Mybatis【20】-- Mybatis延迟加载怎么处理？ (3)

当我们查询country的属性，但是不查询minister属性的时候：

@Test public void TestselectCountryById(){ Country country=dao.selectCountryById(1); System.out.println(country.getCid()); }

结果如下，会加载到关联对象minister，这就是侵入式延迟加载：

[service] 2018-07-17 14:32:37,959 - dao.ICountryDao.selectCountryById -724 [main] DEBUG dao.ICountryDao.selectCountryById - ==> Preparing: select cid,cname from country where cid=? [service] 2018-07-17 14:32:37,979 - dao.ICountryDao.selectCountryById -744 [main] DEBUG dao.ICountryDao.selectCountryById - ==> Parameters: 1(Integer) [service] 2018-07-17 14:32:38,170 - dao.ICountryDao.selectCountryById -935 [main] DEBUG dao.ICountryDao.selectCountryById - <== Total: 1 [service] 2018-07-17 14:32:38,171 - dao.ICountryDao.selectMinisterByCountry -936 [main] DEBUG dao.ICountryDao.selectMinisterByCountry - ==> Preparing: select mid,mname from minister where countryId=? [service] 2018-07-17 14:32:38,171 - dao.ICountryDao.selectMinisterByCountry -936 [main] DEBUG dao.ICountryDao.selectMinisterByCountry - ==> Parameters: 1(Integer) [service] 2018-07-17 14:32:38,173 - dao.ICountryDao.selectMinisterByCountry -938 [main] DEBUG dao.ICountryDao.selectMinisterByCountry - <== Total: 2 1 深度延迟加载

需要将延迟加载开关lazyLoadingEnabled开启（true），同时需要将侵入式加载开关aggressivelazyLoading关闭（false）

<settings> <setting value="true"/> <setting value="false"/> </settings>

1.当我们只查询出country的时候，只会查询country，而不会查询minister：
单元测试代码：

@Test public void TestselectCountryById(){ Country country=dao.selectCountryById(1); } [service] 2018-07-17 14:20:38,608 - dao.ICountryDao.selectCountryById -1271 [main] DEBUG dao.ICountryDao.selectCountryById - ==> Preparing: select cid,cname from country where cid=? [service] 2018-07-17 14:20:38,631 - dao.ICountryDao.selectCountryById -1294 [main] DEBUG dao.ICountryDao.selectCountryById - ==> Parameters: 1(Integer) [service] 2018-07-17 14:20:38,980 - dao.ICountryDao.selectCountryById -1643 [main] DEBUG dao.ICountryDao.selectCountryById - <== Total: 1

2.当我们访问country的属性的时候，也不会加载关联查询的minister：

@Test public void TestselectCountryById(){ Country country=dao.selectCountryById(1); System.out.println(country.getCid()); }

结果同样是：

[service] 2018-07-17 14:24:03,004 - org.apache.ibatis.transaction.jdbc.JdbcTransaction -686 [main] DEBUG org.apache.ibatis.transaction.jdbc.JdbcTransaction - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@cb51256] [service] 2018-07-17 14:24:03,030 - dao.ICountryDao.selectCountryById -712 [main] DEBUG dao.ICountryDao.selectCountryById - ==> Preparing: select cid,cname from country where cid=? [service] 2018-07-17 14:24:03,078 - dao.ICountryDao.selectCountryById -760 [main] DEBUG dao.ICountryDao.selectCountryById - ==> Parameters: 1(Integer) [service] 2018-07-17 14:24:03,160 - dao.ICountryDao.selectCountryById -842 [main] DEBUG dao.ICountryDao.selectCountryById - <== Total: 1

3.当我们查询country属性minister的时候：

@Test public void TestselectCountryById(){ Country country=dao.selectCountryById(1); System.out.println(country.getMinisters()); }

我们可以看到结果,执行了minister的查询,这个时候才是真正的加载minister查询

[service] 2018-07-17 14:26:55,913 - dao.ICountryDao.selectCountryById -1540 [main] DEBUG dao.ICountryDao.selectCountryById - ==> Preparing: select cid,cname from country where cid=? [service] 2018-07-17 14:26:55,943 - dao.ICountryDao.selectCountryById -1570 [main] DEBUG dao.ICountryDao.selectCountryById - ==> Parameters: 1(Integer) [service] 2018-07-17 14:26:56,161 - dao.ICountryDao.selectCountryById -1788 [main] DEBUG dao.ICountryDao.selectCountryById - <== Total: 1 [service] 2018-07-17 14:26:56,162 - dao.ICountryDao.selectMinisterByCountry -1789 [main] DEBUG dao.ICountryDao.selectMinisterByCountry - ==> Preparing: select mid,mname from minister where countryId=? [service] 2018-07-17 14:26:56,163 - dao.ICountryDao.selectMinisterByCountry -1790 [main] DEBUG dao.ICountryDao.selectMinisterByCountry - ==> Parameters: 1(Integer) [service] 2018-07-17 14:26:56,168 - dao.ICountryDao.selectMinisterByCountry -1795 [main] DEBUG dao.ICountryDao.selectMinisterByCountry - <== Total: 2 [Minister [mid=2, mname=bbb], Minister [mid=1, mname=aaa]] 加载方式 lazyLoadingEnabled aggressiveLazyLoading
直接加载   必须是false，默认是false   不管是什么，只要lazyLoadingEnabled是false就是直接加载  
侵入式延迟加载   必须是true   必须是true  
深度延迟加载   必须是true   必须是false，默认是false