一张图带你看懂原始dao与SQL动态代理开发的区别-Mybatis

public class Factory {
private final static Class<Factory> lock = Factory.class;
private static SqlSessionFactory sqlSessionFactory = null;
private Factory() {} public static SqlSessionFactory getSqlSessionFactory() {
synchronized (lock) {
if (sqlSessionFactory != null) {
return sqlSessionFactory;
}
//加载核心配置文件
String resource = "mybatis-config.xml";
InputStream inputStream;
try {
inputStream = Resources.getResourceAsStream(resource);
//创建SqlsessionFactory工厂
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
return null;
}
//对外提供一个工厂
return sqlSessionFactory;
}
} //对外提供一个Sqlsession会话
public static SqlSession getSession() {
if (sqlSessionFactory == null) {
getSqlSessionFactory();
}
return sqlSessionFactory.openSession();
}
}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration>
<properties resource="jdbc.properties"></properties> <!--environments元素：配置Mybatis的运行环境-->
<!--可配置多套运行环境，将SQL映射到多个不同的数据库上，但必须通过default属性指定默认运行环境-->
<environments default="development"> <!--default属性指定默认运行环境的id-->
<environment id="development"> <!-- 第一套运行环境的id-->
<transactionManager type="JDBC"></transactionManager> <!--事务管理器配置-->
<dataSource type="POOLED"> <!--数据源(连接池)配置-->
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments> <!--mappers元素：配置mapper映射器的xml映射文件 以动态代理开发为例，原始dao开发配置方法相同-->
<mappers>
<!--方式一：使用resource配置映射文件-->
<mapper resource="com/nreg/mapper/UserMapper.xml"></mapper>
<!--方式二：使用url配置映射文件-->
<mapper url="D:\Mybatis-agency-easy\src\main\java\com\nreg\mapper\UserMapper.xml"></mapper>
<!--方式三：多个映射器的使用：开启扫描-->
<package name="com.nreg.mapper"/>
</mappers>
</configuration>

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/crud?useSSL=false&serverTimezone=UTC&characterEncoding=utf-8
jdbc.username=root
jdbc.password=123456

### 设置Logger输出级别和输出目的地 ### debug更详细,如果把debug改为info，则打印出的表数据遇到字符串就不显示，此外还有log4j.log文件
log4j.rootLogger=debug,stdout ### 把日志信息输出到控制台 ###
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
#log4j.appender.stdout.Target=System.err
log4j.appender.stdout.layout=org.apache.log4j.SimpleLayout ### 把日志信息输出到文件：log4j.log ###
log4j.appender.logfile=org.apache.log4j.FileAppender
log4j.appender.logfile.File=log4j.log
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %F %p %m%n ###显示SQL语句部分 ###
#第一行：xml映射文件所在包
log4j.logger.com.nreg.sqlMap=DEBUG
log4j.logger.java.sql.Connection=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG
log4j.logger.java.sql.ResultSet=DEBUG

//增
boolean addUser(User user);
//删
boolean deleteUserById(int id);
//改
boolean updateUserById(User user);
//查:按id查一个
User getUserById(int id);
//查:查所有
List<User> getUser();

<!--增-->
<insert id="addUser" parameterType="com.nreg.bean.User" useGeneratedKeys="true" keyProperty="id">
insert into user values(null,#{username},#{password})
</insert> <!--删-->
<delete id="deleteUserById" parameterType="int">
delete from user where id = #{id}
</delete> <!--改-->
<update id="updateUserById" parameterType="com.nreg.bean.User">
update user set username = #{username},password = #{password} where id=#{id}
</update> <!--查:按id查-->
<select id="getUserById" parameterType="int" resultType="com.nreg.bean.User">
select * from user where 1=1 and id = #{id}<!--注：1=1 and：用于防止后面条件不成立造成SQL语句错误-->
</select> <!--查:查所有-->
<select id="getUser" resultType="com.nreg.bean.User">
select * from user
</select>

