public static void main(String[] args)throws Exception {//1.读取配置文件InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");//2.创建SqlSessionFactory工厂SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();SqlSessionFactory factory = builder.build(in);//3.使用工厂生产SqlSession对象SqlSession session = factory.openSession();//4.使用SqlSession创建Dao接口的代理对象IUserDao userDao = session.getMapper(IUserDao.class);//5.使用代理对象执行方法List<User> users = userDao.findAll();for(User user : users){System.out.println(user);}//6.释放资源session.close();in.close();}

/*** @author 唐Sir* 使用类加载器读取配置文件的类*/
public class Resources {/*** 根据传入的参数，获取一个字节输入流* @param filePath* @return*/public static InputStream getResourceAsStream(String filePath){return Resources.class.getClassLoader().getResourceAsStream(filePath);}
}

/*** @author 唐Sir* 自定义mybatis的配置类*/
public class Configuration {private String driver;private String url;private String username;private String password;private Map<String,Mapper> mappers = new HashMap<String,Mapper>();public Map<String, Mapper> getMappers() {return mappers;}public void setMappers(Map<String, Mapper> mappers) {this.mappers.putAll(mappers);//此处需要使用追加的方式}public String getDriver() {return driver;}public void setDriver(String driver) {this.driver = driver;}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}
}

<?xml version="1.0" encoding="UTF-8"?>
<!--导入约束-->
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--mysql主配置文件-->
<configuration><!-- 配置mysql环境--><environments default="mysql"><!--default和id的值相同即可--><environment id="mysql"><!--配置事务的类型（JDBC）--><transactionManager type="JDBC"></transactionManager><!--配置数据源（连接池）--><dataSource type="POOLED"><property name="driver" value="com.mysql.cj.jdbc.Driver"/><property name="url" value="jdbc:mysql://localhost:3306/eexy_mybatis?serverTimezone=UTC&amp;useSSL=false"/><property name="username" value="root"/><property name="password" value="123456"/></dataSource></environment></environments><!--指定映射配置文件的位置 映射配置文件是指每个dao独立的配置文件--><mappers><mapper resource="dao/IUserdao.xml"/></mappers>
</configuration>

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="dao.IUserDao"><select id="findAll" resultType="domain.User">select * from user</select><insert id="saveUser" parameterType="domain.User">
-- 配置插入操作后，获取插入操作的id
insert into user(username,address,sex,birthday) values (#{username}, #{address}, #{sex}, #{birthday})<selectKey keyProperty="id" keyColumn="id" resultType="int" order="AFTER">select last_insert_id()</selectKey></insert><update id="updateUser" parameterType="domain.User">update user set username = #{username},address=#{address},sex=#{sex},birthday=#{birthday} where id = #{id}</update><update id="deleteUser" parameterType="Integer">delete from user where id=#{uId}</update><select id="getUserById" parameterType="Integer" resultType="domain.User">select * from user where id=#{uid}</select><select id="findByName" parameterType="String" resultType="domain.User">
--         select * from user where username like #{name}
--             like ? -> ?=%name%select * from user where username='%${value}%'
--         like %value%</select><select id="findTotal" resultType="int">select count(id) from user</select><select id="findByVo" parameterType="domain.QueryVo" resultType="domain.User">select * from user where username like #{user.username}</select>
</mapper>

/*** @author 唐Sir* 用于封装执行的SQL语句和结果类型的全限定类名*/
public class Mapper {private String queryString;//SQL语句private String resultType;//结果类型的全限定类名public String getQueryString() {return queryString;}public void setQueryString(String queryString) {this.queryString = queryString;}public String getResultType() {return resultType;}public void setResultType(String resultType) {this.resultType = resultType;}
}

