自定义MyBatis

//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UserDao userDao = session.getMapper(UserDao.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();

<?xml version="1.0" encoding="utf-8" ?><!DOCTYPE configuration>
<configuration>    <!--配置环境-->    <environments default="mysql">        <!--配置mysql的环境-->        <environment id="mysql">            <!--配置事务类型-->            <transactionManager type="JDBC"></transactionManager>            <!--配置数据源（连接池）-->            <dataSource type="POOLED">                <!--配置连接数据库的基本信息-->                <property name="driver" value="com.mysql.jdbc.Driver"/>                <property name="url"                          value="jdbc:mysql://localhost:3306/mybatis?useUnicode=true&amp;characterEncoding=utf8"/>                <property name="username" value="root"/>                <property name="password" value="1234"/>            </dataSource>        </environment>    </environments>
    <!--指定映射配置文件的位置，映射配置文件指的是每个dao独立的配置文件-->    <!--<mappers>        <mapper resource="com/jinke/dao/UserDao.xml"/>    </mappers>-->    <!--如果是用注解来配置-->    <mappers>        <mapper class="com.jinke.dao.UserDao"/>    </mappers></configuration>

import java.io.InputStream;
/*使用类加载器读取配置文件的类*/public class Resources {
    public static InputStream getResourceAsStream(String filePath) {        return Resources.class.getClassLoader().getResourceAsStream(filePath);    }}

import com.jinke.mybatis.cfg.Configuration;import com.jinke.mybatis.sqlsession.defaults.DefaultSqlSessionFactory;import com.jinke.mybatis.utils.XMLConfigBuilder;
import java.io.InputStream;
public class SqlSessionFactoryBuilder {    public SqlSessionFactory build(InputStream config) {        Configuration cfg = XMLConfigBuilder.loadConfiguration(config);        return new DefaultSqlSessionFactory(cfg);    }}

import com.jinke.mybatis.annotations.Select;import com.jinke.mybatis.cfg.Configuration;import com.jinke.mybatis.cfg.Mapper;import com.jinke.mybatis.io.Resources;import org.dom4j.Attribute;import org.dom4j.Document;import org.dom4j.Element;import org.dom4j.io.SAXReader;
import java.io.IOException;import java.io.InputStream;import java.lang.reflect.Method;import java.lang.reflect.ParameterizedType;import java.lang.reflect.Type;import java.util.HashMap;import java.util.List;import java.util.Map;
public class XMLConfigBuilder {    public static Configuration loadConfiguration(InputStream config) {        Configuration cfg = new Configuration();        try {
            SAXReader reader = new SAXReader();
            Document document = reader.read(config);
            Element root = document.getRootElement();            List<Element> propertyElements = root.selectNodes("//property");
            for (Element propertyElement : propertyElements) {                String name = propertyElement.attributeValue("name");                if ("driver".equals(name)) {                    String driver = propertyElement.attributeValue("value");                    cfg.setDriver(driver);                }                if ("url".equals(name)) {                    String url = propertyElement.attributeValue("value");                    cfg.setUrl(url);                }                if ("username".equals(name)) {                    String username = propertyElement.attributeValue("value");                    cfg.setUsername(username);                }                if ("password".equals(name)) {                    String password = propertyElement.attributeValue("value");                    cfg.setPassword(password);                }            }            List<Element> mapperElements = root.selectNodes("//mappers/mapper");            for (Element mapperElement : mapperElements) {                Attribute attribute = mapperElement.attribute("resource");                if (attribute != null) {                    System.out.println("使用的是XML");                    String mapperPath = attribute.getValue();                    Map<String, Mapper> mappers = loadMapperConfiguration(mapperPath);                    cfg.setMappers(mappers);                } else {                    System.out.println("使用的是注解");                    String daoClassPath = mapperElement.attributeValue("class");                    Map<String, Mapper> mappers = loadMapperAnnotation(daoClassPath);                    cfg.setMappers(mappers);                }            }            return cfg;        } catch (Exception e) {            e.printStackTrace();        } finally {            try {                config.close();            } catch (IOException e) {                e.printStackTrace();            }        }        return cfg;    }
    private static Map<String, Mapper> loadMapperConfiguration(String mapperPath) throws IOException {        InputStream in = null;        Map<String, Mapper> mappers = new HashMap<String, Mapper>();        try {            in = Resources.getResourceAsStream(mapperPath);            SAXReader reader = new SAXReader();            Document document = reader.read(in);            Element root = document.getRootElement();            String namespace = root.attributeValue("namespace");            List<Element> selectElements = root.selectNodes("//select");            for (Element selectElement : selectElements) {                String id = selectElement.attributeValue("id");                String resultType = selectElement.attributeValue("resultType");                String queryString = selectElement.getText();                String key = namespace + "." + id;                Mapper mapper = new Mapper();                mapper.setQueryString(queryString);                mapper.setResultType(resultType);                mappers.put(key, mapper);            }            return mappers;        } catch (Exception e) {            e.printStackTrace();        }        return mappers;    }
    private static Map<String, Mapper> loadMapperAnnotation(String daoClassPath) throws Exception {        Map<String, Mapper> mappers = new HashMap<String, Mapper>();        Class daoClass = Class.forName(daoClassPath);        Method[] methods = daoClass.getMethods();        for (Method method : methods) {            boolean isAnnotated = method.isAnnotationPresent(Select.class);            if (isAnnotated) {                Mapper mapper = new Mapper();                Select selectAnno = method.getAnnotation(Select.class);                String queryString = selectAnno.value();                mapper.setQueryString(queryString);                Type type = method.getGenericReturnType();                if (type instanceof ParameterizedType) {                    ParameterizedType ptype = (ParameterizedType) type;                    Type[] types = ptype.getActualTypeArguments();                    Class domainClass = (Class) types[0];                    String resultType = domainClass.getName();                    mapper.setResultType(resultType);                }                String methodName = method.getName();                String className = method.getDeclaringClass().getName();                String key = className + "." + methodName;                mappers.put(key, mapper);            }        }        return mappers;    }}

