mybatis框架学习-入门案例，注解方式

与mapper.xml方式配置的不同有

mybatis基于注解的入门案例：

            把AccountMapper.xml移除，在mapper接口的方法上使用@Select注解，并且指定SQL语句

　　　 同时需要在SqlMapConfig.xml中的mapper配置时，使用class属性指定mapper接口的全限定类名。

1.前期mysql准备

create database cong
use cong;
create table account(
    id int primary key auto_increment,
    name varchar(40),
    money float
)character set utf8 collate utf8_general_ci;

insert into account(name,money) values('aaa',1000);
insert into account(name,money) values('bbb',1000);
insert into account(name,money) values('ccc',1000);

2.创建maven项目，导入包

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.cong</groupId>
    <artifactId>mybatis_account_firstDemo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <packaging>jar</packaging>
    <dependencies>
        <!-- mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <!-- 数据库连接 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
    </dependencies>
</project>

2.在src，main，java下创建实体类com.cong.pojo.Account和接口com.cong.mapper.AccountMapper

package com.cong.pojo;

import java.io.Serializable;
public class Account implements Serializable {
    private int id;
    private String name;
    private float money;

    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 float getMoney() {
        return money;
    }

    public void setMoney(float money) {
        this.money = money;
    }

    @Override
    public String toString() {
        return "Account{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", money=" + money +
                '}';
    }
}

AccountMapper是接口

package com.cong.mapper;

import com.cong.pojo.Account;
import org.apache.ibatis.annotations.Select;
import java.util.List;

public interface AccountMapper {
    @Select("select * from account")
    List<Account> findAll();
    @Select("select * from account where id = #{id}")
    Account findById(int id);
}

3.在src，main，resources下创建SqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<!-- mybatis的主配置文件 -->
<configuration>
    <!-- 配置环境 -->
    <environments default="mysql">
        <!-- 配置mysql的环境-->
        <environment id="mysql">
            <!-- 配置事务的类型-->
            <transactionManager type="JDBC"></transactionManager>
            <!-- 配置数据源（连接池） -->
            <dataSource type="POOLED">
                <!-- 配置连接数据库的4个基本信息 -->
                <property name="driver" value="com.mysql.jdbc.Driver"></property>
                <property name="url" value="jdbc:mysql://localhost:3306/cong"/>
                <property name="username" value="root"></property>
                <property name="password" value="123456"></property>
            </dataSource>
        </environment>
    </environments>
    <!-- 指定映射配置文件的位置，映射配置文件指的是每个mapper独立的配置文件
     如果是用注解来配置的话，此处应该使用class属性指定被注解的mapper全限定类名-->
    <mappers>
        <mapper class="com.cong.mapper.AccountMapper"></mapper>
    </mappers>
</configuration>

5.创建测试类

import com.cong.mapper.AccountMapper;
import com.cong.pojo.Account;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.InputStream;
import java.util.List;

public class Test {
    public static void main(String[] args) throws Exception {
        //1.读取配置文件
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.创建SqlSessionFactory工厂
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        //3.使用工厂生产SqlSession对象
        SqlSession session = factory.openSession();
        //4.使用SqlSession创建Dao接口的代理对象
        AccountMapper accountMapper = session.getMapper(AccountMapper.class);
        //5.使用代理对象执行方法
        List<Account> accounts = accountMapper.findAll();
        for(Account account : accounts){
            System.out.println(account);
        }
        System.out.println("--------------------------------------");
        Account account = accountMapper.findById(1);
        System.out.println(account.toString());
        //6.释放资源
        session.close();
        in.close();
    }
}