自定义Mybatis框架实现
使用端（MybatisDemo）
我们这里使用端就使用MybatisDemo了，在使用端项目中的resource目录下创建核心配置文件sqlMapConfig.xml以及映射文件mapper.xml
PS：需要引入框架端（myMybatis）的依赖
MybatisDemo的pom文件
<dependency>
<groupId>com.hyq</groupId>
<artifactId>myMybatis</artifactId>
<version>1.0-SNAPSHOT</version>
</dependency>
sqlMapConfig.xml
<configuration>
<!--数据库连接信息-->
<property name="driverClass" value="com.mysql.jdbc.Driver"></property>
<property name="jdbcUrl" value="jdbc:mysql://xxx.xxx.xxx.xxx:3306/mytest?characterEncoding=utf-8&useSSL=false"></property>
<property name="user" value="root"></property>
<property name="password" value="123456"></property>
<!--引入sql配置信息-->
<mapper resource="mapper.xml"></mapper>
</configuration>
mapper.xml
<mapper namespace="user">
<select id="selectOne" paramterType="com.hyq.pojo.User" resultType="com.hyq.pojo.User">
select * from user where id = #{id} and username =#{username}
</select>
<select id="selectList" resultType="com.hyq.pojo.User">
select * from user
</select>
</mapper>
框架端（myMybatis）
新建module命名如下作为框架端使用
<groupId>com.hyq</groupId>
<artifactId>myMybatis</artifactId>
<version>1.0-SNAPSHOT</version>
添加依赖
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.17</version>
</dependency>
<dependency>
<groupId>c3p0</groupId>
<artifactId>c3p0</artifactId>
<version>0.9.1.2</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.12</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.10</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>
加载配置文件
根据配置文件的路径，加载配置文件成字节输入流，存储在内存中
创建Resources类，方法：InputStream getResourceAsStream(String path)
package com.hyq.io;
import java.io.InputStream;
public class Resources {
/*
根据配置文件的路径，将配置文件加载成字节输入流，存储在内存中
*/
public static InputStream getResourceAsStream(String path){
InputStream resourceAsStream = Resources.class.getClassLoader().getResourceAsStream(path);
return resourceAsStream;
}
}
测试Resources
记得在使用端的pom文件中添加框架端的依赖
创建两个JavaBean（容器对象）
加载进来的配置文件以流的形式存在，我们不能将读取到的配置信息以流的形式存放在内存中，不好操作，可以创建javaBean（容器对象）来存储
（1）Configuration : 核心配置类，存放sqlMapConfig.xml解析出来的内容
（2）MappedStatement：映射配置类，存放mapper.xml解析出来的内容
我们先创建MappedStatement类
package com.hyq.pojo;
public class MappedStatement {
//id标识
private String id;
//返回值类型
private String resultType;
//参数值类型
private String paramterType;
//sql语句
private String sql;
//省略了get set 方法，自己生成
}
Configuration
package com.hyq.pojo;
import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;
public class Configuration {
private DataSource dataSource;
/*
* key: statementid (namespace + id )
* value:封装好的mappedStatement对象
*/
private Map<String , MappedStatement> mappedStatementMap = new HashMap<>();
public DataSource getDataSource() {
return dataSource;
}
public void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
}
public Map<String, MappedStatement> getMappedStatementMap() {
return mappedStatementMap;
}
public void setMappedStatementMap(Map<String, MappedStatement> mappedStatementMap) {
this.mappedStatementMap = mappedStatementMap;
}
}
解析配置文件：dom4j
创建sqlSessionFactoryBuilder类，方法：sqlSessionFactory build(InputStream in)
- 使用dom4j解析配置文件，将解析出来的内容封装到Configuration和MappedStatement中
- 创建SqlSessionFactory的实现类DefaultSqlSession，生产sqlSession(会话对象) --工厂模式
开始之前需要提前准备一些工具类：
具体代码如下：
GenericTokenParser
/**
* Copyright 2009-2017 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hyq.utils;
/**
* @author Clinton Begin
*/
public class GenericTokenParser {
private final String openToken; //开始标记
private final String closeToken; //结束标记
private final TokenHandler handler; //标记处理器
public GenericTokenParser(String openToken, String closeToken, TokenHandler handler) {
this.openToken = openToken;
this.closeToken = closeToken;
this.handler = handler;
}
/**
* 解析${}和#{}
* @param text
* @return
* 该方法主要实现了配置文件、脚本等片段中占位符的解析、处理工作，并返回最终需要的数据。
* 其中，解析工作由该方法完成，处理工作是由处理器handler的handleToken()方法来实现
*/
public String parse(String text) {
// 验证参数问题，如果是null，就返回空字符串。
if (text == null || text.isEmpty()) {
return "";
}
// 下面继续验证是否包含开始标签，如果不包含，默认不是占位符，直接原样返回即可，否则继续执行。
int start = text.indexOf(openToken, 0);
if (start == -1) {
return text;
}
// 把text转成字符数组src，并且定义默认偏移量offset=0、存储最终需要返回字符串的变量builder，
