爲了使用起來和mybatis是一樣一樣的,名字也跟mybatis一樣,先出一個xml版本的查詢
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.bl</groupId>
<artifactId>mybatis</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.38</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13-beta-2</version>
</dependency>
<dependency>
<groupId>dom4j</groupId>
<artifactId>dom4j</artifactId>
<version>1.6.1</version>
</dependency>
<dependency>
<groupId>jaxen</groupId>
<artifactId>jaxen</artifactId>
<version>1.1.6</version>
</dependency>
</dependencies>
</project>
TestMybatis
package com.bl.myMyBatis.test;
import com.bl.domain.User;
import com.bl.myMyBatis.core.SqlSession;
import com.bl.myMyBatis.core.SqlSessionFactory;
import com.bl.myMyBatis.core.SqlSessionFactoryBuilder;
import com.bl.myMyBatis.io.Resources;
import org.junit.Test;
import java.io.InputStream;
import java.util.List;
/**
* @Deacription 測試自定義的mybatis
* @Author BarryLee
* @Date 2019/11/10 22:36
*/
public class TestMybatis {
@Test
public void test() {
InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
SqlSessionFactory factory = SqlSessionFactoryBuilder.build(in);
SqlSession session = factory.openSession();
IUserMapper mapper = session.getMapper(IUserMapper.class);
List<User> users = mapper.queryAll();
for(User user: users) {
System.out.println(user);
}
}
}
sqlMapConfig.xml
<?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">
<!-- 這是MyBatis的主配置文件 -->
<configuration>
<!-- 配置環境 -->
<environments default="mysql">
<!-- 配置mysql環境變量 -->
<environment id="mysql">
<!-- 事務類型 -->
<transactionManager type="JDBC"></transactionManager>
<!-- 數據源(連接池) -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/test"/>
<property name="username" value="root"/>
<property name="password" value="barry"/>
</dataSource>
</environment>
</environments>
<!--使用XML,這裏應該是resource-->
<mappers>
<mapper resource="com/bl/dao/IUserMapper.xml"></mapper>
</mappers>
</configuration>
IUserMapper.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.bl.dao.IUserMapper">
<select id="queryAll" resultType="com.bl.domain.User">
select * from user
</select>
</mapper>
Configuration
package com.bl.myMyBatis.config;
import java.util.HashMap;
import java.util.Map;
/**
* @Deacription TODO
* @Author BarryLee
* @Date 2019/11/10 17:40
*/
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);
}
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;
}
}
Mapper
package com.bl.myMyBatis.config;
/**
* @Deacription TODO
* @Author BarryLee
* @Date 2019/11/10 20:04
*/
public class Mapper {
private String queryString; // sql
private String resultType;
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;
}
}
DataSourceUtil
package com.bl.myMyBatis.utils;
import com.bl.myMyBatis.config.Configuration;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
/**
* @Deacription TODO
* @Author BarryLee
* @Date 2019/11/10 21:42
*/
public class DataSourceUtil {
/**
* 獲取連接,這裏沒有使用單例
* @param cfg
* @return
*/
public static Connection getConnection(Configuration cfg) {
try {
Class.forName(cfg.getDriver());
return DriverManager.getConnection(cfg.getUrl(), cfg.getUsername(), cfg.getPassword());
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
}
Executor
package com.bl.myMyBatis.utils;
import com.bl.myMyBatis.config.Mapper;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;
/**
* @Deacription 負責執行SQL語句,並且封裝結果集
