一级缓存，在开启sqlSession后会自动开启，关闭sqlSession，就可以关闭一级缓存
1.查询相同的数据，不会刷新缓存
例子
public void getUserById (){
SqlSession sqlSession = sqlSessionFactory.getsqlSession();
userMapper mapper = sqlSession.getMapper(userMapper.class);
user user1 = mapper.getUserById(2);
System.out.println(user1);
System.out.println("=========");
user user2 = mapper.getUserById(2);
System.out.println(user2);
sqlSession.close();
}
结果
Opening JDBC Connection
Created connection 454884231.
Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@1b1cfb87]
==> Preparing: select * from user where id=?
==> Parameters: 2(Integer)
<== Columns: id, name, pwd
<== Row: 2, 小落, 12341234
<== Total: 1
com.Google.pojo.user@19b89d4
=========
com.Google.pojo.user@19b89d4
Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@1b1cfb87]
Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@1b1cfb87]
Returned connection 454884231 to pool.
2.当执行 增 删 改 命令时，会刷新缓存
例子
public void getUserById (){
SqlSession sqlSession = sqlSessionFactory.getsqlSession();
userMapper mapper = sqlSession.getMapper(userMapper.class);
user user1 = mapper.getUserById(2);//查找用户
System.out.println(user1);
int i = mapper.updateUser(new user(2, "aaa", "bbb"));//修改用户
if(i>0){
sqlSession.commit();
}else{
sqlSession.rollback();
}
System.out.println("=========");
user user2 = mapper.getUserById(2);
System.out.println(user2);
sqlSession.close();
}
运行结果
Opening JDBC Connection
Created connection 136393487.
Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@821330f]
==> Preparing: select * from user where id=?
==> Parameters: 2(Integer)
<== Columns: id, name, pwd
<== Row: 2, 小落, 12341234
<== Total: 1
user(id=2, name=小落, pwd=12341234)
==> Preparing: update user set name = ?,pwd = ? where id=?
==> Parameters: aaa(String), bbb(String), 2(Integer)
<== Updates: 1
=========
==> Preparing: select * from user where id=?
==> Parameters: 2(Integer)
<== Columns: id, name, pwd
<== Row: 2, aaa, bbb
<== Total: 1
user(id=2, name=aaa, pwd=bbb)
Rolling back JDBC Connection [com.mysql.jdbc.JDBC4Connection@821330f]
Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@821330f]
Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@821330f]
Returned connection 136393487 to pool.
这里我们可以清楚的看到，即使是查询两次相同的结果，缓存还是刷新了。这是因为更新了数据库，所有得强制刷新缓存，要不然，得到的数据就是旧数据
3.手动刷新缓存
public void getUserById (){
SqlSession sqlSession = sqlSessionFactory.getsqlSession();
userMapper mapper = sqlSession.getMapper(userMapper.class);
user user1 = mapper.getUserById(2);//查找用户
System.out.println(user1);
sqlSession.clearCache();//刷新缓存
System.out.println("=========");
user user2 = mapper.getUserById(2);
System.out.println(user2);
sqlSession.close();
}
运行结果
Opening JDBC Connection
Created connection 136393487.
Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@821330f]
==> Preparing: select * from user where id=?
==> Parameters: 2(Integer)
<== Columns: id, name, pwd
<== Row: 2, aaa, bbb
<== Total: 1
user(id=2, name=aaa, pwd=bbb)
=========
==> Preparing: select * from user where id=?
==> Parameters: 2(Integer)
<== Columns: id, name, pwd
<== Row: 2, aaa, bbb
<== Total: 1
user(id=2, name=aaa, pwd=bbb)
Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@821330f]
Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@821330f]
Returned connection 136393487 to pool.
这里用于手动刷新了缓存，所以出现了两个sql