1.分步查询

接口1中的代码如下：

public interface DepartmentMapper {public Department getDeptById(Integer id);
}

1.对应的sql中的文件如下

<?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.atguigu.mybatis.dao.DepartmentMapper"><select id="getDeptById" resultType="com.atguigu.mybatis.bean.Department">select id,dept_name departmenName from tb1_dept where id=#{id}</select>
</mapper>

接口2中的代码如下：

public interface EmployeeMapperPlus {public Employee getEmpByIdStep(Integer id);
}

接口2对应的sql代码如下

 <resultMap type="com.atguigu.mybatis.bean.Employee" id="MyEmpByStep"><id column="id" property="id"/><result column="last_name" property="lastName"/><result column="email" property="email"/><result column="gender" property="gender"/><association property="dept" select="com.atguigu.mybatis.dao.DepartmentMapper.getDeptById"column="d_id"></association></resultMap><select id="getEmpByIdStep" resultMap="MyEmpByStep">select * from tb1_employee where id=#{id}</select>

2.查询的延迟加载

在配置文件中配置如下两个配置

 <settings><!--<setting name="mapUnderscoreToCamelCase" value="true"/>--><!-- 显示的指定每个我们需要更改的配置的值，即使他是默认的，防止版本更新带来的问题 --><setting name="lazyLoadingEnabled" value="true"/><setting name="aggressiveLazyLoading" value="false"/></settings>

测试运行结果如下：

DEBUG 07-03 09:40:50,571 ==>  Preparing: select * from tb1_employee where id=?   (BaseJdbcLogger.java:145) 
DEBUG 07-03 09:40:50,597 ==> Parameters: 1(Integer)  (BaseJdbcLogger.java:145) 
DEBUG 07-03 09:40:50,657 <==      Total: 1  (BaseJdbcLogger.java:145) 
jerry

3.查询部门的时候将部门对应的所有的员工信息也查询出来

类代码如下

public class Department {private Integer id;//省略get和set方法private String departmenName;private List<Employee> emps;}

接口代码如下：

public interface DepartmentMapper {public Department getDeptById(Integer id);public Department getDeptByIdPlus(Integer id);
}

sql配置文件如下：

<resultMap type="com.atguigu.mybatis.bean.Department" id="MyDept"><id column="d_id" property="id"/><result column="dept_name" property="departmenName"/><collection property="emps" ofType="com.atguigu.mybatis.bean.Employee"><id column="id" property="id"/><result column="last_name" property="lastName"/><result column="email" property="email"/><result column="gender" property="gender"/></collection></resultMap><select id="getDeptByIdPlus" resultMap="MyDept">SELECT e.*,d.dept_namefrom tb1_dept dLEFT JOIN tb1_employee eon d.id=e.d_idwhere d.id=#{id}</select>

测试代码如下：

 @Testpublic void test04() throws Exception{String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);SqlSession openSession=sqlSessionFactory.openSession();  DepartmentMapper mapper=openSession.getMapper(DepartmentMapper.class);Department department=mapper.getDeptByIdPlus(1);System.out.println(department);List<Employee> emps=department.getEmps();for(Employee emp:emps) {System.out.println(emp);}}

4.定义使用分布查询完成

接口1中的代码如下：

public interface EmployeeMapperPlus {public Employee getEmpById(Integer id);public Employee getEmpAndDept(Integer id);public Employee getEmpByIdStep(Integer id);public List<Employee> getEmpsByDeptId(Integer deptId);
}

涉及到的sql查询语句如下

 <select id="getEmpsByDeptId" resultType="com.atguigu.mybatis.bean.Employee">select * from tb1_employee where d_id=#{deptId}</select>

接口2中的代码如下：

public interface DepartmentMapper {public Department getDeptById(Integer id);public Department getDeptByIdPlus(Integer id);public Department getDeptByIdStep(Integer id);
}