// text变量中占位符对应的变量名expression。判断start是否大于-1(即text中是否存在openToken)，如果存在就执行下面代码
char[] src = text.toCharArray();
int offset = 0;
final StringBuilder builder = new StringBuilder();
StringBuilder expression = null;
while (start > -1) {
// 判断如果开始标记前如果有转义字符，就不作为openToken进行处理，否则继续处理
if (start > 0 && src[start - 1] == '\\') {
builder.append(src, offset, start - offset - 1).append(openToken);
offset = start + openToken.length();
} else {
//重置expression变量，避免空指针或者老数据干扰。
if (expression == null) {
expression = new StringBuilder();
} else {
expression.setLength(0);
}
builder.append(src, offset, start - offset);
offset = start + openToken.length();
int end = text.indexOf(closeToken, offset);
while (end > -1) {存在结束标记时
if (end > offset && src[end - 1] == '\\') {//如果结束标记前面有转义字符时
// this close token is escaped. remove the backslash and continue.
expression.append(src, offset, end - offset - 1).append(closeToken);
offset = end + closeToken.length();
end = text.indexOf(closeToken, offset);
} else {//不存在转义字符，即需要作为参数进行处理
expression.append(src, offset, end - offset);
offset = end + closeToken.length();
break;
}
}
if (end == -1) {
// close token was not found.
builder.append(src, start, src.length - start);
offset = src.length;
} else {
//首先根据参数的key（即expression）进行参数处理，返回?作为占位符
builder.append(handler.handleToken(expression.toString()));
offset = end + closeToken.length();
}
}
start = text.indexOf(openToken, offset);
}
if (offset < src.length) {
builder.append(src, offset, src.length - offset);
}
return builder.toString();
}
}
ParameterMapping
package com.hyq.utils;
public class ParameterMapping {
private String content;
public ParameterMapping(String content) {
this.content = content;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
}
ParameterMappingTokenHandler
package com.hyq.utils;
import java.util.ArrayList;
import java.util.List;
public class ParameterMappingTokenHandler implements TokenHandler {
private List<ParameterMapping> parameterMappings = new ArrayList<ParameterMapping>();
// context是参数名称 #{id} #{username}
public String handleToken(String content) {
parameterMappings.add(buildParameterMapping(content));
return "?";
}
private ParameterMapping buildParameterMapping(String content) {
ParameterMapping parameterMapping = new ParameterMapping(content);
return parameterMapping;
}
public List<ParameterMapping> getParameterMappings() {
return parameterMappings;
}
public void setParameterMappings(List<ParameterMapping> parameterMappings) {
this.parameterMappings = parameterMappings;
}
}
TokenHandler
/**
* Copyright 2009-2015 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hyq.utils;
/**
* @author Clinton Begin
*/
public interface TokenHandler {
String handleToken(String content);
}
好了开始干活~
使用dom4j解析配置文件，将解析出来的内容封装到Configuration和MappedStatement中
创建 XMLConfigBuilder 类，解析xml配置文件
XMLConfigBuilder
package com.hyq.config;
import com.hyq.io.Resources;
import com.hyq.pojo.Configuration;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import java.beans.PropertyVetoException;
import java.io.InputStream;
import java.util.List;
import java.util.Properties;
public class XMLConfigBuilder {
private Configuration configuration;
public XMLConfigBuilder() {
this.configuration = new Configuration();
}
/**
* 该方法就是使用dom4j对配置文件进行解析，封装Configuration
*/
public Configuration parseConfig(InputStream inputStream) throws DocumentException, PropertyVetoException {
Document document = new SAXReader().read(inputStream);
//<configuration>
Element rootElement = document.getRootElement();
List<Element> list = rootElement.selectNodes("//property");
Properties properties = new Properties();
for (Element element : list) {
String name = element.attributeValue("name");
String value = element.attributeValue("value");
properties.setProperty(name,value);
}
ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource();
comboPooledDataSource.setDriverClass(properties.getProperty("driverClass"));
comboPooledDataSource.setJdbcUrl(properties.getProperty("jdbcUrl"));
comboPooledDataSource.setUser(properties.getProperty("username"));
comboPooledDataSource.setPassword(properties.getProperty("password"));
configuration.setDataSource(comboPooledDataSource);
