mybatis 注解方式，增，删，改，全查,单查，模糊，总数，CRUD操作

1.搭建maven ，导入相关jar依赖

<!--打包成jar包-->
    <packaging>jar</packaging>
    <!--所有相关jar包依赖和下载的区域-->
    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <!--日志包-->
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
        <dependency>
            <!--单元测试包-->
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>
    </dependencies>

2.导入log4j的固定日志文件，具体参照，https://mp.csdn.net/mdeditor/95371441# 文档中有这个知识点。
配置连接数据库信息的mybatis 主配置文件 名：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>
    <!--配置实体类路径的别名-->
    <typeAliases>
        <package name="entity"></package>
    </typeAliases>
    <!-- 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 name="url" value="jdbc:mysql://localhost:3306/test"/>
                <property name="username" value="root"/>
                <property name="password" value="123"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 指定映射配置中所有接口的位置 -->
    <mappers>
        <package name="dao"></package>
    </mappers>
</configuration>

3.创建实体类包和类。并实现序列化接口。
4.写接口类里面的方法，和注解，和sql 指令

public interface IStudentDao {
   //查询所有学生
    @Select("select * from student")
    List<Student> query();
    // 新增学生
    @Insert( "insert into student (id,name,age,sex) " +
            " values(#{id},#{name},#{age},#{sex});")
    void add(Student student);
    //修改
    @Update("update student set name = #{name},age = #{age},sex = #{sex} where id = #{id};")
    void update(Student student);
    //删除
    @Delete("delete from student where id = #{id};")
    void delete(int id);
    //单查学生
    @Select("select * from student  where id = #{id}")
    Student findbyid(int id);
    //名字模糊查询
            //1.模糊条件需要，在前台，组装为 《'%经%'》 格式
        @Select("select * from student  where name like(#{name});")
            //2.模糊条件前台传入值为value,后台语句，定义好的格式，直接引用值
    //  @Select("select * from student  where name like '%${value}%'  ")
    List<Student> *(String name);
    //查询学生数量
    @Select("select count(*) from student")
    int count();
}

5.生成相应的测试方法。
day02,补充
1.表间关系，一对一的操作。

@Select("select * from Account")
    @Results(id = "accountMap" ,  value = {
        @Result(id = true,property = "id" , column = "id"),
        @Result(property = "money" , column = "money"),
        @Result(property = "stuId" , column = "stuId"),
        @Result(property = "student" ,column = "stuId",
                one = @One(select = "dao.IStudentDao.findbyid",
                        fetchType = FetchType.EAGER))
    })
    List<Account> query();

2.表间关系，一对多的操作。

//查询所有学生
    @Select("select * from student")
    @Results(id = "studentMap", value = {
        @Result(id = true , property = "id" ,column = "id"),
        @Result( property = "name" ,column = "name"),
        @Result( property = "age" ,column = "age"),
        @Result( property = "sex" ,column = "sex"),
        @Result( property = "accounts" ,column = "id",
                many = @Many(select = "dao.IAccountDao.findbyid",
                        fetchType = FetchType.LAZY))
    })
    List<Student> query();

3.配置二级缓存

先去主配置文件中，把cacheEnabled ,的值设为true ,开启二级缓存

再把接口类的二级缓存，设置为打开，默认是关闭的
    @CacheNamespace(blocking = true)