/*** @author 唐Sir*  用于解析配置文件*/
public class XMLConfigBuilder {/*** 解析主配置文件，把里面的内容填充到DefaultSqlSession所需要的地方* 使用的技术：*      dom4j+xpath*/public static Configuration loadConfiguration(InputStream config){try{//定义封装连接信息的配置对象（mybatis的配置对象）Configuration cfg = new Configuration();//1.获取SAXReader对象SAXReader reader = new SAXReader();//2.根据字节输入流获取Document对象Document document = reader.read(config);//3.获取根节点Element root = document.getRootElement();//4.使用xpath中选择指定节点的方式，获取所有property节点List<Element> propertyElements = root.selectNodes("//property");//5.遍历节点for(Element propertyElement : propertyElements){//判断节点是连接数据库的哪部分信息//取出name属性的值String name = propertyElement.attributeValue("name");if("driver".equals(name)){//表示驱动//获取property标签value属性的值String driver = propertyElement.attributeValue("value");cfg.setDriver(driver);}if("url".equals(name)){//表示连接字符串//获取property标签value属性的值String url = propertyElement.attributeValue("value");cfg.setUrl(url);}if("username".equals(name)){//表示用户名//获取property标签value属性的值String username = propertyElement.attributeValue("value");cfg.setUsername(username);}if("password".equals(name)){//表示密码//获取property标签value属性的值String password = propertyElement.attributeValue("value");cfg.setPassword(password);}}//取出mappers中的所有mapper标签，判断他们使用了resource还是class属性List<Element> mapperElements = root.selectNodes("//mappers/mapper");//遍历集合for(Element mapperElement : mapperElements){//判断mapperElement使用的是哪个属性Attribute attribute = mapperElement.attribute("resource");if(attribute != null){System.out.println("使用的是XML");//表示有resource属性，用的是XML//取出属性的值String mapperPath = attribute.getValue();//获取属性的值"com/itheima/dao/IUserDao.xml"//把映射配置文件的内容获取出来，封装成一个mapMap<String,Mapper> mappers = loadMapperConfiguration (mapperPath);//给configuration中的mappers赋值cfg.setMappers(mappers);}else{System.out.println("使用的是注解");//表示没有resource属性，用的是注解//获取class属性的值String daoClassPath = mapperElement.attributeValue("class");//根据daoClassPath获取封装的必要信息Map<String,Mapper> mappers = loadMapperAnnotation(daoClassPath);//给configuration中的mappers赋值cfg.setMappers(mappers);}}//返回Configurationreturn cfg;}catch(Exception e){throw new RuntimeException(e);}finally{try {config.close();}catch(Exception e){e.printStackTrace();}}}/*** 根据传入的参数，解析XML，并且封装到Map中* @param mapperPath    映射配置文件的位置* @return  map中包含了获取的唯一标识（key是由dao的全限定类名和方法名组成）*          以及执行所需的必要信息（value是一个Mapper对象，里面存放的是执行的SQL语句和要封装的实体类全限定类名）*/private static Map<String,Mapper> loadMapperConfiguration(String mapperPath)throws IOException {InputStream in = null;try{//定义返回值对象Map<String,Mapper> mappers = new HashMap<String,Mapper>();//1.根据路径获取字节输入流in = Resources.getResourceAsStream(mapperPath);//2.根据字节输入流获取Document对象SAXReader reader = new SAXReader();Document document = reader.read(in);//3.获取根节点Element root = document.getRootElement();//4.获取根节点的namespace属性取值String namespace = root.attributeValue("namespace");//是组成map中key的部分//5.获取所有的select节点List<Element> selectElements = root.selectNodes("//select");//6.遍历select节点集合for(Element selectElement : selectElements){//取出id属性的值      组成map中key的部分String id = selectElement.attributeValue("id");//取出resultType属性的值  组成map中value的部分String resultType = selectElement.attributeValue("resultType");//取出文本内容            组成map中value的部分String queryString = selectElement.getText();//创建KeyString key = namespace+"."+id;//创建ValueMapper mapper = new Mapper();mapper.setQueryString(queryString);mapper.setResultType(resultType);//把key和value存入mappers中mappers.put(key,mapper);}return mappers;}catch(Exception e){throw new RuntimeException(e);}finally{in.close();}}/*** 根据传入的参数，得到dao中所有被select注解标注的方法。* 根据方法名称和类名，以及方法上注解value属性的值，组成Mapper的必要信息* @param daoClassPath* @return*/private static Map<String,Mapper> loadMapperAnnotation(String daoClassPath)throws Exception{//定义返回值对象Map<String,Mapper> mappers = new HashMap<String, Mapper>();//1.得到dao接口的字节码对象Class daoClass = Class.forName(daoClassPath);//2.得到dao接口中的方法数组Method[] methods = daoClass.getMethods();//3.遍历Method数组for(Method method : methods){//取出每一个方法，判断是否有select注解boolean isAnnotated = method.isAnnotationPresent(Select.class);if(isAnnotated){//创建Mapper对象Mapper mapper = new Mapper();//取出注解的value属性值Select selectAnno = method.getAnnotation(Select.class);String queryString = selectAnno.value();mapper.setQueryString(queryString);//获取当前方法的返回值，还要求必须带有泛型信息Type type = method.getGenericReturnType();//List<User>//判断type是不是参数化的类型if(type instanceof ParameterizedType){//强转ParameterizedType ptype = (ParameterizedType)type;//得到参数化类型中的实际类型参数Type[] types = ptype.getActualTypeArguments();//取出第一个Class domainClass = (Class)types[0];//获取domainClass的类名String resultType = domainClass.getName();//给Mapper赋值mapper.setResultType(resultType);}//组装key的信息//获取方法的名称String methodName = method.getName();String className = method.getDeclaringClass().getName();String key = className+"."+methodName;//给map赋值mappers.put(key,mapper);}}return mappers;}
}

