MyBatis学习
什么是MyBatis
MyBatis是一款一流的支持自定义SQL、存储过程和高级映射的持久化框架。MyBatis几乎消除了所有的JDBC代码，也基本不需要手工去设置参数和获取检索结果。MyBatis能够使用简单的XML格式或者注解进行来配置，能够映射基本数据元素、Map接口和POJOs（普通java对象）到数据库中的记录。
入门
所有的MyBatis应用都以SqlSessionFactory实例为中心。SqlSessionFactory实例通过 SqlSessionFactoryBuilder来获得，SqlSessionFactoryBuilder能够从XML配置文件或者通过自定义编写的配置类（Configurationclass），来创建一个SqlSessionFactory实例。
项目结构如下：
SQL
CREATE TABLE user ( id int(11) NOT NULL AUTO_INCREMENT, username varchar(20) NOT NULL, password varchar(20) NOT NULL, PRIMARY KEY (id) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Config.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">
<configuration>
<properties resource="jdbc.properties"/>
<environments default="development">
<environment id="development">
<transactionManager type="jdbc"/>
<dataSource type="pooled">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="entity/mapper.xml"/>
</mappers>
</configuration>
jdbc.properties
driver=com.mysql.jdbc.Driver url=jdbc:mysql://localhost:3306/test username=root password=root
mapper.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="entity.mapper">
<insert id="insertUser" parameterType="entity.User">
insert into user(username,password) values(#{username},#{password})
</insert>
<select id="selectUser" parameterType="int" resultType="entity.User">
select * from user where id=#{id}
</select>
</mapper>
User.java
package entity;
import java.io.Serializable;
@SuppressWarnings("serial")
public class User implements Serializable {
private int id;
private String username;
private String password;
public User() {
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public User(String name, String pwd) {
this.username = name;
this.password = pwd;
}
public User(int id, String username, String password) {
this.id = id;
this.username = username;
this.password = password;
}
public String toString() {
return "User [id = " + id + " , username = " + username + ", password = " + password + "]";
}
}
MyBatisTest.java
package test;
import java.io.IOException;
import java.io.InputStream;
import entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
public class MyBatisTest {
public static void main(String[] args) {
try {
/*获取config文件*/
InputStream inputStream = Resources.getResourceAsStream("Config.xml");
/*通过SqlSessionFactoryBuilder获得配置文件流来创建SqlSessionFactory实例*/
SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
/*创建能执行映射文件中sql的sqlSession实例*/
SqlSession session = sessionFactory.openSession(true);
User user = new User("xxt", "1");
/*映射sql的标识字符串*/
String statement = "entity.mapper" + ".insertUser";
int i = session.insert(statement, user);
if (i == 1)
System.out.println("新增加用户成功！！！！");
else
System.out.println("添加用户失败！！！");
} catch (IOException e) {
e.printStackTrace();
}
}
}
运行结果：
第二种方法：半annotation不需要mapper.xml再加一个Dao接口UserMapper
package entity;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
public interface UserMapper {
@Insert("insert into user(name, age) values(#{name}, #{age})")
public int insertUser(User user);
@Select("select * from user where id=#{id}")
public User selectUser(int id);
}
Config.xml改为（注意，是mappers改动了）
<?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">
<configuration>
<properties resource="jdbc.properties"/>
<environments default="development">
<environment id="development">
<transactionManager type="jdbc"/>
<dataSource type="pooled">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>
<mappers>
<!-- <mapper resource="entity/mapper.xml"/> -->
<mapper class="entity.UserMapper"/>
</mappers>
</configuration>
加一个测试类
package test;
import java.io.IOException;
import java.io.InputStream;
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 entity.User;
import entity.UserMapper;
public class UserMapperTest {
public static void main(String[] args) {
try {
/* 获取config文件 */
InputStream inputStream = Resources.getResourceAsStream("Config.xml");
/* 通过SqlSessionFactoryBuilder获得配置文件流来创建SqlSessionFactory实例 */
SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
/* 创建能执行映射文件中sql的sqlSession实例 */
SqlSession session = sessionFactory.openSession(true);
UserMapper userMapper = session.getMapper(UserMapper.class);
User user = userMapper.selectUser(1);
System.out.println(user.getUsername());
session.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
结果
从XML中创造SqlSessionFactory
从XML文件中创造SqlSessionFactory实例是非常简单的。推荐使用一个类路径资源来进行配置，你也可以使用一个Reader实例，甚至使用URL路径。
MyBatis有一个Resources通用类，类中有许多方法可以简单地从类路径和其他地址中加载资源。
Stringresource="org/mybatis/example/Configuration.xml"; Readerreader=Resources.getResourceAsReader(resource); sqlMapper=newSqlSessionFactoryBuilder().build(reader);
ML文件包含了许多MyBatis的核心设置，包括一个获取数据库连接（Connection）实例的数据源（DataSource），和一个决定事务作用域和操作的TransactionManager。全部的XML配置文件的内容将在以后提到，先给出一个简单的样子。
<?xmlversion="1.0"encoding="UTF-8"?>
<!DOCTYPEconfiguration
PUBLIC"-//mybatis.org//DTDConfig3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<environmentsdefault = development ">
<environment id = development ">
<transactionManagertype = JDBC " />
<dataSourcetype = POOLED ">
<propertyname = driver " value="${driver}" />
<propertyname = url " value="${url}" />
<propertyname = username " value="${username}" />
<propertyname = password " value="${password}" />
</dataSource>
</environment>
</environments>
<mappers>
<mapperresource = org / mybatis / example /
BlogMapper.xml " />
</mappers>
</configuration>
XML配置文件中还有其它许多内容，上面的例子只是指出了最重要的部分。注意这个XML的标头，需要一个DTD验证文档。environment项里包含了事务管理和连接池的环境配置。mappers项中包含了一系列SQL语句映射定义的XML文件。
不使用XML文件新建SqlSessionFactory
什么是MyBatis
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什么是MyBatis
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什么是MyBatis
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什么是MyBatis
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什么是MyBatis
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什么是MyBatis
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什么是MyBatis
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什么是MyBatis
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什么是MyBatis
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什么是MyBatis
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什么是MyBatis
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什么是MyBatis
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什么是MyBatis
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什么是MyBatis
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