涉及到的sql查询语句如下

 <resultMap type="com.atguigu.mybatis.bean.Department" id="MyDeptStep"><id column="id" property="id"/><result column="dept_name" property="departmenName"/><collection property="emps" select="com.atguigu.mybatis.dao.EmployeeMapperPlus.getEmpsByDeptId"column="id"><!--多列的值传递过去column="{key1=column1,key2=column2}"fecthType="lazy"lazy：延迟加载eager：立即加载--></collection></resultMap><select id="getDeptByIdStep" resultMap="MyDeptStep">select id,dept_name departmenName from tb1_dept whereid=#{id}</select>

5.需求：封装Employee

如果查出的是女生，就把部门信息查询出来，否则不查询；
如果是男生，就把last_name这一列的值赋值为email
sql查詢配置如下

 <resultMap type="com.atguigu.mybatis.bean.Employee" id="MyEmpDis"><id column="id" property="id"></id><result column="last_name" property="lastName"></result><result column="email" property="email"></result><result column="gender" property="gender"></result><discriminator javaType="string" column="gender"><case value="0" resultType="com.atguigu.mybatis.bean.Employee"><association property="dept" select="com.atguigu.mybatis.dao.DepartmentMapper.getDeptById"column="d_id"></association></case><case value="1" resultType="com.atguigu.mybatis.bean.Employee"><id column="id" property="id"></id><result column="last_name" property="lastName"></result><result column="last_name" property="email"></result><result column="gender" property="gender"></result></case></discriminator></resultMap><select id="getEmpByIdStep" resultMap="MyEmpDis">select * from tb1_employee where id=#{id}</select>
com.atguigu.mybatis.dao.DepartmentMapper.getDeptById的配置如下<select id="getDeptByIdStep" resultMap="MyDeptStep">select id,dept_name departmenName from tb1_dept whereid=#{id}</select>

測試代碼如下：

 @Testpublic void test04() throws Exception{String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);SqlSession openSession=sqlSessionFactory.openSession();  EmployeeMapperPlus mapper=openSession.getMapper(EmployeeMapperPlus.class);Employee employee=mapper.getEmpByIdStep(1);System.out.println(employee);}

6.动态sql

1.if标签

7.OGNL

1.if标签测试

public interface EmployeeMapperDynamicSQL {public List<Employee> getEmpsByConditionIf(Employee employee);
}

sql配置文件

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.atguigu.mybatis.dao.EmployeeMapperDynamicSQL"><select id="getEmpsByConditionIf" resultType="com.atguigu.mybatis.bean.Employee" >select id,last_name lastName,email,gender from tb1_employee<where> <!--只会去掉第一个多出来的and或者or--><if test="id!=null">id=#{id}</if><if test="lastName!=null and lastName!=&quot;&quot;">and last_name like #{lastName}</if><if test="email!=null and email.trim()!=&quot;&quot;">and email=#{email}</if><if test="gender==0 or gender==1">and gender=#{gender}</if></where></select>
</mapper>

8.使用trim进行查询

<select id="getEmpsByConditionTrim" resultType="com.atguigu.mybatis.bean.Employee">select id,last_name lastName,email,gender from tb1_employee<!-- prefix:前缀，给拼串后的整个字符串加一个前缀prefixOverrides：去掉整个字符串前面多余的字符suffix:给拼串后的整个字符串加一个后缀suffixOverrides:去掉整个字符串后面多余的字符--><trim prefix="where" prefixOverrides="" suffix="" suffixOverrides="and"> <if test="id!=null">id=#{id} and</if><if test="lastName!=null and lastName!=&quot;&quot;">last_name like #{lastName} and</if><if test="email!=null and email.trim()!=&quot;&quot;">email=#{email} and</if><if test="gender==0 or gender==1">gender=#{gender}</if></trim> 
</select>

9.choose标签

<select id="getEmpsByConditionChoose" resultType="com.atguigu.mybatis.bean.Employee">select id,last_name lastName,email,gender from tb1_employee<where><choose ><when test="id!=null">id=#{id}</when><when test="lastName!=null">last_name like #{lastName}</when><when test="email!=null">email=#{email}</when><otherwise>gender=0</otherwise></choose></where></select>

10.set标签

 <select id="updateEmp">update tb1_employee<set><if test="lastName!=null">last_name=#{lastName},</if><if test="email!=null">email=#{email},</if><if test="gender!=null">gender=#{gender},</if></set> <where>id=#{id}</where></select>