public class UserService { SqlSession sqlsession=null;
//增
public boolean addUser(User user) {
try {
//1.通过工厂获取会话
sqlsession= Factory.getSession();
//2.从会话中获取接口的代理对象
UserMapper userMapper=sqlsession.getMapper(UserMapper.class);
//3.通过代理对象操作数据库
userMapper.addUser(user);
//提交事务
sqlsession.commit();
return true;
} catch (Exception e) {
//回滚
if(sqlsession !=null){
sqlsession.rollback();
}
return false;
}finally{
//关闭连接,释放资源
if(sqlsession!=null){
sqlsession.close();
}
}
} //删
public boolean deleteUserById(int id) {
try {
sqlsession= Factory.getSession();
UserMapper userMapper=sqlsession.getMapper(UserMapper.class);
boolean tf=userMapper.deleteUserById(id);
sqlsession.commit();
return tf;
} catch (Exception e) {
if(sqlsession!=null){
sqlsession.rollback();
}
return false;
}finally{
if(sqlsession!=null){
sqlsession.close();
}
}
} //改
public boolean updateUserById(User user) { try {
sqlsession= Factory.getSession();
UserMapper userMapper=sqlsession.getMapper(UserMapper.class);
userMapper.updateUserById(user);
sqlsession.commit();
return true;
} catch (Exception e) {
if(sqlsession !=null){
sqlsession.rollback();
}
return false;
}finally{
if(sqlsession !=null){
sqlsession.close();
}
}
} //查:按id查一个
public User getUserById(int id) { try {
sqlsession= Factory.getSession();
UserMapper userMapper=sqlsession.getMapper(UserMapper.class);
User user = userMapper.getUserById(id);
return user; } catch (Exception e) {
if(sqlsession!=null){
sqlsession.rollback();
}
e.printStackTrace();
return null;
}finally{
if(sqlsession !=null){
sqlsession.close();
}
}
} //查:查所有
public List<User> getUser() { try {
sqlsession = Factory.getSession();
List<User> list = null;
UserMapper userMapper=sqlsession.getMapper(UserMapper.class);
list = userMapper.getUser();
return list;
} catch (Exception e) {
if(sqlsession!=null){
sqlsession.rollback();
}
return null;
}finally{
if(sqlsession !=null){
sqlsession.close();
}
}
}
}

public class UserDaoImpl implements UserDao { SqlSession sqlsession = null;
//增：
@Override
public boolean addUser(User user) {
try {
//1.通过工厂获取会话
sqlsession = Factory.getSession();
//2.通过会话操作数据库
sqlsession.insert("addUser", user);
//提交事务:增删改都需要提交事务
sqlsession.commit();
return true;
} catch (Exception e) {
//回滚
if (sqlsession != null) {
sqlsession.rollback();
}
return false;
} finally {
//关闭连接,释放资源
if (sqlsession != null) {
sqlsession.close();
}
}
} //删
@Override
public boolean deleteUserById(int id) {
try {
//1.通过工厂获取会话
sqlsession = Factory.getSession();
//2.通过会话操作数据库
sqlsession.delete("deleteUserById",id);
//3.提交事务
sqlsession.commit();
return true;
} catch (Exception e) {
if (sqlsession != null) {
//回滚
sqlsession.rollback();
}
return false;
} finally {
if (sqlsession != null) {
//关闭连接，释放资源
sqlsession.close();
}
}
} //改：
@Override
public boolean updateUserById(User user) {
try {
sqlsession = Factory.getSession();
sqlsession.update("updateUserById", user);
sqlsession.commit();
return true;
} catch (Exception e) {
if (sqlsession != null) {
sqlsession.rollback();
}
return false;
} finally {
if (sqlsession != null) {
sqlsession.close();
}
}
} //查：按id查
@Override
public User getUserById(int id) {
try {
sqlsession = Factory.getSession();
User user = sqlsession.selectOne("getUserById",id);
return user;
} catch (Exception e) {
if (sqlsession != null) {
sqlsession.rollback();
}
return null;
} finally {
if (sqlsession != null) {
sqlsession.close();
}
}
} //查：查所有
@Override
public List<User> getUser() {
try {
sqlsession = Factory.getSession();
List<User> list = sqlsession.selectList("getUser");
return list;
} catch (Exception e) {
if (sqlsession != null) {
sqlsession.rollback();
}
return null;
} finally {
if (sqlsession != null) {
sqlsession.close();
}
}
}
}