简介
- 我们知道创建Maven项目后,在项目中的pom.xml配置文件中引入MyBatis依赖之后,我们就可以使用MyBatis相关的类和接口和相应的功能。
- 但为了对MyBatis的体系结构和功能有更加深刻的理解和全面的认识,本文Maven项目中的pom.xml配置文件将不再引入MyBatis依赖,转而通过自定义编写MyBatis相关的类和接口来实现同样的功能。
- MyBatis相关类和接口的介绍流程按照 测试类 中的操作步骤为顺序,先用到的类和接口先出现。
思维导图
环境搭建
Maven项目依赖
- 在pom.xml 文件中,并不引入MyBatis框架的依赖:
- mysql-connector-java(数据库连接)
- junit (单元测试)
- log4j(日志文件)
- dom4j(解析xml文件)
- jaxen(dom4j的依赖)
<?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>cn.water</groupId>
<artifactId>section02_MyPom</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.6</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.10</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.12</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>
创建数据库
#创建数据库
CREATE DATABASE mybatis;
USE mybatis;
#创建表
CREATE TABLE USER(
id INT(11) PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(32) NOT NULL COMMENT '用户名称',
birthday DATETIME DEFAULT NULL COMMENT '生日',
sex CHAR(1) DEFAULT NULL COMMENT '性别',
address VARCHAR(256) DEFAULT NULL COMMENT '地址'
) ENGINE = INNODB DEFAULT CHARSET = utf8;
#插入数据
INSERT INTO USER VALUES
(41,'老王','2018-02-27 17:47:08','男','北京'),
(42,'小二王','2018-03-02 15:09:37','女','北京金燕龙'),
(43,'小二王','2018-03-04 11:34:34','女','北京金燕龙'),
(45,'传智播客','2018-03-04 12:04:06','男','北京金燕龙'),
(46,'老王','2018-03-07 17:37:26','男','北京'),
(48,'小马宝莉','2018-03-08 11:44:00','女','北京修正');
目录结构
- src/main
- java
- cn/water/dao
- UserAnnoDao.java(持久层接口)
- UserDao.java(持久层接口)
- cn/water/domain
- cn/water/mybatis
- cfg
- Configuration.java(实体类)
- Mapper.java(实体类)
- defaults
- DeaultSqlSession.java(产品实现类)
- DeaultSqlSessionFactory.java(工厂实现类)
- io
- Resources.java(AsStream类)
- proxy
- session
- SqlSession.java(产品接口)
- SqlSessionFactory.java(工厂接口)
- SqlSessionFactoryBuilder.java(工厂构建者)
- Utils
- DataSourceUtil.java(数据库连接对象工具类)
- Executor.java(数据库操作工具类)
- XMLConfigBuilder.java(封装信息工具类)
- resources
- cn/water/dao
- UserDao.xml(持久层接口的映射配置文件)
- SqlMapConfig.xml(MyBatis主配置文件)
- src/tese
- pom.xml
数据库表
#创建数据库
CREATE DATABASE eesy_mybatis;
USE eesy_mybatis;
#创建表
CREATE TABLE USER(
id INT(11) PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(32) NOT NULL COMMENT '用户名称',
birthday DATETIME DEFAULT NULL COMMENT '生日',
sex CHAR(1) DEFAULT NULL COMMENT '性别',
address VARCHAR(256) DEFAULT NULL COMMENT '地址'
) ENGINE = INNODB DEFAULT CHARSET = utf8;
#插入数据
INSERT INTO USER VALUES
(41,'老王','2018-02-27 17:47:08','男','北京'),
(42,'小二王','2018-03-02 15:09:37','女','北京金燕龙'),
(43,'小二王','2018-03-04 11:34:34','女','北京金燕龙'),
(45,'传智播客','2018-03-04 12:04:06','男','北京金燕龙'),
(46,'老王','2018-03-07 17:37:26','男','北京'),
(48,'小马宝莉','2018-03-08 11:44:00','女','北京修正');
MyBatis主配置文件
- 提取 MyBatis主配置文件中映射信息的方式是读取 mapper标签的属性,所以 mappers 标签中最好只设置一种 mapper标签,resource 或是 class。
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">
<configuration>
<environments default="mysql">
<environment id="mysql">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper class="cn.water.dao.UserAnnoDao"></mapper>
</mappers>
</configuration>
映射配置文件
UserDao.java
<?xml version="1.0" encoding="UTF-8"?>
<mapper namespace="cn.water.dao.UserDao">
<select id="findAll" resultType="cn.water.domain.User">
SELECT * FROM user;
</select>
</mapper>
实体类
User.java
package cn.water.domain;
import java.io.Serializable;