测试代码

 @Testpublic void test05() throws Exception{String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);SqlSession openSession=sqlSessionFactory.openSession();  EmployeeMapperDynamicSQL mapper=openSession.getMapper(EmployeeMapperDynamicSQL.class);Employee employee=new Employee(3,"%e%","test1","0");mapper.updateEmp(employee);openSession.commit();openSession.close();}

测试结果为：

DEBUG 07-03 15:40:05,351 ==>  Preparing: update tb1_employee SET last_name=?, email=?, gender=? WHERE id=?   (BaseJdbcLogger.java:145) 
DEBUG 07-03 15:40:05,386 ==> Parameters: %e%(String), test1(String), 0(String), 3(Integer)  (BaseJdbcLogger.java:145) 

11.foreach标签的使用(批量查询)

接口中申明的函数

public List<Employee> getEmpsByConditionForeach(@Param("ids") List<Integer> ids);

sql中写的语句

 <select id="getEmpsByConditionForeach" resultType="com.atguigu.mybatis.bean.Employee">select * from tb1_employee where id in<!-- collection：指定要遍历的集合list类型的参数会特殊处理封装在map中，map的key就叫listitem：将当前遍历出的元素赋值给指定的变量index:索引。遍历list的时候是index的索引。遍历map的时候index表示的就是map的key,item就是map的值--><foreach collection="ids" item="item_id" separator="," open="(" close=")">#{item_id}</foreach></select>

java测试代码如下

 @Testpublic void test05() throws Exception{String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);SqlSession openSession=sqlSessionFactory.openSession();  EmployeeMapperDynamicSQL mapper=openSession.getMapper(EmployeeMapperDynamicSQL.class);List<Employee> employees=mapper.getEmpsByConditionForeach(Arrays.asList(1,2,3));for(Employee employee:employees) {System.out.println(employee);}openSession.close();}

运行结果如下：

DEBUG 07-03 19:51:47,535 ==>  Preparing: select * from tb1_employee where id in ( ? , ? , ? )   (BaseJdbcLogger.java:145) 
DEBUG 07-03 19:51:47,582 ==> Parameters: 1(Integer), 2(Integer), 3(Integer)  (BaseJdbcLogger.java:145) 
DEBUG 07-03 19:51:47,700 <==      Total: 2  (BaseJdbcLogger.java:145) 
Employee [id=1, lastName=jerry, email=jerry@atguigu.com, gender=0, dept=null]
Employee [id=3, lastName=%e%, email=test1, gender=0, dept=null]

12.foreach标签的使用(批量保存)

接口代码如下：

 public void addEmps(@Param("emps")List<Employee> emps);

sql配置文件如下：

 <insert id="addEmps">insert into tb1_employee(last_name,email,gender,d_id)values<foreach collection="emps" item="emp" separator=",">(#{emp.lastName},#{emp.email},#{emp.gender},#{emp.dept.id})</foreach></insert>

测试代码如下：

@Test
public void test05() throws Exception{String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);SqlSession openSession=sqlSessionFactory.openSession();  EmployeeMapperDynamicSQL mapper=openSession.getMapper(EmployeeMapperDynamicSQL.class);List<Employee> emps=new ArrayList<>();Department dept=new Department(1);emps.add(new Employee(null,"smith","smith","1",dept));emps.add(new Employee(null,"smith2","smith","1",dept));emps.add(new Employee(null,"smith3","smith","0",dept));emps.add(new Employee(null,"smith4","smith","0",dept));mapper.addEmps(emps);openSession.commit();openSession.close();
}

第二种方式
数据库连接配置文件中做如下的配置

 jdbc.url:jdbc:mysql://localhost:3306/mybaties?serverTimezone=GMT&&allowMultiQueries=TRUE

sql语句如下：

<insert id="addEmps"><foreach collection="emps" item="emp" separator=";">insert into tb1_employee(last_name,email,gender,d_id)values(#{emp.lastName},#{emp.email},#{emp.gender},#{emp.dept.id})</foreach>
</insert>