/*** @author 唐Sir* 用于创建数据源的工具类*/
public class DataSourceUtil {/*** 用于获取一个连接* @param cfg* @return*/public static Connection getConnection(Configuration cfg){try {Class.forName(cfg.getDriver());return DriverManager.getConnection(cfg.getUrl(), cfg.getUsername(), cfg.getPassword());}catch(Exception e){throw new RuntimeException(e);}}
}

public class SqlSessionFactoryBuilder {/*** 根据参数的字节输入流来构建一个SqlSessionFactory工厂*/public SqlSessionFactory build(InputStream config){Configuration cfg = XMLConfigBuilder.loadConfiguration(config);return  new DefaultSqlSessionFactory(cfg);}
}

public class DefaultSqlSessionFactory implements SqlSessionFactory{private Configuration cfg;public DefaultSqlSessionFactory(Configuration cfg){this.cfg = cfg;}/*** 用于创建一个新的操作数据库对象* @return*/@Overridepublic SqlSession openSession() {return new DefaultSqlSession(cfg);}
}
}

/*** 自定义Mybatis中和数据库交互的核心类*  它里面可以创建dao接口的代理对象*/
public interface SqlSession {/*** 根据参数创建一个代理对象* @param daoInterfaceClass dao的接口字节码*/<T> T getMapper(Class<T> daoInterfaceClass);/*** 释放资源*/void close();
}

public class DefaultSqlSession implements SqlSession {private Configuration cfg;private Connection connection;public DefaultSqlSession(Configuration cfg){this.cfg = cfg;connection = DataSourceUtil.getConnection(cfg);}/*** 用于创建代理对象* @param daoInterfaceClass dao的接口字节码* @param <T>* @return*/@Overridepublic <T> T getMapper(Class<T> daoInterfaceClass) {return (T) Proxy.newProxyInstance(daoInterfaceClass.getClassLoader(),new Class[]{daoInterfaceClass},new MapperProxy(cfg.getMappers(),connection));}/*** 用于释放资源*/@Overridepublic void close() {if(connection != null) {try {connection.close();} catch (Exception e) {e.printStackTrace();}}}
}

public class DataSourceUtil {/*** 用于获取一个连接* @param cfg* @return*/public static Connection getConnection(Configuration cfg){try {Class.forName(cfg.getDriver());return DriverManager.getConnection(cfg.getUrl(), cfg.getUsername(), cfg.getPassword());}catch(Exception e){throw new RuntimeException(e);}}
}

public class Mapper {private String queryString;//SQL查询语句private String resultType;//结果对象的全限定类名public String getQueryString() {return queryString;}public void setQueryString(String queryString) {this.queryString = queryString;}public String getResultType() {return resultType;}public void setResultType(String resultType) {this.resultType = resultType;}
}

public class MapperProxy implements InvocationHandler {//map的key是全限定类名+方法名private Map<String,Mapper> mappers;private Connection conn;public MapperProxy(Map<String,Mapper> mappers,Connection conn){this.mappers = mappers;this.conn = conn;}/*** 用于对方法进行增强的，我们的增强其实就是调用selectList方法*/@Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {//1.获取方法名String methodName = method.getName();//2.获取方法所在类的名称String className = method.getDeclaringClass().getName();//3.组合keyString key = className+"."+methodName;//4.获取mappers中的Mapper对象Mapper mapper = mappers.get(key);//5.判断是否有mapperif(mapper == null){throw new IllegalArgumentException("传入的参数有误");}//6.调用工具类执行查询所有return new Executor().selectList(mapper,conn);}
}

/*** @author 唐Sir* 负责执行SQL语句，并且封装结果集*/
public class Executor {public <E> List<E> selectList(Mapper mapper, Connection conn) {PreparedStatement pstm = null;ResultSet rs = null;try {//1.取出mapper中的数据String queryString = mapper.getQueryString();//select * from userString resultType = mapper.getResultType();//com.itheima.domain.UserClass domainClass = Class.forName(resultType);//2.获取PreparedStatement对象pstm = conn.prepareStatement(queryString);//3.执行SQL语句，获取结果集rs = pstm.executeQuery();//4.封装结果集List<E> list = new ArrayList<E>();//定义返回值while(rs.next()) {//实例化要封装的实体类对象E obj = (E)domainClass.newInstance();//取出结果集的元信息：ResultSetMetaDataResultSetMetaData rsmd = rs.getMetaData();//取出总列数int columnCount = rsmd.getColumnCount();//遍历总列数for (int i = 1; i <= columnCount; i++) {//获取每列的名称，列名的序号是从1开始的String columnName = rsmd.getColumnName(i);//根据得到列名，获取每列的值Object columnValue = rs.getObject(columnName);//给obj赋值：使用Java内省机制（借助PropertyDescriptor实现属性的封装）PropertyDescriptor pd = new PropertyDescriptor (columnName, domainClass) ;//要求：实体类的属性和数据库表的列名保持一种//获取它的写入方法Method writeMethod = pd.getWriteMethod();//把获取的列的值，给对象赋值writeMethod.invoke(obj,columnValue);}//把赋好值的对象加入到集合中list.add(obj);}return list;} catch (Exception e) {throw new RuntimeException(e);} finally {release(pstm,rs);}}private void release(PreparedStatement pstm,ResultSet rs){if(rs != null){try {rs.close();}catch(Exception e){e.printStackTrace();}}if(pstm != null){try {pstm.close();}catch(Exception e){e.printStackTrace();}}}
}