//mapper.xml解析: 拿到路径--字节输入流---dom4j进行解析
List<Element> mapperList = rootElement.selectNodes("//mapper");
for (Element element : mapperList) {
String mapperPath = element.attributeValue("resource");
InputStream resourceAsSteam = Resources.getResourceAsStream(mapperPath);
XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(configuration);
xmlMapperBuilder.parse(resourceAsSteam);
}
return configuration;
}
}
创建XMLMapperBuilder
package com.hyq.config;
import com.hyq.pojo.Configuration;
import com.hyq.pojo.MappedStatement;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import java.io.InputStream;
import java.util.List;
public class XMLMapperBuilder {
private Configuration configuration;
public XMLMapperBuilder(Configuration configuration) {
this.configuration =configuration;
}
public void parse(InputStream inputStream) throws DocumentException {
Document document = new SAXReader().read(inputStream);
Element rootElement = document.getRootElement();
String namespace = rootElement.attributeValue("namespace");
List<Element> list = rootElement.selectNodes("//select");
for (Element element : list) {
String id = element.attributeValue("id");
String resultType = element.attributeValue("resultType");
String paramterType = element.attributeValue("paramterType");
String sqlText = element.getTextTrim();
MappedStatement mappedStatement = new MappedStatement();
mappedStatement.setId(id);
mappedStatement.setResultType(resultType);
mappedStatement.setParamterType(paramterType);
mappedStatement.setSql(sqlText);
String key = namespace+"."+id;
configuration.getMappedStatementMap().put(key,mappedStatement);
}
}
}
创建SqlSessionFactory的实现类DefaultSqlSessionFactory，生产sqlSession(会话对象) --工厂模式
SqlSessionFactory
package com.hyq.sqlSession;
public interface SqlSessionFactory {
public SqlSession openSession();
}
DefaultSqlSessionFactory
package com.hyq.sqlSession;
import com.hyq.pojo.Configuration;
public class DefaultSqlSessionFactory implements SqlSessionFactory{
private Configuration configuration;
public DefaultSqlSessionFactory(Configuration configuration) {
this.configuration = configuration;
}
@Override
public SqlSession openSession() {
return new DefaultSqlSession(configuration);
}
}
创建sqlSession接口及实现类DefaultSqlSession
首先准备BoundSql
BoundSql
package com.hyq.config;
import com.hyq.utils.ParameterMapping;
import java.util.ArrayList;
import java.util.List;
public class BoundSql {
private String sqlText; //解析过后的sql
private List<ParameterMapping> parameterMappingList = new ArrayList<>();
public BoundSql(String sqlText, List<ParameterMapping> parameterMappingList) {
this.sqlText = sqlText;
this.parameterMappingList = parameterMappingList;
}
public String getSqlText() {
return sqlText;
}
public void setSqlText(String sqlText) {
this.sqlText = sqlText;
}
public List<ParameterMapping> getParameterMappingList() {
return parameterMappingList;
}
public void setParameterMappingList(List<ParameterMapping> parameterMappingList) {
this.parameterMappingList = parameterMappingList;
}
}
sqlSession
package com.hyq.sqlSession;
import java.util.List;
public interface SqlSession {
//查询所有
public <E> List<E> selectList(String statementid, Object... params) throws Exception;
//根据条件查询单个
public <T> T selectOne(String statementid,Object... params) throws Exception;
//为Dao接口生成代理实现类
public <T> T getMapper(Class<?> mapperClass);
}
DefaultSqlSession
package com.hyq.sqlSession;
import com.hyq.pojo.Configuration;
import com.hyq.pojo.MappedStatement;
import java.lang.reflect.*;
import java.util.List;
public class DefaultSqlSession implements SqlSession {
private Configuration configuration;
public DefaultSqlSession(Configuration configuration) {
this.configuration = configuration;
}
@Override
public <E> List<E> selectList(String statementid, Object... params) throws Exception {
//将要去完成对simpleExecutor里的query方法的调用
SimpleExecutor simpleExecutor = new SimpleExecutor();
MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);
return (List<E>) list;
}
@Override
public <T> T selectOne(String statementid, Object... params) throws Exception {
List<Object> objects = selectList(statementid, params);