* @Author BarryLee
* @Date 2019/11/10 22:15
*/
public class Executor {
public <E> List<E> selectList(Mapper mapper, Connection conn) {
PreparedStatement pstm = null;
ResultSet rs = null;
try {
//1.取出mapper中的數據
String queryString = mapper.getQueryString();//select * from user
String resultType = mapper.getResultType();//com.itheima.domain.User
Class domainClass = Class.forName(resultType);
//2.獲取PreparedStatement對象
pstm = conn.prepareStatement(queryString);
//3.執行SQL語句,獲取結果集
rs = pstm.executeQuery();
//4.封裝結果集
List<E> list = new ArrayList<E>();//定義返回值
while(rs.next()) {
//實例化要封裝的實體類對象
E obj = (E)domainClass.newInstance();
//取出結果集的元信息:ResultSetMetaData
ResultSetMetaData rsmd = rs.getMetaData();
//取出總列數
int columnCount = rsmd.getColumnCount();
//遍歷總列數
for (int i = 1; i <= columnCount; i++) {
//獲取每列的名稱,列名的序號是從1開始的
String columnName = rsmd.getColumnName(i);
//根據得到列名,獲取每列的值
Object columnValue = rs.getObject(columnName);
//給obj賦值:使用Java內省機制(藉助PropertyDescriptor實現屬性的封裝)
PropertyDescriptor pd = new PropertyDescriptor(columnName,domainClass);//要求:實體類的屬性和數據庫表的列名保持一種
//獲取它的寫入方法
Method writeMethod = pd.getWriteMethod();
//把獲取的列的值,給對象賦值
writeMethod.invoke(obj,columnValue);
}
//把賦好值的對象加入到集合中
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();
}
}
}
}
XmlConfigBuilder
package com.bl.myMyBatis.utils;
import com.bl.myMyBatis.config.Configuration;
import com.bl.myMyBatis.config.Mapper;
import org.apache.ibatis.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.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* 用於解析配置文件
*/
public class XMLConfigBuilder {
/**
* 解析主配置文件,把裏面的內容填充到DefaultSqlSession所需要的地方
* 使用的技術:
* dom4j+xpath
*/
public static Configuration loadConfiguration(InputStream config){
try{
//定義封裝連接信息的配置對象(mybatis的配置對象)
Configuration cfg = new Configuration();
//1.獲取SAXReader對象
SAXReader reader = new SAXReader();
//2.根據字節輸入流獲取Document對象
Document document = reader.read(config);
//3.獲取根節點
Element root = document.getRootElement();
//4.使用xpath中選擇指定節點的方式,獲取所有property節點
List<Element> propertyElements = root.selectNodes("//property");
//5.遍歷節點
for(Element propertyElement : propertyElements){
//判斷節點是連接數據庫的哪部分信息
//取出name屬性的值
String name = propertyElement.attributeValue("name");
if("driver".equals(name)){
//表示驅動
//獲取property標籤value屬性的值
String driver = propertyElement.attributeValue("value");
cfg.setDriver(driver);
}
if("url".equals(name)){
//表示連接字符串
//獲取property標籤value屬性的值
String url = propertyElement.attributeValue("value");
cfg.setUrl(url);
}
if("username".equals(name)){
//表示用戶名
//獲取property標籤value屬性的值
String username = propertyElement.attributeValue("value");
cfg.setUsername(username);
}
if("password".equals(name)){
//表示密碼
//獲取property標籤value屬性的值
String password = propertyElement.attributeValue("value");
cfg.setPassword(password);
}
}
//取出mappers中的所有mapper標籤,判斷他們使用了resource還是class屬性
List<Element> mapperElements = root.selectNodes("//mappers/mapper");
//遍歷集合
for(Element mapperElement : mapperElements){
//判斷mapperElement使用的是哪個屬性
Attribute attribute = mapperElement.attribute("resource");
if(attribute != null){
System.out.println("使用的是XML");
//表示有resource屬性,用的是XML
//取出屬性的值
String mapperPath = attribute.getValue();//獲取屬性的值"com/itheima/dao/IUserDao.xml"
//把映射配置文件的內容獲取出來,封裝成一個map
Map<String, Mapper> mappers = loadMapperConfiguration(mapperPath);
//給configuration中的mappers賦值
cfg.setMappers(mappers);