import java.util.Date;
public class User implements Serializable {
private Integer id;
private String username;
private Date birthday;
private String sex;
private String address;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", birthday=" + birthday +
", sex='" + sex + '\'' +
", address='" + address + '\'' +
'}';
}
}
持久层接口
UserDao.java
package cn.water.dao;
import cn.water.domain.User;
import java.util.List;
public interface UserDao {
List<User> findAll();
}
UserAnnoDao.java
package cn.water.dao;
import cn.water.Anno.Select;
import cn.water.domain.User;
import java.util.List;
public interface UserAnnoDao {
@Select("SELECT * FROM user;")
List<User> findAll();
}
Mapper实体类
Mapper.java
package cn.water.mybatis.cfg;
public class Mapper {
private String queryString;
private String resultType;
@Override
public String toString() {
return "Mapper{" +
"queryString='" + queryString + '\'' +
", resultType='" + 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;
}
}
Configuration实体类
- 封装了 数据库连接信息+映射信息 的实体类
- 成员变量
- 数据库连接信息
- drive
- URL
- username
- password
- 映射信息
Configuration.java
package cn.water.mybatis.cfg;
import java.util.HashMap;
import java.util.Map;
public class Configuration {
private String driver;
private String url;
private String username;
private String password;
private Map<String,Mapper> mappers = new HashMap<String, Mapper>();
@Override
public String toString() {
return "Configuration{" +
"driver='" + driver + '\'' +
", url='" + url + '\'' +
", username='" + username + '\'' +
", password='" + password + '\'' +
", mappers=" + mappers +
'}';
}
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;
}
}
**MyBatisTest测试类
MybatisTest.java
package cn.water.test;
import cn.water.dao.UserDao;
import cn.water.domain.User;
import cn.water.mybatis.io.Resources;
import cn.water.mybatis.session.SqlSession;
import cn.water.mybatis.session.SqlSessionFactory;
import cn.water.mybatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class MybatisTest {
public static void main(String[] args) throws IOException {
InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
SqlSessionFactory factory = builder.build(inputStream);
SqlSession sqlSession = factory.openSession();
UserDao dao = sqlSession.getMapper(UserDao.class);
List<User> list = dao.findAll();
for (User user : list) {
System.out.println(user);
}
sqlSession.close();
inputStream.close();
}
}
Resources
- 输入 “SqlMapConfig.xml”,返回 InputStream
Resources.java
package cn.water.mybatis.io;
import java.io.InputStream;
public class Resources {
public static InputStream getResourceAsStream(String filePath) {
return Resources.class.getClassLoader().getResourceAsStream(filePath);
}
}
SqlSessionFactoryBuilder工厂构建者
- 返回 DefaultSqlSessionFactory工厂实现类
SqlSessionFactoryBuilder.java
package cn.water.mybatis.session;
import cn.water.mybatis.Utils.XMLConfigBuilder;
import cn.water.mybatis.cfg.Configuration;
import cn.water.mybatis.defaults.DefaultSqlSessionFactory;
import java.io.InputStream;
public class SqlSessionFactoryBuilder {
public SqlSessionFactory build(InputStream config) {
Configuration configuration = XMLConfigBuilder.loadConfiguration(config);
return new DefaultSqlSessionFactory(configuration);
}
}
XMLConfigBuilder工具类
- 工具类直接使用即可!