13.Oracle数据库批量保存

实现代码：

14.mybatis中两个重要的内置参数

两个内置参数：
不只是方法传递过来的参数可以用来被判断取值
mybaties默认还有两个内置参数：
1._parameter:代表整个参数
单个参数：_parameter就是这个参数
多个参数：参数会被封装为一个map：_parameter就是代表这个map
2._databaseId:如果配置了databaseIdProvider标签
_databaseId就是代表当前数据库的别名oracle
测试接口函数如下：

public List<Employee> getEmpsTestInnerParameter(Employee employee);

sql语句如下：

 <select id="getEmpsTestInnerParameter" resultType="com.atguigu.mybatis.bean.Employee"><if test="_databaseId=='mysql'">select * from tb1_employee<if test="_parameter!=null">where last_name=#{_parameter.lastName}</if></if><if test="_databaseId=='oracle'">select * from employees</if></select>

15.绑定变量

 <select id="getEmpsTestInnerParameter" resultType="com.atguigu.mybatis.bean.Employee"><bind name="_lastName" value="'%'+lastName+'%'"/><if test="_databaseId=='mysql'">select * from tb1_employee<if test="_parameter!=null">where last_name like #{_lastName}</if></if><if test="_databaseId=='oracle'">select * from employees</if></select>

16.sql标签

抽取可重用的sql标签

<sql id="column">id,last_name lastName,email,gender,${testColumn}
</sql>

引用的sql语句如下：

 <select id="getEmpsByConditionIf" resultType="com.atguigu.mybatis.bean.Employee" >select <include refid="column"><property name="testColumn" value="abc"></property></include> from tb1_employeewhere 1=1  <if test="id!=null">and id=#{id}</if><if test="lastName!=null and lastName!=&quot;&quot;">and last_name like #{lastName}</if><if test="email!=null and email.trim()!=&quot;&quot;">and email=#{email}</if><if test="gender==0 or gender==1">and gender=#{gender}</if></select>

作用：
1.sql抽取：经常将要查询的列名，或者插入用的列名抽取出来方便引用
2.include来引用已经抽取的sql语句
3.include还可以自定义一些property，sql标签内部就能使用自定义的属性
取值方式为${prop}，不能使用#{}

17.MyBatis的缓存机制

两级缓存
一级缓存：本地缓存，与数据库同一次会话查询到的数据会放在本地缓存中，以后如果需要获取相同的数据，直接从数据库中拿，没必要去查询数据库；属于sqlSession级别的缓存，一级缓存是一直开启的。
一级缓存失效的情况(没有使用到当前一级缓存的情况，需要再向数据库发出查询)
1.sqlSession不同。
2.sqlSession相同，查询条件不同。(当前一级缓存中还没有这个数据)。
3.sqlSession相同，两次查询之间执行了增删改操作(这次增删改可能对当前数据有影响)
4.sqlSession相同，手动清楚了一级缓存(缓存清空)
openSessison.clearCache();
测试样例
sql配置如下：

 <select id="getEmpById" resultType="employee" databaseId="mysql">select * from tb1_employee where id = #{id}</select>

测试代码如下：

 @Testpublic void test02() throws Exception{String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);SqlSession openSession=sqlSessionFactory.openSession();  try {EmployeeMapper mapper=openSession.getMapper(EmployeeMapper.class);Employee emp01=mapper.getEmpById(1);System.out.println(emp01);Employee emp02=mapper.getEmpById(1);System.out.println(emp02);System.out.println(emp01==emp02);}finally {openSession.close();}}

测试结果如下：

DEBUG 07-06 09:59:39,813 ==>  Preparing: select * from tb1_employee where id = ?   (BaseJdbcLogger.java:145) 
DEBUG 07-06 09:59:39,861 ==> Parameters: 1(Integer)  (BaseJdbcLogger.java:145) 
DEBUG 07-06 09:59:39,914 <==      Total: 1  (BaseJdbcLogger.java:145) 
Employee [id=1, lastName=jerry, email=jerry@atguigu.com, gender=0, dept=null]
Employee [id=1, lastName=jerry, email=jerry@atguigu.com, gender=0, dept=null]
true

