我们在上一节已经介绍过MyBatis实现用户的新增，下面我们将介绍对users数据库的其它操作。
1、实现用户数据的删除操作
1.1、UserDao接口类中用户的删除方法
//删除用户
public int deleteUser(int id);
1.2、配置UserMapper.xml文件
<!--根据id值删除用户-->
<delete id="deleteUser">
delete from users where id=#{id}
</delete>
1.3、删除操作的测试类
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.Reader;
public class Demo2 {
public static void main(String[] args) {
Reader resourceAsReader=null;
SqlSession sqlSession=null;
try {
resourceAsReader = Resources.getResourceAsReader("mybatis-config.xml");
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
SqlSessionFactory factory = builder.build(resourceAsReader);
sqlSession = factory.openSession();
//删除id为1的用户
int i = sqlSession.delete("com.fan.dao.UserDao.deleteUser",1);
sqlSession.commit();
System.out.println("删除成功"+i+"条");
} catch (IOException e) {
e.printStackTrace();
}finally {
if(sqlSession!=null){
sqlSession.close();
}
if(resourceAsReader!=null){
try {
resourceAsReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
2、实现用户数据的更新操作
2.1、UserDao接口类中用户的更新方法
//更新用户
public int updateUser(User user);
2.2、配置UserMapper.xml文件
<!--根据id更新用户信息-->
<update id="updateUser">
update users set name=#{name},sex=#{sex} where id=#{id}
</update>
2.3、更新操作的测试类
import com.fan.entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.Reader;
public class Demo3 {
public static void main(String[] args) {
Reader resourceAsReader=null;
SqlSession sqlSession=null;
User user=new User(1,"张三","女");
try {
resourceAsReader = Resources.getResourceAsReader("mybatis-config.xml");
sqlSession = new SqlSessionFactoryBuilder().build(resourceAsReader).openSession();
//更新id号为1的用户信息
int i = sqlSession.update("com.fan.dao.UserDao.updateUser", user);
sqlSession.commit();
System.out.println("更新成功"+i+"条");
} catch (IOException e) {
e.printStackTrace();
}finally {
if(sqlSession!=null){
sqlSession.close();
}
if(resourceAsReader!=null){
try {
resourceAsReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
3、根据用户id查询用户
3.1、UserDao接口类中用户的查询方法
//主键查询（根据用户id查询用户）
public User findById(int id);
3.2、配置UserMapper.xml文件
<!--根据id查询用户信息-->
<select id="findById" resultType="com.fan.entity.User">
select * from users where id=#{id}
</select>
3.3、id查询操作的测试类
import com.fan.entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.Reader;
public class Demo4 {
public static void main(String[] args) {
Reader resourceAsReader=null;
SqlSession sqlSession=null;
try {
resourceAsReader = Resources.getResourceAsReader("mybatis-config.xml");
sqlSession = new SqlSessionFactoryBuilder().build(resourceAsReader).openSession();
//查询id为1的用户
User user = sqlSession.selectOne("com.fan.dao.UserDao.findById", 1);
System.out.println(user.getName()+"..."+user.getSex());
} catch (IOException e) {
e.printStackTrace();
}finally {
if(sqlSession!=null){
sqlSession.close();
}
if(resourceAsReader!=null){
try {
resourceAsReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
4、查询数据库中所有的用户
4.1、UserDao接口类中所有用户信息查询方法
//多行查询（查询users数据库中所有用户信息）
public List<User> findAll();
4.2、配置UserMapper.xml文件
<!--查询所有用户信息-->
<select id="findAll" resultType="com.fan.entity.User">
select * from users
</select>
4.3、所有用户查询操作的测试类
import com.fan.entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.Reader;
import java.util.List;
public class Demo5 {
public static void main(String[] args) {
Reader resourceAsReader=null;
SqlSession sqlSession=null;
try {
resourceAsReader = Resources.getResourceAsReader("mybatis-config.xml");
sqlSession = new SqlSessionFactoryBuilder().build(resourceAsReader).openSession();
//查询数据库中所有用户信息
List<User> userList = sqlSession.selectList("com.fan.dao.UserDao.findAll");
for (User users:userList) {
System.out.println(users.getName()+"..."+users.getSex());
}
} catch (IOException e) {
e.printStackTrace();
}finally {
if(sqlSession!=null){
sqlSession.close();
}
if(resourceAsReader!=null){
try {
resourceAsReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
5、条件查询（根据name和sex查询用户）
5.1、UserDao接口类中条件查询方法
//条件查询（根据name和sex查询）
public User login(Map map);
5.2、配置UserMapper.xml文件
<!--条件查询（根据name和sex查询）-->
<select id="login" resultType="com.fan.entity.User">
select * from users where name=#{username} and sex=#{usersex}
</select>
5.3、条件查询操作的测试类
import com.fan.entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.Reader;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class Demo6 {
public static void main(String[] args) {
Reader resourceAsReader=null;
SqlSession sqlSession=null;
Map map=new HashMap();
map.put("username","张三");
map.put("usersex","女");
try {
resourceAsReader = Resources.getResourceAsReader("mybatis-config.xml");
sqlSession = new SqlSessionFactoryBuilder().build(resourceAsReader).openSession();
//条件查询（根据name和sex查询）
User user= sqlSession.selectOne("com.fan.dao.UserDao.login",map);
System.out.println(user.getId());
} catch (IOException e) {
e.printStackTrace();
}finally {
if(sqlSession!=null){
sqlSession.close();
}
if(resourceAsReader!=null){
try {
resourceAsReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
6、修改测试类Demo6，调用getMapper(Mapper.class)执行Mapper接口方法来实现条件查询，关键代码如下：
//条件查询（根据name和sex查询）
//User user= sqlSession.selectOne("com.fan.dao.UserDao.login",map);
UserDao userDaoMapper = sqlSession.getMapper(UserDao.class);
User loginuser = userDaoMapper.login(map);
System.out.println(loginuser.getId());
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