插件原理
插件原理
在四大对象创建的时候
1、每个创建出来的对象不是直接返回的，而是
interceptorChain.pluginAll(parameterHandler);
2、获取到所有的Interceptor（拦截器）（插件需要实现的接口）；
调用interceptor.plugin(target);返回target包装后的对象
3、插件机制，我们可以使用插件为目标对象创建一个代理对象；AOP（面向切面）
我们的插件可以为四大对象创建出代理对象；
代理对象就可以拦截到四大对象的每一个执行；
public Object pluginAll(Object target) {
for (Interceptor interceptor : interceptors) {
target = interceptor.plugin(target);
}
return target;
}
* 插件编写：
* 1、编写Interceptor的实现类
* 2、使用@Intercepts注解完成插件签名
* 3、将写好的插件注册到全局配置文件中
自定义插件
- 实现类
package com.atguigu.mybatis.dao;
import java.util.Properties;
import org.apache.ibatis.executor.parameter.ParameterHandler;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;
/**
* 完成插件签名：
* 告诉MyBatis当前插件用来拦截哪个对象的哪个方法
*/
@Intercepts(
{
@Signature(type=StatementHandler.class,method="parameterize",args=java.sql.Statement.class)
})
public class MyFirstPlugin implements Interceptor{
/**
* intercept：拦截：
* 拦截目标对象的目标方法的执行；
*/
@Override
public Object intercept(Invocation invocation) throws Throwable {
// TODO Auto-generated method stub
System.out.println("MyFirstPlugin...intercept:"+invocation.getMethod());
//动态的改变一下sql运行的参数：以前1号员工，实际从数据库查询3号员工
Object target = invocation.getTarget();
System.out.println("当前拦截到的对象："+target);
//拿到：StatementHandler==>ParameterHandler===>parameterObject
//拿到target的元数据
MetaObject metaObject = SystemMetaObject.forObject(target);
Object value = metaObject.getValue("parameterHandler.parameterObject");
System.out.println("sql语句用的参数是："+value);
//修改完sql语句要用的参数
metaObject.setValue("parameterHandler.parameterObject", 11);
//执行目标方法
Object proceed = invocation.proceed();
//返回执行后的返回值
return proceed;
}
/**
* plugin：
* 包装目标对象的：包装：为目标对象创建一个代理对象
*/
@Override
public Object plugin(Object target) {
// TODO Auto-generated method stub
//我们可以借助Plugin的wrap方法来使用当前Interceptor包装我们目标对象
System.out.println("MyFirstPlugin...plugin:mybatis将要包装的对象"+target);
Object wrap = Plugin.wrap(target, this);
//返回为当前target创建的动态代理
return wrap;
}
/**
* setProperties：
* 将插件注册时 的property属性设置进来
*/
@Override
public void setProperties(Properties properties) {
// TODO Auto-generated method stub
System.out.println("插件配置的信息："+properties);
}
}
- 注册插件
<!--plugins：注册插件 -->
<plugins>
<plugin interceptor="com.atguigu.mybatis.dao.MyFirstPlugin">
<property name="username" value="root"/>
<property name="password" value="123456"/>
</plugin>
<!--第二个插件-->
<plugin interceptor="com.atguigu.mybatis.dao.MySecondPlugin"></plugin>
</plugins>
pageHelper
配置文件
<plugins>
<plugin interceptor="com.github.pagehelper.PageInterceptor"></plugin>
</plugins>
测试
@Test
public void test01() throws IOException {
// 1、获取sqlSessionFactory对象
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
// 2、获取sqlSession对象
SqlSession openSession = sqlSessionFactory.openSession();
try {
EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
Page<Object> page = PageHelper.startPage(5, 1);
List<Employee> emps = mapper.getEmps();
//传入要连续显示多少页
PageInfo<Employee> info = new PageInfo<>(emps, 5);
for (Employee employee : emps) {
System.out.println(employee);
}
/*System.out.println("当前页码："+page.getPageNum());
System.out.println("总记录数："+page.getTotal());
System.out.println("每页的记录数："+page.getPageSize());
System.out.println("总页码："+page.getPages());*/
///xxx
System.out.println("当前页码："+info.getPageNum());
System.out.println("总记录数："+info.getTotal());
System.out.println("每页的记录数："+info.getPageSize());
System.out.println("总页码："+info.getPages());
System.out.println("是否第一页："+info.isIsFirstPage());
System.out.println("连续显示的页码：");
int[] nums = info.getNavigatepageNums();
for (int i = 0; i < nums.length; i++) {
System.out.println(nums[i]);
}
//xxxx
} finally {
openSession.close();
}
}
批量存储
- applicationContext.xml
<!--配置一个可以进行批量执行的sqlSession -->
<bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
<constructor-arg name="sqlSessionFactory" ref="sqlSessionFactoryBean"> </constructor-arg>
<constructor-arg name="executorType" value="BATCH"></constructor-arg>
</bean>
- service
package com.atguigu.mybatis.service;
import java.util.List;
import org.apache.ibatis.session.SqlSession;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.atguigu.mybatis.bean.Employee;
import com.atguigu.mybatis.dao.EmployeeMapper;
@Service
public class EmployeeService {
@Autowired
private EmployeeMapper employeeMapper;
@Autowired
private SqlSession sqlSession;
public List<Employee> getEmps(){
//执行mapp的方法进行批量操作即可
//EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
return employeeMapper.getEmps();
}
}
@Test
public void testBatch() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
//可以执行批量操作的sqlSession
SqlSession openSession = sqlSessionFactory.openSession(ExecutorType.BATCH);
long start = System.currentTimeMillis();
try{
EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
for (int i = 0; i < 10000; i++) {
mapper.addEmp(new Employee(UUID.randomUUID().toString().substring(0, 5), "b", "1"));
}
openSession.commit();
long end = System.currentTimeMillis();
//批量：（预编译sql一次==>设置参数===>10000次===>执行（1次））
//Parameters: 616c1(String), b(String), 1(String)==>4598
//非批量：（预编译sql=设置参数=执行）==》10000 10200
System.out.println("执行时长："+(end-start));
}finally{
openSession.close();
}
}
处理枚举类型
枚举类
package com.atguigu.mybatis.bean;
import com.sun.org.apache.bcel.internal.generic.RETURN;
/**
* 希望数据库保存的是100,200这些状态码，而不是默认0,1或者枚举的名
* @author lfy
*
*/
public enum EmpStatus {
LOGIN(100,"用户登录"),LOGOUT(200,"用户登出"),REMOVE(300,"用户不存在");
private Integer code;
private String msg;
private EmpStatus(Integer code,String msg){
this.code = code;
this.msg = msg;
}
public Integer getCode() {
return code;
}
public void setCode(Integer code) {
this.code = code;
}
public String getMsg() {
return msg;
}
public void setMsg(String msg) {
this.msg = msg;
}
//按照状态码返回枚举对象
public static EmpStatus getEmpStatusByCode(Integer code){
switch (code) {
case 100:
return LOGIN;
case 200:
return LOGOUT;
case 300:
return REMOVE;
default:
return LOGOUT;
}
}
}
类型处理器
package com.atguigu.mybatis.typehandler;
import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.TypeHandler;
import com.atguigu.mybatis.bean.EmpStatus;
/**
* 1、实现TypeHandler接口。或者继承BaseTypeHandler
* @author lfy
*
*/
public class MyEnumEmpStatusTypeHandler implements TypeHandler<EmpStatus> {
/**
* 定义当前数据如何保存到数据库中
*/
@Override
public void setParameter(PreparedStatement ps, int i, EmpStatus parameter,
JdbcType jdbcType) throws SQLException {
// TODO Auto-generated method stub
System.out.println("要保存的状态码："+parameter.getCode());
ps.setString(i, parameter.getCode().toString());
}
@Override
public EmpStatus getResult(ResultSet rs, String columnName)
throws SQLException {
// TODO Auto-generated method stub
//需要根据从数据库中拿到的枚举的状态码返回一个枚举对象
int code = rs.getInt(columnName);
System.out.println("从数据库中获取的状态码："+code);
EmpStatus status = EmpStatus.getEmpStatusByCode(code);
return status;
}
@Override
public EmpStatus getResult(ResultSet rs, int columnIndex)
throws SQLException {
// TODO Auto-generated method stub
int code = rs.getInt(columnIndex);
System.out.println("从数据库中获取的状态码："+code);
EmpStatus status = EmpStatus.getEmpStatusByCode(code);
return status;
}
@Override
public EmpStatus getResult(CallableStatement cs, int columnIndex)
throws SQLException {
// TODO Auto-generated method stub
int code = cs.getInt(columnIndex);
System.out.println("从数据库中获取的状态码："+code);
EmpStatus status = EmpStatus.getEmpStatusByCode(code);
return status;
}
}
配置
<typeHandlers>
<!--1、配置我们自定义的TypeHandler -->
<typeHandler handler="com.atguigu.mybatis.typehandler.MyEnumEmpStatusTypeHandler" javaType="com.atguigu.mybatis.bean.EmpStatus"/>
<!--2、也可以在处理某个字段的时候告诉MyBatis用什么类型处理器
保存：#{empStatus,typeHandler=xxxx}
查询：
<resultMap type="com.atguigu.mybatis.bean.Employee" id="MyEmp">
<id column="id" property="id"/>
<result column="empStatus" property="empStatus" typeHandler=""/>
</resultMap>
注意：如果在参数位置修改TypeHandler，应该保证保存数据和查询数据用的TypeHandler是一样的。
-->
</typeHandlers>
测试
@Test
public void testEnumUse(){
EmpStatus login = EmpStatus.LOGIN;
System.out.println("枚举的索引："+login.ordinal());
System.out.println("枚举的名字："+login.name());
System.out.println("枚举的状态码："+login.getCode());
System.out.println("枚举的提示消息："+login.getMsg());
}
/**
* 默认mybatis在处理枚举对象的时候保存的是枚举的名字：EnumTypeHandler
* 改变使用：EnumOrdinalTypeHandler：
* @throws IOException
*/
@Test
public void testEnum() throws IOException{
SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
SqlSession openSession = sqlSessionFactory.openSession();
try{
EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
Employee employee = new Employee("test_enum", "enum@atguigu.com","1");
//mapper.addEmp(employee);
//System.out.println("保存成功"+employee.getId());
//openSession.commit();
Employee empById = mapper.getEmpById(30026);
System.out.println(empById.getEmpStatus());
}finally{
openSession.close();
}
}