05、MyBatis 实战 - 之手写MyBatis框架简单探索版(含源代码)
1、准备工作
引入dom4j依赖，引入mysql驱动依赖
注意：因为是手写mybatis框架，所以并没有引入mybatis的相关依赖
<?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.powernode</groupId>
<artifactId>parse-xml-by-dom4j</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
<!--dom4j依赖-->
<dependency>
<groupId>org.dom4j</groupId>
<artifactId>dom4j</artifactId>
<version>2.1.3</version>
</dependency>
<dependency>
<groupId>jaxen</groupId>
<artifactId>jaxen</artifactId>
<version>1.2.0</version>
</dependency>
<!--junit测试类-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<!--数据库驱动-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.30</version>
</dependency>
</dependencies>
</project>
二、手写Mybatis思路
完全是按照mybatis查询数据库时，所需要的步骤，来创建对象，以及解析。
这是原生的mybatis查询代码：
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
InputStream ins = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(ins);
SqlSession sqlSession = sqlSessionFactory.openSession();
int insertCar = sqlSession.insert("insertCar");
System.out.println(insertCar);
接下来我们会手动去创建这些对象，来实现查询的过程
三、正式开始
1、创建工具类 Resources
作用：从类路径下加载配置文件
public class Resources {
private Resources(){
}
public static InputStream getResourceAsStream(String resource){
return ClassLoader.getSystemClassLoader().getResourceAsStream(resource);
}
}
关于工具类的几点说明：
1、工具类的构造方法 都是建议私有化
2、因为工具类中的方法都是静态的，不需要创建对象来调用
3、为了避免调用，所有的构造方法都是私有化
2、创建SqlSessionFactoryBuilder类
作用：
通过SqlSessionFactoryBuilder的build方法来解析 mybatis-config.xml文件，
从而获取SqlSessionFactory对象，以及数据源对象DataSource，
事务管理器对象Transaction，MappedStatement对象，即sql标签信息
package org.ibatis.core;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;
import org.ibatis.utils.Resources;
import javax.sql.DataSource;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* SqlSessionFactory构造器对象
* 通过SqlSessionFactoryBuilder的build方法来解析 mybatis-config.xml文件，
* 然后 构建SqlSessionFactory对象
*/
public class SqlSessionFactoryBuilder {
public SqlSessionFactoryBuilder(){
}
//通过SqlSessionFactoryBuilder的build方法来解析 mybatis-config.xml文件
// 然后 创建SqlSessionFactory对象
public SqlSessionFactory build(InputStream inputStream){
SqlSessionFactory factory = null;
//解析mybatis-config.xml文件
SAXReader saxReader = new SAXReader();
Document document = null;
try {
document = saxReader.read(inputStream);
} catch (DocumentException e) {
e.printStackTrace();
}
String xPath = "/configuration/environments";
Element environments = (Element) document.selectSingleNode(xPath);
String defaultId = environments.attributeValue("default");
xPath = "/configuration/environments/environment[@id='"+defaultId+"']";
Element environment = (Element) document.selectSingleNode(xPath);
Element transactionManagerElement= environment.element("transactionManager");
Element dataSourceElement = environment.element("dataSource");
List<String> sqlMapperXmlPaths = new ArrayList<>();
List<Node> nodes = document.selectNodes("//mapper");
nodes.forEach(n -> {
Element e = (Element) n;
String resource = e.attributeValue("resource");
sqlMapperXmlPaths.add(resource);
});
//获取数据源对象
DataSource dataSource = getDataSource(dataSourceElement);
//获取事务管理器对象，事务管理器需要数据源对象
Transaction transaction = getTransaction(transactionManagerElement,dataSource);
//获取MappedStatement对象，即sql标签信息
Map<String, MappedStatement> mappedStatement = getMappedStatement(sqlMapperXmlPaths);
//解析完成之后，构建SqlSessionFactory对象
factory = new SqlSessionFactory(transaction, mappedStatement);
return factory;
}
/**
* 解析所有的sqlMapper.xml文件，然后构建map集合
*
* @param sqlMapperXmlPaths
* @return
*/
private Map<String, MappedStatement> getMappedStatement(List<String> sqlMapperXmlPaths) {
Map<String, MappedStatement> mappedStatementMap = new HashMap<>();
sqlMapperXmlPaths.forEach(sqlMapperXmlPath ->{
//根据文件路径，去解析xml文件
try {
SAXReader saxReader = new SAXReader();
InputStream ins = Resources.getResourceAsStream(sqlMapperXmlPath);
Document document = saxReader.read(ins);