二级缓存：全局缓存。基于namespace级别的缓存，一个namespace对应一个二级缓存。
工作机制：
1.一个会话，查询一条数据，这个数据就会被放在当前会话的一级缓存中；
2.如果会话关闭，一级缓存中的数据会被保存到二级缓存中，新的会话查询信息 ，就可以参照二级缓存中的内容；
3.不同的namespace查出的数据会放在自己对应的缓存中(map)。查出的数据都会被默认先放到一级缓存中，只有会话提交或者关闭以后，一级缓存中的数据才会转到二级缓存中。
测试样例：
在配置文件中进行配置

 <settings><setting name="chacheEnable" value="true"/></settings>

去mapper.xml中配置使用二级缓存

 <cache eviction="FIFO" flushInterval="60000" readOnly="false" size="1024" />

属性说明：
eviction=“FIFO”：缓存回收策略：
• LRU – 最近最少使用的：移除最长时间不被使用的对象。
• FIFO – 先进先出：按对象进入缓存的顺序来移除它们。
• SOFT – 软引用：移除基于垃圾回收器状态和软引用规则的对象。
• WEAK – 弱引用：更积极地移除基于垃圾收集器状态和弱引用规则的对象。
• 默认的是 LRU。
flushInterval：刷新多长时间清空一次
• 默认情况是不设置，也就是没有刷新间隔，缓存仅仅调用语句时刷新
size：引用数目，正整数
• 代表缓存最多可以存储多少个对象，太大容易导致内存溢出
readOnly：只读，true/false
• true：只读缓存；会给所有调用者返回缓存对象的相同实例。因此这些对象不能被修改。这提供了很重要的性能优势。
• false：读写缓存；会返回缓存对象的拷贝（通过序列化）。这会慢一些，但是安全，因此默认是 false。
type="";指定自定义缓存的全类名;实现Cache接口即可。
POJO需要实现序列化接口

public class Employee implements Serializable{private static final long serialVersionUID = 857579980893303333L;private Integer id;private String lastName;private String email;private String gender;private Department dept;//方法省略
}

public class Department implements Serializable{private static final long serialVersionUID = 8575799808933023456L;private Integer id;private String departmenName;private List<Employee> emps;
}//方法省略

测试方法如下：

 @Testpublic void test03() throws Exception{String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);SqlSession openSession=sqlSessionFactory.openSession();  SqlSession openSession2=sqlSessionFactory.openSession();  try {EmployeeMapper mapper=openSession.getMapper(EmployeeMapper.class);EmployeeMapper mapper2=openSession2.getMapper(EmployeeMapper.class);Employee emp01=mapper.getEmpById(1);System.out.println(emp01);openSession.close();Employee emp02=mapper2.getEmpById(1);System.out.println(emp02);openSession2.close();}finally {openSession.close();}}

运行结果如下：

DEBUG 07-06 12:12:40,674 Cache Hit Ratio [com.atguigu.mybatis.dao.EmployeeMapper]: 0.0  (LoggingCache.java:62) 
DEBUG 07-06 12:12:40,685 ==>  Preparing: select * from tb1_employee where id = ?   (BaseJdbcLogger.java:145) 
DEBUG 07-06 12:12:40,730 ==> Parameters: 1(Integer)  (BaseJdbcLogger.java:145) 
DEBUG 07-06 12:12:40,786 <==      Total: 1  (BaseJdbcLogger.java:145) 
Employee [id=1, lastName=jerry, email=jerry@atguigu.com, gender=0, dept=null]
DEBUG 07-06 12:12:40,838 Cache Hit Ratio [com.atguigu.mybatis.dao.EmployeeMapper]: 0.5  (LoggingCache.java:62) 
Employee [id=1, lastName=jerry, email=jerry@atguigu.com, gender=0, dept=null]