}
//else{
// System.out.println("使用的是註解");
// //表示沒有resource屬性,用的是註解
// //獲取class屬性的值
// String daoClassPath = mapperElement.attributeValue("class");
// //根據daoClassPath獲取封裝的必要信息
// Map<String,Mapper> mappers = loadMapperAnnotation(daoClassPath);
// //給configuration中的mappers賦值
// cfg.setMappers(mappers);
//}
}
//返回Configuration
return cfg;
}catch(Exception e){
throw new RuntimeException(e);
}finally{
try {
config.close();
}catch(Exception e){
e.printStackTrace();
}
}
}
/**
* 根據傳入的參數,解析XML,並且封裝到Map中
* @param mapperPath 映射配置文件的位置
* @return map中包含了獲取的唯一標識(key是由dao的全限定類名和方法名組成)
* 以及執行所需的必要信息(value是一個Mapper對象,裏面存放的是執行的SQL語句和要封裝的實體類全限定類名)
*/
private static Map<String,Mapper> loadMapperConfiguration(String mapperPath)throws IOException {
InputStream in = null;
try{
//定義返回值對象
Map<String,Mapper> mappers = new HashMap<String,Mapper>();
//1.根據路徑獲取字節輸入流
in = Resources.getResourceAsStream(mapperPath);
//2.根據字節輸入流獲取Document對象
SAXReader reader = new SAXReader();
Document document = reader.read(in);
//3.獲取根節點
Element root = document.getRootElement();
//4.獲取根節點的namespace屬性取值
String namespace = root.attributeValue("namespace");//是組成map中key的部分
//5.獲取所有的select節點
List<Element> selectElements = root.selectNodes("//select");
//6.遍歷select節點集合
for(Element selectElement : selectElements){
//取出id屬性的值 組成map中key的部分
String id = selectElement.attributeValue("id");
//取出resultType屬性的值 組成map中value的部分
String resultType = selectElement.attributeValue("resultType");
//取出文本內容 組成map中value的部分
String queryString = selectElement.getText();
//創建Key
String key = namespace+"."+id;
//創建Value
Mapper 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();
}
}
/**
* 根據傳入的參數,得到dao中所有被select註解標註的方法。
* 根據方法名稱和類名,以及方法上註解value屬性的值,組成Mapper的必要信息
* @param daoClassPath
* @return
private static Map<String,Mapper> loadMapperAnnotation(String daoClassPath)throws Exception{
//定義返回值對象
Map<String,Mapper> mappers = new HashMap<String, Mapper>();
//1.得到dao接口的字節碼對象
Class daoClass = Class.forName(daoClassPath);
//2.得到dao接口中的方法數組
Method[] methods = daoClass.getMethods();
//3.遍歷Method數組
for(Method method : methods){
//取出每一個方法,判斷是否有select註解
boolean isAnnotated = method.isAnnotationPresent(Select.class);
if(isAnnotated){
//創建Mapper對象
Mapper mapper = new Mapper();
//取出註解的value屬性值
Select selectAnno = method.getAnnotation(Select.class);
String queryString = selectAnno.value();
mapper.setQueryString(queryString);
//獲取當前方法的返回值,還要求必須帶有泛型信息
Type type = method.getGenericReturnType();//List<User>
//判斷type是不是參數化的類型
if(type instanceof ParameterizedType){
//強轉
ParameterizedType ptype = (ParameterizedType)type;
//得到參數化類型中的實際類型參數
Type[] types = ptype.getActualTypeArguments();
//取出第一個
Class domainClass = (Class)types[0];
//獲取domainClass的類名
String resultType = domainClass.getName();
//給Mapper賦值
mapper.setResultType(resultType);
}
//組裝key的信息
//獲取方法的名稱
String methodName = method.getName();
String className = method.getDeclaringClass().getName();
String key = className+"."+methodName;
//給map賦值
mappers.put(key,mapper);
}
}
return mappers;
}
*/
}
SqlSession
package com.bl.myMyBatis.core;
/**
* @Deacription TODO
* @Author BarryLee
* @Date 2019/11/10 16:51
*/
public interface SqlSession {
/**
* @param daoInterfaceClass
* @param <T> dao 接口字節碼
* @return
*/
<T> T getMapper(Class<T> daoInterfaceClass);
}
SqlSessionFactory
package com.bl.myMyBatis.core;
