Mybatis具体的使用 - 《猿人养成记》

导入架包,提取码(8toe)

构建mybatis-config.xml核心配置文件，例如

<?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>
  <!-- 加载数据库配置信息 -->
  <properties resource="database.properties"></properties>
  <!-- 设置日志行为 -->
  <settings>
      <setting name="logImpl" value="LOG4J"></setting>
  </settings>
  <!-- 设置类型别名 -->
  <typeAliases>
            <!-- <typeAlias alias="User" type="com.apeman1024.mybatis.User"/>-->
            <package name="com.apeman1024.mybatis"/>
  </typeAliases>
  <!-- 配置运行环境 -->
  <environments default="dev">
      <!-- 不同的运行环境 -->
      <environment id="dev">
          <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>
      <environment id="test">
          <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>
      <environment id="pro">
          <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="com/apeman1024/dao/UserMapper.xml"/>
  </mappers>
</configuration>

配置log4j.properties文件

log4j.rootLogger =debug,stdout,logfile
log4j.appender.stdout = org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout = org.apache.log4j.SimpleLayout
log4j.appender.logfile = org.apache.log4j.FileAppender
log4j.appender.logfile.layout = org.apache.log4j.PatternLayout
log4j.appender.fileAppender.layout.ConversionPattern = %d{yyyy-MM-dd HH:mm:ss}
log4j.logger.com.ibatis=DEBUG
log4j.logger.com.ibatis.common.jdbc.SimpleDataSource=DEBUG
log4j.logger.com.ibatis.common.jdbc.ScriptRunner=DEBUG
log4j.logger.com.ibatis.sqlmap.engine.impl.SqlMapClientDelegate=DEBUG
log4j.logger.java.sql.Connection=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG

配置database.properties文件

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/qidi?useUnicode=true&amp;characterEncoding=utf8
username=root
password=root

编写相应的映射文件UserMapper.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="com.apeman1024.dao.UserMapper">
  <select id="count" resultType="int">
      select count(1) from user
  </select>
<!--      <select id="userlist" resultType="com.apeman1024.mybatis.User">
      select * from user
  </select>-->
  <select id="userlist" resultType="User">
      select * from user
  </select>
  <select id="getUser" resultType="User">
      select * from user
  </select>
</mapper>

搭建工具类 ``` 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;

public class Util { private static SqlSessionFactory sqlSessionFactory ; static { String path=”mybatis-config.xml”; InputStream inputStream; try { inputStream = Resources.getResourceAsStream(path); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); } catch (IOException e) { e.printStackTrace(); }

}
public static SqlSession getSession() {
    return sqlSessionFactory.openSession();
}

}


- 
sqlSession使用的两种方式

@Test
public void test01() {
    //mysql读取数据库的第一种方法
    SqlSession session = Util.getSession();
    int selectOne = session.selectOne("com.apeman1024.dao.UserMapper.count");
    System.out.println(selectOne);
}
@Test
public void test02() {
    //mysql读取数据库的第二种方式,需要构建接口类，推荐使用
    SqlSession session = Util.getSession();
    Integer count = session.getMapper(UserMapper.class).getCount();
    System.out.println(count);
}


- 
mybatis中的属性resultType和resultMap的区别：[区别](https://www.jianshu.com/p/df86cb39d672)
- 
mybatis中的insert和update以及delete默认不自动提交
- 
mybatis中当属性列允许为空时最好指定一下属性列的jdbsType类型：[类型映射](https://blog.csdn.net/bisal/article/details/82775403)
- 
mybatis在传递多个参数时： 在多个参数的情况下，默认它们将会以 param 加上它们在参数列表中的位置来命名，比如：#{param1}、#{param2}等。如果你想（在有多个参数时）自定义参数的名称，那么你可以在参数上使用 @Param("paramName") 注解。
- 
mybatis分页查询的方法：为映射方法添加RowBounds实例，其中在RowBounds构造方法中的参数offset：在结果集的第offset个元素开始取，limit指：取多少个元素
```java
List<User3> getUs1(@Param("mm") Object m,RowBounds  ro);//映射方法
//
RowBounds ro=new RowBounds(1,2);
List<User3> us1 = session.getMapper(IdMapper.class).getUs1("111",ro);