhost:3306/book</property>

       <property name="driverClass">com.mysql.jdbc.Driver</property>

    </default-config>

</c3p0-config>

第三步：编写代码实现

package com.xc.c3p0;

import java.sql.Connection;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class C3p0 {

       public static void main(String[] args) throws SQLException {

              DataSource source = new ComboPooledDataSource();

              Connection connection = source.getConnection();

              Statement statement = connection.createStatement();

              String sql = "select * from book_info";

              ResultSet result = statement.executeQuery(sql);

              while(result.next()) {

                     System.out.println(result.getString(1)

                                   +"  "+result.getString(2)

                                   +"  "+result.getString(3)

                                   +"  "+result.getString(4)

                                   +"  "+result.getString(5)

                                   +"  "+result.getString(6)

                                   +"  "+result.getString(7)

                                   +"  "+result.getString(8)

                                   +"  "+result.getString(9)

                                   +"  "+result.getString(10)

                                   +"  "+result.getString(11)

                                   );

                            }

                            result.close();

                            statement.close();

       }

}

三、MyBatis的使用

注：此处不在详细讲解操作步骤，而是主要整理技术演进，详细操作流程请参考其他博主的教程

第一步：项目中需要导入下图中三个jar包

第二步：编写配置文件以及测试代码

1、db.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/book
username=root
password=123456

2、mybatis-config.xml

"<configuration>
 <properties resource=""db.properties""/>
 <environments default=""development"">
  <environment id=""development"">
   <transactionManager type=""JDBC""></transactionManager>
   <dataSource type=""POOLED"">
    <property name=""driver"" value=""${driver}""></property>
    <property name=""url"" value=""${url}""></property>
    <property name=""username"" value=""${username}""></property>
    <property name=""password"" value=""${password}""></property>
   </dataSource>
  </environment>
 </environments>
 <mappers>
  <mapper resource = ""com/xc/dao/impl/UserMapper.xml""></mapper>
 </mappers>
</configuration>
"

3、UserMapper.xml

"<mapper namespace=""com.xc.dao.impl.UserMapper"">
 <select id=""count"" resultType=""int"">
  select count(1) as count from users
 </select>
</mapper>
"

4、UserMapperTest.java

public class UserMapperTest {　　
　　public static void main(String[] args) throws SQLException, FileNotFoundException {
　　　　String resource = "D:\\Eclipse_WorkSpace\\MavenProject\\WebMavenDemo01\\src\\main\\resources\\mybatis-config.xml";
　　　　InputStream in = new FileInputStream(resource);
　　　　SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
　　　　int count = 0;
　　　　SqlSession sqlSession = null;
　　　　sqlSession = factory.openSession();
　　　　//执行sql
　　　　count = sqlSession.selectOne("com.xc.dao.impl.UserMapper.count");
　　　　System.out.println(count);
　　　　sqlSession.close();
　　}
}

四、总结

MyBatis 是一款优秀的持久层框架，它支持定制化 SQL、存储过程以及高级映射。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以使用简单的 XML 或注解来配置和映射原生信息，将接口和 Java 的 POJOs(Plain Old Java Objects,普通的 Java对象)映射成数据库中的记录。