Element mapper = (Element) document.selectSingleNode("mapper");
String namespace = mapper.attributeValue("namespace");
List<Element> elements = mapper.elements();
elements.forEach(e ->{
String id = e.attributeValue("id");
String sqlId = namespace + "." + id;//生成唯一的sqlId，因为namespace是不重复的
String resultType = e.attributeValue("resultType");
String sql = e.getTextTrim();
MappedStatement statement = new MappedStatement(sql,resultType);
mappedStatementMap.put(sqlId,statement);
});
} catch (DocumentException e) {
e.printStackTrace();
}
});
return mappedStatementMap;
}
/**
* 获取数据源对象
* @param dataSourceElement
* @return
*/
private DataSource getDataSource(Element dataSourceElement) {
Map<String,String> map = new HashMap<>();
DataSource dataSource = null;
List<Element> propertyElements = dataSourceElement.elements("property");
propertyElements.forEach(p ->{
String name = p.attributeValue("name");
String value = p.attributeValue("value");
map.put(name,value);
});
//UNPOOLED POOLED JNDI
String type = dataSourceElement.attributeValue("type").trim().toUpperCase();
if(Const.UNPOOLED_DATASOURCE.equals(type)){
dataSource = new UnPooledDataSource(map.get("driver"),map.get("url"),map.get("username"),map.get("password"));
}
if (Const.POOLED_DATASOURCE.equals(type)) {
dataSource = new PooledDataSource();
}
if (Const.JNDI_DATASOURCE.equals(type)) {
dataSource = new JNDIDataSource();
}
return dataSource;
}
/**
* 获取事务管理器对象
* @param transactionManagerElement
* @param dataSource
* @return
*/
private Transaction getTransaction(Element transactionManagerElement,DataSource dataSource) {
Transaction transaction = null;
String type = transactionManagerElement.attributeValue("type").trim().toUpperCase();
if(Const.JDBC_TRANSACTION.equals(type)){
transaction = new JdbcTransaction(dataSource,false);//默认开启事务，手动提交
}
if(Const.MANAGED_TRANSACTION.equals(type)){
transaction = new ManagedTransaction();
}
return transaction;
}
}
3、创建SqlSessionFactory类
一个数据库，对应一个SqlSessionFactory对象
通过SqlSessionFactory对象获取SqlSession对象，开启会话
一个SqlSessionFactory 对象可以开启多个SqlSession会话
package org.ibatis.core;
import java.util.Map;
/**
* 一个数据库，对应一个SqlSessionFactory对象
* 通过SqlSessionFactory对象获取SqlSession对象，开启会话
* 一个SqlSessionFactory 对象可以开启多个SqlSession会话
*/
public class SqlSessionFactory {
/**
* 属性：
* 1、事务管理器:因为事务管理器是可以灵活切换的，所以应该是面向接口编程
* 2、存放SQL语句的map集合，key为 sqlId，value为sql标签信息对象
*/
//事务管理器
private Transaction transaction;
// 存放SQL标签信息的map集合
private Map<String,MappedStatement> mappedStatements;
public SqlSessionFactory(Transaction transaction, Map<String, MappedStatement> mappedStatements) {
this.transaction = transaction;
this.mappedStatements = mappedStatements;
}
public Transaction getTransaction() {
return transaction;
}
public void setTransaction(Transaction transaction) {
this.transaction = transaction;
}
public Map<String, MappedStatement> getMappedStatements() {
return mappedStatements;
}
public void setMappedStatements(Map<String, MappedStatement> mappedStatements) {
this.mappedStatements = mappedStatements;
}
/**
* 获取sql会话对象
* @return
*/
public SqlSession OpenSession(){
//开启会话前，先开启连接
transaction.openConnection();
//创建sqlSession对象
SqlSession sqlSession = new SqlSession(this);
return sqlSession;
}
}
4、创建事务管理器接口：Transaction
事务管理器接口：
所有的事务管理器都应该实现该接口
JDBC事务管理器，MANAGED事务管理器 都要实现这个接口
事务管理器，提供管理事务的方法
package org.ibatis.core;
import java.sql.Connection;
import java.sql.SQLException;
/**
* 事务管理器接口：
* 所有的事务管理器都应该实现该接口
* JDBC事务管理器，MANAGED事务管理器 都要实现这个接口
* 事务管理器，提供管理事务的方法
*/
public interface Transaction {
void commit() throws SQLException;
void rollback();
void close();
void openConnection();//开启数据库连接对象
Connection getConnection();//获取数据库连接对象
}
5、创建事务管理器接口实现类：JdbcTransaction
package org.ibatis.core;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
/**
* JDBC 事务管理器
*/
public class JdbcTransaction implements Transaction {