- 用于解析MyBatis主配置文件、xml映射配置文件、存在注释的持久层接口,并将数据封装至 Configuration实体类中。
XMLConfigBuilder.java
package cn.water.mybatis.Utils;
import cn.water.Anno.Select;
import cn.water.mybatis.io.Resources;
import cn.water.mybatis.cfg.Configuration;
import cn.water.mybatis.cfg.Mapper;
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){
try{
Configuration cfg = new Configuration();
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){
throw new RuntimeException(e);
}finally{
try {
config.close();
}catch(Exception e){
e.printStackTrace();
}
}
}
private static Map<String,Mapper> loadMapperConfiguration(String mapperPath)throws IOException {
InputStream in = null;
try{
Map<String,Mapper> mappers = new HashMap<String,Mapper>();
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){
throw new RuntimeException(e);
}finally{
in.close();
}
}
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;
}
}
SqlSessionFactory工厂接口
- 生产 DefaultSqlSession对象,为了降低耦合度。
SqlSessionFactory.java
package cn.water.mybatis.session;
public interface SqlSessionFactory {
public abstract SqlSession openSession();
}
DefaultSqlSessionFactory工厂实现类
DefaultSqlSessionFactory.java
package cn.water.mybatis.defaults;
import cn.water.mybatis.cfg.Configuration;
import cn.water.mybatis.session.SqlSession;
import cn.water.mybatis.session.SqlSessionFactory;
public class DefaultSqlSessionFactory implements SqlSessionFactory {
private Configuration configuration;
public DefaultSqlSessionFactory(Configuration configuration) {
this.configuration = configuration;
}
public SqlSession openSession() {
return new DefaultSqlSession(configuration);
}
}
SqlSession产品接口
SqlSession.java
package cn.water.mybatis.session;
public interface SqlSession {
<T> T getMapper(Class<T> daoInterface);
void close();
}
DefaultSqlSession产品实现类
DefaultSqlSession.java
package cn.water.mybatis.defaults;
import cn.water.mybatis.Utils.DataSourceUtil;
import cn.water.mybatis.cfg.Configuration;
import cn.water.mybatis.proxy.MapperProxy;
import cn.water.mybatis.session.SqlSession;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.SQLException;
public class DefaultSqlSession implements SqlSession {
private Configuration configuration;
private Connection connection;
public DefaultSqlSession(Configuration configuration) {
this.configuration = configuration;
connection = DataSourceUtil.getConnection(configuration);
}
public <T> T getMapper(Class<T> daoInterface) {
return (T) Proxy.newProxyInstance(
daoInterface.getClassLoader(),
new Class[]{daoInterface},
new MapperProxy(configuration.getMappers(), connection));
}
public void close() {
if (connection!=null){
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
DataSourceUtils工具类
DataSourceUtils.java
package cn.water.mybatis.Utils;
import cn.water.mybatis.cfg.Configuration;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class DataSourceUtil {
public static Connection getConnection(Configuration configuration) {
try {
Class.forName(configuration.getDriver());
return DriverManager.getConnection(configuration.getUrl(),configuration.getUsername(),configuration.getUsername());
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
MapperProxy代理增强类
MapperProxy.java
package cn.water.mybatis.proxy;
import cn.water.mybatis.Utils.Executor;
import cn.water.mybatis.cfg.Mapper;
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);
}
}
Executor工具类
Executor.java
package cn.water.mybatis.Utils;
import cn.water.mybatis.cfg.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;
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) {
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();
}
}
}
}
执行结果
- 执行不同的测试类记得更换 MyBatis配置文件中的 mapper标签 和 测试类中代理对象的接口字节码。
xml
使用的是XML
User{id=41, username='老王', birthday=2018-02-27 17:47:08.0, sex='男', address='北京'}
User{id=42, username='小二王', birthday=2018-03-02 15:09:37.0, sex='女', address='北京金燕龙'}
User{id=43, username='小二王', birthday=2018-03-04 11:34:34.0, sex='女', address='北京金燕龙'}
User{id=45, username='传智播客', birthday=2018-03-04 12:04:06.0, sex='男', address='北京金燕龙'}
User{id=46, username='老王', birthday=2018-03-07 17:37:26.0, sex='男', address='北京'}
User{id=48, username='小马宝莉', birthday=2018-03-08 11:44:00.0, sex='女', address='北京修正'}
注解
使用的是注解
User{id=41, username='老王', birthday=2018-02-27 17:47:08.0, sex='男', address='北京'}
User{id=42, username='小二王', birthday=2018-03-02 15:09:37.0, sex='女', address='北京金燕龙'}
User{id=43, username='小二王', birthday=2018-03-04 11:34:34.0, sex='女', address='北京金燕龙'}
User{id=45, username='传智播客', birthday=2018-03-04 12:04:06.0, sex='男', address='北京金燕龙'}
User{id=46, username='老王', birthday=2018-03-07 17:37:26.0, sex='男', address='北京'}
User{id=48, username='小马宝莉', birthday=2018-03-08 11:44:00.0, sex='女', address='北京修正'}