if(objects.size()==1){
return (T) objects.get(0);
}else {
throw new RuntimeException("查询结果为空或者返回结果过多");
}
}
@Override
public <T> T getMapper(Class<?> mapperClass) {
// 使用JDK动态代理来为Dao接口生成代理对象，并返回
Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
// 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
// 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
// 方法名：findAll
String methodName = method.getName();
String className = method.getDeclaringClass().getName();
String statementId = className+"."+methodName;
// 准备参数2：params:args
// 获取被调用方法的返回值类型
Type genericReturnType = method.getGenericReturnType();
// 判断是否进行了 泛型类型参数化
if(genericReturnType instanceof ParameterizedType){
List<Object> objects = selectList(statementId, args);
return objects;
}
return selectOne(statementId,args);
}
});
return (T) proxyInstance;
}
}
创建Executor接口以及实现类SimpleExecutor实现类
Executor
package com.hyq.sqlSession;
import com.hyq.pojo.Configuration;
import com.hyq.pojo.MappedStatement;
import java.util.List;
public interface Executor {
public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception;
}
SimpleExecutor
package com.hyq.sqlSession;
import com.hyq.config.BoundSql;
import com.hyq.pojo.Configuration;
import com.hyq.pojo.MappedStatement;
import com.hyq.utils.GenericTokenParser;
import com.hyq.utils.ParameterMapping;
import com.hyq.utils.ParameterMappingTokenHandler;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
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 SimpleExecutor implements Executor{
@Override //user
public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
// 1. 注册驱动，获取连接
Connection connection = configuration.getDataSource().getConnection();
// 2. 获取sql语句 : select * from user where id = #{id} and username = #{username}
//转换sql语句： select * from user where id = ? and username = ? ，转换的过程中，还需要对#{}里面的值进行解析存储
String sql = mappedStatement.getSql();
BoundSql boundSql = getBoundSql(sql);
// 3.获取预处理对象：preparedStatement
PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
// 4. 设置参数
//获取到了参数的全路径
String paramterType = mappedStatement.getParamterType();
Class<?> paramtertypeClass = getClassType(paramterType);
List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
for (int i = 0; i < parameterMappingList.size(); i++) {
ParameterMapping parameterMapping = parameterMappingList.get(i);
String content = parameterMapping.getContent();
//反射
Field declaredField = paramtertypeClass.getDeclaredField(content);
//暴力访问
declaredField.setAccessible(true);
Object o = declaredField.get(params[0]);
preparedStatement.setObject(i+1,o);
}
// 5. 执行sql
ResultSet resultSet = preparedStatement.executeQuery();
String resultType = mappedStatement.getResultType();
Class<?> resultTypeClass = getClassType(resultType);
ArrayList<Object> objects = new ArrayList<>();
// 6. 封装返回结果集
while (resultSet.next()){
Object o =resultTypeClass.newInstance();
//元数据
ResultSetMetaData metaData = resultSet.getMetaData();
for (int i = 1; i <= metaData.getColumnCount(); i++) {
// 字段名
String columnName = metaData.getColumnName(i);
// 字段的值
Object value = resultSet.getObject(columnName);
//使用反射或者内省，根据数据库表和实体的对应关系，完成封装
PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
Method writeMethod = propertyDescriptor.getWriteMethod();
writeMethod.invoke(o,value);
}
objects.add(o);
}
return (List<E>) objects;
}
private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
if(paramterType!=null){
Class<?> aClass = Class.forName(paramterType);
return aClass;
}
return null;
}
/**
* 完成对#{}的解析工作：1.将#{}使用？进行代替，2.解析出#{}里面的值进行存储
* @param sql
* @return
*/
private BoundSql getBoundSql(String sql) {
//标记处理类：配置标记解析器来完成对占位符的解析处理工作
ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
//解析出来的sql
String parseSql = genericTokenParser.parse(sql);
//#{}里面解析出来的参数名称
List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
BoundSql boundSql = new BoundSql(parseSql,parameterMappings);
return boundSql;
}
}
测试
testSelect
@Test
public void testSelect() throws Exception {
InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
List<User> list = sqlSession.selectList("user.selectList");
System.out.println(list);
}