private DataSource dataSource;
private boolean autoCommit;//自动提交标志：（true 自动提交 ， false 不采用自动提交,也就是使用事务管理）
private Connection connection;
public JdbcTransaction(DataSource dataSource, boolean autoCommit) {
this.dataSource = dataSource;
this.autoCommit = autoCommit;
}
@Override
public void commit() {
try {
connection.commit();
} catch (SQLException e) {
e.printStackTrace();
}
}
@Override
public void rollback() {
try {
connection.rollback();
} catch (SQLException e) {
e.printStackTrace();
}
}
@Override
public void close() {
}
@Override
public void openConnection() {
if (connection == null) {
try {
connection = dataSource.getConnection();
connection.setAutoCommit(autoCommit);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
@Override
public Connection getConnection() {
return connection;
}
}
6、创建事务管理器接口实现类：ManagedTransaction
package org.ibatis.core;
import java.sql.Connection;
/**
* MANAGED 事务管理器
*/
public class ManagedTransaction implements Transaction {
@Override
public void commit() {
}
@Override
public void rollback() {
}
@Override
public void close() {
}
@Override
public void openConnection() {
}
@Override
public Connection getConnection() {
return null;
}
}
7、三种实现数据源DataSource接口的实现类
数据源实现类：PooledDataSource
package org.ibatis.core;
import javax.sql.DataSource;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.logging.Logger;
/**
* 数据源实现类：PooledDataSource
* 使用连接池对象
*/
public class PooledDataSource implements DataSource {
@Override
public Connection getConnection() throws SQLException {
return null;
}
@Override
public Connection getConnection(String username, String password) throws SQLException {
return null;
}
@Override
public <T> T unwrap(Class<T> iface) throws SQLException {
return null;
}
@Override
public boolean isWrapperFor(Class<?> iface) throws SQLException {
return false;
}
@Override
public PrintWriter getLogWriter() throws SQLException {
return null;
}
@Override
public void setLogWriter(PrintWriter out) throws SQLException {
}
@Override
public void setLoginTimeout(int seconds) throws SQLException {
}
@Override
public int getLoginTimeout() throws SQLException {
return 0;
}
@Override
public Logger getParentLogger() throws SQLFeatureNotSupportedException {
return null;
}
}
数据源实现类：UnPooledDataSource
package org.ibatis.core;
import javax.sql.DataSource;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.logging.Logger;
/**
* 数据源实现类：UnPooled
* 不使用连接池对象，每次都创建一个新的Connection连接对象
*/
public class UnPooledDataSource implements DataSource {
private String url;
private String username;
private String password;
public UnPooledDataSource(String driver, String url, String username, String password) {
try {
//注册驱动
Class.forName(driver);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
this.url = url;
this.username = username;
this.password = password;
}
@Override
public Connection getConnection() throws SQLException {
return DriverManager.getConnection(url,username,password);
}
@Override
public Connection getConnection(String username, String password) throws SQLException {
return null;
}
@Override
public <T> T unwrap(Class<T> iface) throws SQLException {
return null;
}
@Override
public boolean isWrapperFor(Class<?> iface) throws SQLException {
return false;
}
@Override
public PrintWriter getLogWriter() throws SQLException {
return null;
}
@Override
public void setLogWriter(PrintWriter out) throws SQLException {
}
@Override
public void setLoginTimeout(int seconds) throws SQLException {
}
@Override
public int getLoginTimeout() throws SQLException {
return 0;
}
@Override
public Logger getParentLogger() throws SQLFeatureNotSupportedException {
return null;
}
}
数据源实现类：JNDIDataSource
package org.ibatis.core;
import javax.sql.DataSource;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.logging.Logger;
/**
* 数据源实现类：JNDI
* 使用第三方的数据库连接池，获取Connection对象
*/