18.和缓存有关的设置/属性：

1)cacheEbabled=true：false;关闭缓存(关闭二级缓存，一级缓存一直可用的)
2)每个select标签都有useCash=“true”
false:不使用缓存(一级缓存依然使用，二级缓存不使用)
3)每个增删改标签的：flushCash=“true”
增删改执行完成后就会清楚缓存
测试：flushCache=“true”,一级和二级缓存就清空了。
4)sqlSession.clearCache();只是清除当前session的一级缓存。
5)localCacheScope:本地缓存作用域(一级缓存session)；当前会话的所有数据保存在会话缓存中。
statement可以禁用一级缓存。

19.缓存工作原理示意图

20.第三方缓存整合

1)导入第三方缓存包即可；
2)导入与第三方缓存整合的适配包
3)mapper.xml中使用自定义缓存

21.第三方整合结构图

22.MyBatis Generator逆向工程

1.导入逆向包
2.配置文件
大的主目录下配置文件mbg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfigurationPUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN""http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<generatorConfiguration><!-- targetRuntime="MyBatis3Simple":生成简单版的CRUDMyBatis3:豪华版--><context id="DB2Tables" targetRuntime="MyBatis3Simple"><!-- jdbcConnection：指定如何连接到目标数据库 --><jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"connectionURL="jdbc:mysql://localhost:3306/mybaties?serverTimezone=GMT"userId="root"password="stoneSml@123"></jdbcConnection><javaTypeResolver ><property name="forceBigDecimals" value="false" /></javaTypeResolver><!-- javaModelGenerator：指定javaBean的生成策略 targetPackage="test.model"：目标包名targetProject="\MBGTestProject\src"：目标工程--><javaModelGenerator targetPackage="com.atguigu.mybatis.bean" targetProject=".\src"><property name="enableSubPackages" value="true" /><property name="trimStrings" value="true" /></javaModelGenerator><!-- sqlMapGenerator：sql映射生成策略： --><sqlMapGenerator targetPackage="com.atguigu.mybatis.dao"  targetProject=".\conf"><property name="enableSubPackages" value="true" /></sqlMapGenerator><!-- javaClientGenerator:指定mapper接口所在的位置 --><javaClientGenerator type="XMLMAPPER" targetPackage="com.atguigu.mybatis.dao"  targetProject=".\src"><property name="enableSubPackages" value="true" /></javaClientGenerator><!-- 指定要逆向分析哪些表：根据表要创建javaBean --><table tableName="tb1_dept" domainObjectName="Department"></table><table tableName="tb1_employee" domainObjectName="Employee"></table></context>
</generatorConfiguration>

23.逆向工程使用MyBatis3的测试结果

@Testpublic void testMyBatis3() throws IOException{SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();SqlSession openSession = sqlSessionFactory.openSession();try{EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);//xxxExample就是封装查询条件的//1、查询所有//List<Employee> emps = mapper.selectByExample(null);//2、查询员工名字中有e字母的，和员工性别是1的//封装员工查询条件的exampleEmployeeExample example = new EmployeeExample();//创建一个Criteria，这个Criteria就是拼装查询条件//select id, last_name, email, gender, d_id from tbl_employee //WHERE ( last_name like ? and gender = ? ) or email like "%e%"Criteria criteria = example.createCriteria();criteria.andLastNameLike("%e%");criteria.andGenderEqualTo("1");Criteria criteria2 = example.createCriteria();criteria2.andEmailLike("%e%");example.or(criteria2);List<Employee> list = mapper.selectByExample(example);for (Employee employee : list) {System.out.println(employee.getId());}
}finally{openSession.close();}}   

24. MyBatis工作原理

1.

25.

默认情况下，MyBatis 允许使用插件来拦截的方法调用包括：
• Executor (update, query, flushStatements, commit, rollback,
getTransaction, close, isClosed)
• ParameterHandler (getParameterObject, setParameters)
• ResultSetHandler (handleResultSets, handleOutputParameters)
• StatementHandler (prepare, parameterize, batch, update, query)


2.

3

4.

25.默认情况下，MyBatis 允许使用插件来拦截的方法调用包括：

• Executor (update, query, flushStatements, commit, rollback,
getTransaction, close, isClosed)
• ParameterHandler (getParameterObject, setParameters)
• ResultSetHandler (handleResultSets, handleOutputParameters)
• StatementHandler (prepare, parameterize, batch, update, query)