import com.jinke.mybatis.cfg.Configuration;import com.jinke.mybatis.sqlsession.SqlSession;import com.jinke.mybatis.sqlsession.SqlSessionFactory;
public class DefaultSqlSessionFactory implements SqlSessionFactory {
    private Configuration cfg;
    public DefaultSqlSessionFactory(Configuration cfg) {        this.cfg = cfg;    }
    public SqlSession openSession() {        return new DefaultSqlSession(cfg);    }}

import com.jinke.mybatis.cfg.Configuration;import com.jinke.mybatis.sqlsession.SqlSession;import com.jinke.mybatis.sqlsession.proxy.MapperProxy;import com.jinke.mybatis.utils.DataSourceUtil;
import java.lang.reflect.Proxy;import java.sql.Connection;import java.sql.SQLException;
public class DefaultSqlSession implements SqlSession {
    private Configuration cfg;    private Connection connection;
    public DefaultSqlSession(Configuration cfg) {        this.cfg = cfg;        this.connection = DataSourceUtil.getConnection(cfg);    }
    public <T> T getMapper(Class<T> daoInterfaceClass) {        return (T) Proxy.newProxyInstance(daoInterfaceClass.getClassLoader(), new Class[]{daoInterfaceClass}, new MapperProxy(cfg.getMappers(), connection));    }
    public void close() {        if (connection != null) {            try {                connection.close();            } catch (SQLException e) {                e.printStackTrace();            }        }    }}

import com.jinke.mybatis.cfg.Mapper;import com.jinke.mybatis.utils.Executor;
import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.sql.Connection;import java.util.Map;
public class MapperProxy implements InvocationHandler {
    private Map<String, Mapper> mappers;    private Connection connection;
    public MapperProxy(Map<String, Mapper> mappers, Connection connection) {        this.mappers = mappers;        this.connection = connection;    }
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {        String methodName = method.getName();        String className = method.getDeclaringClass().getName();        String key = className + "." + methodName;        Mapper mapper = mappers.get(key);        if (mapper == null) {            throw new IllegalArgumentException("传入的参数有误");        }        return new Executor().selectList(mapper, connection);    }}

import com.jinke.mybatis.cfg.Mapper;
import java.beans.PropertyDescriptor;import java.lang.reflect.Method;import java.sql.*;import java.util.ArrayList;import java.util.List;
public class Executor {    public <E> List<E> selectList(Mapper mapper, Connection conn) {        PreparedStatement pstm = null;        ResultSet rs = null;        try {            String queryString = mapper.getQueryString();            String resultType = mapper.getResultType();            Class domainClass = Class.forName(resultType);            pstm = conn.prepareStatement(queryString);            rs = pstm.executeQuery();            List<E> list = new ArrayList<E>();            while (rs.next()) {                E obj = (E) domainClass.newInstance();                ResultSetMetaData rsmd = rs.getMetaData();                int columnCount = rsmd.getColumnCount();                for (int i = 1; i < columnCount; i++) {                    String columnName = rsmd.getColumnName(i);                    Object columnValue = rs.getObject(columnName);                    PropertyDescriptor pd = new PropertyDescriptor(columnName, domainClass);                    Method writeMethod = pd.getWriteMethod();                    writeMethod.invoke(obj, columnValue);                }                list.add(obj);            }            return list;        } catch (Exception e) {            e.printStackTrace();        } finally {            release(pstm, rs);        }        return null;    }
    private void release(PreparedStatement pstm, ResultSet rs) {        if (rs != null) {            try {                rs.close();            } catch (SQLException e) {                e.printStackTrace();            }        }
        if (pstm != null) {            try {                pstm.close();            } catch (SQLException e) {                e.printStackTrace();            }        }    }}