public interface SqlSessionFactory {
SqlSession openSession();
}
SqlSessionFactoryBuilder
package com.bl.myMyBatis.core;
import com.bl.myMyBatis.config.Configuration;
import com.bl.myMyBatis.utils.XMLConfigBuilder;
import java.io.InputStream;
/**
* @Deacription 構建者模式 - 創建一個工廠(這裏簡單實現,具體應該有待斟酌)
* @Author BarryLee
* @Date 2019/11/10 16:49
*/
public class SqlSessionFactoryBuilder {
public static SqlSessionFactory build(InputStream in){
Configuration cfg = XMLConfigBuilder.loadConfiguration(in);
return new DefaultSqlSessionFactory(cfg);
}
}
DefaultSqlSession
package com.bl.myMyBatis.core;
import com.bl.myMyBatis.config.Configuration;
import com.bl.myMyBatis.utils.DataSourceUtil;
import java.lang.reflect.Proxy;
import java.sql.Connection;
/**
* @Deacription TODO
* @Author BarryLee
* @Date 2019/11/10 20:56
*/
public class DefaultSqlSession implements SqlSession {
private Configuration cfg;
private Connection conn;
public DefaultSqlSession(Configuration cfg) {
this.cfg = cfg;
// 根據配置(driver,url,username,password,mappers)獲取一個連接
conn = DataSourceUtil.getConnection(cfg);
}
public <T> T getMapper(Class<T> daoInterfaceClass) {
return (T) Proxy.newProxyInstance(
daoInterfaceClass.getClassLoader(),
new Class[]{daoInterfaceClass},
new MapperProxy(cfg.getMappers(), conn)
);
}
}
package com.bl.myMyBatis.core;
import com.bl.myMyBatis.config.Configuration;
/**
* @Deacription TODO
* @Author BarryLee
* @Date 2019/11/10 20:57
*/
public class DefaultSqlSessionFactory implements SqlSessionFactory {
private Configuration cfg;
public DefaultSqlSessionFactory(Configuration cfg) {
this.cfg = cfg;
}
public SqlSession openSession() {
return new DefaultSqlSession(cfg);
}
}
MapperProxy
package com.bl.myMyBatis.core;
import com.bl.myMyBatis.config.Mapper;
import com.bl.myMyBatis.utils.Executor;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.util.Map;
/**
* @Deacription TODO
* @Author BarryLee
* @Date 2019/11/10 21:58
*/
public class MapperProxy implements InvocationHandler {
private Map<String, Mapper> mappers;
private Connection conn;
public MapperProxy(Map<String, Mapper> mappers, Connection conn) {
this.mappers = mappers;
this.conn = conn;
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
String className = method.getDeclaringClass().getName();
String methodName = method.getName();
String key = className + "." + methodName;
Mapper mapper = mappers.get(key);
if(mapper == null) {
throw new IllegalArgumentException("傳參有誤");
}
// 調用工具類執行查詢所有
return new Executor().selectList(mapper,conn);
}
}
package com.bl.myMyBatis.io;
import java.io.InputStream;
public class Resources {
/**
* 獲取inputStream
* @param path
* @return
*/
public static InputStream getResourceAsStream(String path) {
return Resources.class.getClassLoader().getResourceAsStream(path);
}
}
<?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">
<!-- 這是MyBatis的主配置文件 -->
<configuration>
<!-- 配置環境 -->
<environments default="mysql">
<!-- 配置mysql環境變量 -->
<environment id="mysql">
<!-- 事務類型 -->
<transactionManager type="JDBC"></transactionManager>
<!-- 數據源(連接池) -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/test"/>
<property name="username" value="root"/>
<property name="password" value="barry"/>
</dataSource>
</environment>
</environments>
<!--使用註解:這裏應該是class-->
<mappers>
<mapper class="com.bl.annotation.IUserDao"></mapper>
</mappers>
</configuration>