二、自定义MyBatis，手写源码
通过将mybatis依赖删除来手动实现功能
(同时涵盖了注解和xml配置的自定义mybatis）
pom.xml依赖
<dependencies>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>5.1.47version>
dependency>
<dependency>
<groupId>log4jgroupId>
<artifactId>log4jartifactId>
<version>1.2.17version>
dependency>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.13version>
<scope>testscope>
dependency>
<dependency>
<groupId>dom4jgroupId>
<artifactId>dom4jartifactId>
<version>1.6.1version>
dependency>
<dependency>
<groupId>jaxengroupId>
<artifactId>jaxenartifactId>
<version>1.1.6version>
dependency>
dependencies>
其中，分别为
public class Resources
public class SqlSessionFactoryBuilder
public interface SqlSessionFactory
public interface SqlSession
目录结构
1、创建Resources类
public class Resources {
public static InputStream getResourceAsStream(String filePath) {
return Resources.class.getClassLoader().getResourceAsStream(filePath);
}
}
2、创建SqlSessionFactoryBuilder类
public class SqlSessionFactoryBuilder {
private Configuration cfg;
public SqlSessionFactoryBuilder(Configuration cfg) {
this.cfg = cfg;
}
public SqlSessionFactoryBuilder() {
}
/**
* 根据参数的字节输入流来构建一个SqlSessionFactory工厂
* @param config
* @return
*/
public SqlSessionFactory build(InputStream config){
Configuration cfg = XMLConfigBuilder.loadConfiguration(config);
return new DefaultSqlSessionFactory(cfg);
}
}
3、创建SqlSessionFactory接口
public interface SqlSessionFactory {
SqlSession openSession();
}
4、创建SqlSession接口
public interface SqlSession {
<T> T getMapper(Class<T> doInterfaceClass);
void close();
}
5、创建工具类XMLConfigBuilder
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/lp/dao/UserDao.xml"
//把映射配置文件的内容获取出来，封装成一个map
Map<String,Mapper> mappers = loadMapperConfiguration(mapperPath);
//给configuration中的mappers赋值
System.out.println(mappers.entrySet());
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Configuration
return 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Key
String key = namespace+"."+id;
//创建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();//List6、工具类中需要Configuration，创建Configuration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) {
System.out.println(mappers.entrySet());
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;
}
}
7、工具类中需要Mapper，创建Mapper类
public class Mapper {
//sql
private String queryString;
//实体类的全限定类名
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;
}
}
8、DefaultSqlSession是SqlSession的实现类
/**
* SqlSession接口的实现类
*/
public class DefaultSqlSession implements SqlSession {
private Configuration cfg;
private Connection connection;
public DefaultSqlSession(Configuration cfg){
this.cfg = cfg;
connection = DataSourceUtil.getConnection(cfg);
}
public <T> T getMapper(Class<T> doInterfaceClass) {
return(T) Proxy.newProxyInstance(doInterfaceClass.getClassLoader(),
new Class[]{doInterfaceClass},new MapperProxy(cfg.getMappers(),connection));
}
public void close() {
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
9、DefaultSqlSessionFactory是SqlSessionFactory的实现类
/**
* SqlSessionFactory接口的实现类
*/
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
*/
public SqlSession openSession() {
return new DefaultSqlSession(cfg);
}
}
10、在DefaultSqlSession中需要通过反射获取全限定类名，需要用到MapperProxy类
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，其实就是调用selectList方法
*
* @param proxy
* @param method
* @param args
* @return
* @throws Throwable
*/
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
//获取方法名
String methodName = method.getName();
//获取方法所在类名称
String className = method.getDeclaringClass().getName();
//组合key
String key = className + "." + methodName;
System.out.println(key);
//获取mapper中的Mapper对象
Mapper mapper = mappers.get(key);
//判断是否有mapper
if (mapper == null) {
throw new IllegalArgumentException("传入参数有误！");
}
//调用工具类查询所有
return new Executor().selectList(mapper, conn);
}
}
11、我们需要DataSourceUtil工具类来获取数据源
/**
* 创建数据源的工具类
*/
public class DataSourceUtil {
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;
}
}
12、Executor类来负责执行SQL语句，并且封装结果集
/**
* @author lp
* 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 user
String resultType = mapper.getResultType();//com.lp.domain.User
Class 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：ResultSetMetaData
ResultSetMetaData 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();
}
}
}
}
13、利用注解操作时，我们需要Select
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Select {
String value();
}
14、测试类
public class test {
public static void main(String[] args) throws IOException {
//读取配置文件
InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
//创建SqlSessionFactory工厂
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
SqlSessionFactory sessionFactory = builder.build(inputStream);
//使用工厂生成SqlSession对象
SqlSession session = sessionFactory.openSession();
//使用SqlSession创建Dao接口的代理对象
UserDao userDao = session.getMapper(UserDao.class);
//使用代理对象执行方法
for (User user : userDao.getAll()) {
System.out.println(user);
}
// 释放资源
session.close();
inputStream.close();
}
}
15、mybatis配置文件SqlMapConfig.xml
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<!-- 配置环境-->
<environments default="mysql">
<!-- 配置mysql的环境-->
<environment id="mysql">
<!-- 配置事务的类型-->
<transactionManager type="JDBC"></transactionManager>
<!-- 配置数据源（连接池）-->
<dataSource type="POOLED">
<!-- 配置连接数据库的四个基本信息-->
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql:///eesy"/>
<property name="username" value="root"/>
<property name="password" value="密码"/>
</dataSource>
</environment>
</environments>
<!-- 指定映射配置文件，映射配置文件指的是每个dao独立的配置文件-->
<mappers>
<!-- <mapper resource="com/lp/dao/UserDao.xml"/>-->
<mapper class="com.lp.dao.UserDao"/>
</mappers>
</configuration>
16、log4j.properties配置文件
# Set root category priority to INFO and its only appender to CONSOLE.
#log4j.rootCategory=INFO, CONSOLE debug info warn error fatal
log4j.rootCategory=debug, CONSOLE, LOGFILE
# Set the enterprise logger category to FATAL and its only appender to CONSOLE.
log4j.logger.org.apache.axis.enterprise=FATAL, CONSOLE
# CONSOLE is set to be a ConsoleAppender using a PatternLayout.
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n
# LOGFILE is set to be a File appender using a PatternLayout.
log4j.appender.LOGFILE=org.apache.log4j.FileAppender
log4j.appender.LOGFILE.File=d:\axis.log
log4j.appender.LOGFILE.Append=true
log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.LOGFILE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n
17、映射文件UserDao.xml
<mapper namespace="com.lp.dao.UserDao">
<select id="getAll" resultType="com.lp.domain.User">
select * from user;
select>
mapper>
18、UserDao接口
public interface UserDao {
/**
* 查询所有
* @return
*/
@Select("select * from user")
List<User> getAll();
}
19、User实体类
public class User implements Serializable {
private Integer id;
private String username;
private Date birthday;
private String sex;
private String address;
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", birthday=" + birthday +
", sex='" + sex + '\'' +
", address='" + 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;
}
public User(Integer id, String username, Date birthday, String sex, String address) {
this.id = id;
this.username = username;
this.birthday = birthday;
this.sex = sex;
this.address = address;
}
public User() {
}
}