public class JNDIDataSource implements DataSource {
@Override
public Connection getConnection() throws SQLException {
return null;
}
@Override
public Connection getConnection(String username, String password) throws SQLException {
return null;
}
@Override
public <T> T unwrap(Class<T> iface) throws SQLException {
return null;
}
@Override
public boolean isWrapperFor(Class<?> iface) throws SQLException {
return false;
}
@Override
public PrintWriter getLogWriter() throws SQLException {
return null;
}
@Override
public void setLogWriter(PrintWriter out) throws SQLException {
}
@Override
public void setLoginTimeout(int seconds) throws SQLException {
}
@Override
public int getLoginTimeout() throws SQLException {
return 0;
}
@Override
public Logger getParentLogger() throws SQLFeatureNotSupportedException {
return null;
}
}
8、创建MappedStatement类，存放sql标签中的所有信息
package org.ibatis.core;
/**
* 一个SQL标签中的所有信息封装到MappedStatement对象中
*/
public class MappedStatement {
private String sql;//sql语句
private String resultType;//结果集类型，insert语句没有该值，select语句才有值
public MappedStatement() {
}
public MappedStatement(String sql, String resultType) {
this.sql = sql;
this.resultType = resultType;
}
public String getSql() {
return sql;
}
public void setSql(String sql) {
this.sql = sql;
}
public String getResultType() {
return resultType;
}
public void setResultType(String resultType) {
this.resultType = resultType;
}
}
9、创建执行sql的会话对象（核心类）
package org.ibatis.core;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.Map;
/**
* 执行sql语句的会话对象
*/
public class SqlSession {
private SqlSessionFactory factory;
public SqlSession(SqlSessionFactory factory) {
this.factory = factory;
}
//insert、
public int insert(String sqlId,Object object) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
Map<String, MappedStatement> mappedStatements = factory.getMappedStatements();
MappedStatement mappedStatement = mappedStatements.get(sqlId);
Connection connection = factory.getTransaction().getConnection();
try {
String originSql = mappedStatement.getSql();
String sql = originSql.replaceAll("#\\{[0-9A-Za-z_$]*}", "?");//转换为？
PreparedStatement preparedStatement = connection.prepareStatement(sql);
//给sql语句的? 占位符传值
int fromIndex = 0;
int index = 1;
while (true){
int i = originSql.indexOf("#",fromIndex);
if(i<0){
break;
}
int rightIndex = originSql.indexOf("}",fromIndex);
String propertyName = originSql.substring(i + 2, rightIndex).trim();
fromIndex = rightIndex + 1;
String getMethodName = "get"+propertyName.toUpperCase().charAt(0)+propertyName.substring(1);
Method declaredMethod = object.getClass().getDeclaredMethod(getMethodName);
Object propertyValue = declaredMethod.invoke(object);
preparedStatement.setString(index,propertyValue.toString());
index ++;
}
return preparedStatement.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
return 0;
}
// selectOne方法,返回单个对象
public Object selectOne(String sqlId,Object param){
Object object = null;
try {
Connection connection = factory.getTransaction().getConnection();
MappedStatement mappedStatement = factory.getMappedStatements().get(sqlId);
//dql查询语句
//select * from t_user where id ={id}
String originSql = mappedStatement.getSql();
String sql = originSql.replaceAll("#\\{[0-9A-Za-z_$]*}", "?");//# 转换为 ？
PreparedStatement preparedStatement = connection.prepareStatement(sql);
//给占位符传值（暂时不做复杂的，就只有一个占位符）
preparedStatement.setString(1,param.toString());
ResultSet rs = preparedStatement.executeQuery();
String resultType = mappedStatement.getResultType();
//从结果集中封装java对象
if (rs.next()) {
Class<?> resultTypeClass = Class.forName(resultType);
object = resultTypeClass.newInstance();//相当于 Object object = new User();
//如何给Object的属性赋值
ResultSetMetaData metaData = rs.getMetaData();
int columnCount = metaData.getColumnCount();//多少列
for (int i = 0; i < columnCount; i++) {
//column the first column is 1, the second is 2, ...
String columnName = metaData.getColumnName(i+1);
String setMethodName = "set"+columnName.toUpperCase().charAt(0)+columnName.substring(1);
Method method = resultTypeClass.getDeclaredMethod(setMethodName, String.class);
//调用set方法给对象object属性赋值
method.invoke(object,rs.getString(columnName));
}
}
} catch (Exception e) {
e.printStackTrace();
}
return object;
}
public void commit(){
try {
factory.getTransaction().commit();
} catch (SQLException e) {
e.printStackTrace();
}
}
public void rollback(){
factory.getTransaction().rollback();
}
public void close(){
factory.getTransaction().close();
}
public static void main(String[] args) {
String sql = "insert into t_car values(null,#{carNum},#{brand},#{guidePrice},#{produceTime},#{carType})";
int fromIndex = 0;
int index = 1;
while (true){
int i = sql.indexOf("#",fromIndex);
if(i<0){
break;
}
int rightIndex = sql.indexOf("}",fromIndex);
String propertyName = sql.substring(i + 2, rightIndex).trim();
fromIndex = rightIndex + 1;
index ++;
}
}
}
10、常量类Const
package org.ibatis.core;
public class Const {
/**
* 数据源连接池类型
*/
public static final String UNPOOLED_DATASOURCE = "UNPOOLED";
public static final String POOLED_DATASOURCE = "POOLED";
public static final String JNDI_DATASOURCE = "NDI";
/**
* 事务管理器类型
*/
public static final String JDBC_TRANSACTION = "JDBC";
public static final String MANAGED_TRANSACTION = "MANAGED";
}
四、测试工作
1、准备 pojo实体类User
package org.ibatis.pojo;
public class User {
private String id;
private String name;
private String age;
public User(){
}
public User(String id, String name, String age) {
this.id = id;
this.name = name;
this.age = age;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
@Override
public String toString() {
return "User{" +
"id='" + id + '\'' +
", name='" + name + '\'' +
", age='" + age + '\'' +
'}';
}
}
2、准备 mybatis-config.xml文件
<?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>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="UNPOOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/powernode?useUnicode=true&characterEncoding=utf-8"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
<environment id="mybatisDB">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatisDB?useUnicode=true&characterEncoding=utf-8"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="UserMapper.xml"/>
</mappers>
</configuration>
3、准备 UserMapper.xml文件
<?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="user">
<insert id="insertUser">
insert into t_user values(#{id},#{name},#{age})
</insert>
<select id="selectById" resultType="org.ibatis.pojo.User">
select * from t_user where id ={id}
</select>
</mapper>
4、记得在mysql中创建表t_user
/*
Navicat Premium Data Transfer
Source Server : localhost
Source Server Type : MySQL
Source Server Version : 80030
Source Host : localhost:3306
Source Schema : powernode
Target Server Type : MySQL
Target Server Version : 80030
File Encoding : 65001
Date: 06/10/2022 21:50:02
*/
SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;
-- ----------------------------
-- Table structure for t_user
-- ----------------------------
DROP TABLE IF EXISTS t_user;
CREATE TABLE t_user (
id varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NOT NULL,
name varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL,
age varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL
) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci ROW_FORMAT = Dynamic;
SET FOREIGN_KEY_CHECKS = 1;
5、写一个junit测试类
import org.ibatis.core.SqlSession;
import org.ibatis.core.SqlSessionFactory;
import org.ibatis.core.SqlSessionFactoryBuilder;
import org.ibatis.pojo.User;
import org.ibatis.utils.Resources;
import org.junit.Test;
import java.io.InputStream;
import java.lang.reflect.InvocationTargetException;
public class TestMabtis {
@Test
public void testInsert() throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
InputStream ins = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactory factory = sqlSessionFactoryBuilder.build(ins);
SqlSession sqlSession = factory.OpenSession();
User user = new User("222","jack","12");
int count = sqlSession.insert("user.insertUser", user);
System.out.println(count);
sqlSession.commit();
sqlSession.close();
}
@Test
public void testSelecOne() {
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
InputStream ins = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactory factory = sqlSessionFactoryBuilder.build(ins);
SqlSession sqlSession = factory.OpenSession();
Object object = sqlSession.selectOne("user.selectById", "222");
System.out.println(object.toString());
sqlSession.commit();
sqlSession.close();
}
}
四、总结
手写mybatis框架，主要就是与那几个重要对象相关：
SqlSessionFactoryBuilder >>> SqlSessionFactory >>> SqlSession
1、SqlSessionFactoryBuilder 对象 负责 解析 核心配置文件mybatis-config.xml，
获取到数据源信息，事务管理器信息，sql标签信息，最终返回SqlSessionFactory 对象
2、通过SqlSessionFactory对象获取SqlSession对象，开启会话
3、一个SqlSessionFactory 对象可以开启多个SqlSession会话
4、一个数据库，对应一个SqlSessionFactory对象