自定义持久层框架MyORMFramework—框架实现

Posted 2022-07-21 共饮一杯无

框架端

定义数据源配置和映射语句实体

Configuration

@Data
public class Configuration 

    private DataSource dataSource;

    /**
     *  key: statementId  value:封装好的mappedStatement对象
     */
    Map<String,MappedStatement> mappedStatementMap = new HashMap<>();

MappedStatement

@Data
public final class MappedStatement 

    private String id;
    /**
     * sql语句
     */
    private String sql;
    /**
     * 参数值类型
     */
    private Class<?> parameterType;
    /**
     * 返回值类型
     */
    private Class<?> resultType;

定义配置文件访问的工具类

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
     *
     * @param path
     * @return
     */
    public static InputStream getResourceAsSteam(String path) throws IOException 
        InputStream in = Resources.class.getClassLoader().getResourceAsStream(path);
        if (in == null) 
            throw new IOException("找不到资源" + path);
        
        return in;
    

定义SqlSessionFactoryBuilder

public class SqlSessionFactoryBuilder 

    private Configuration configuration;

    public SqlSessionFactoryBuilder() 
        this.configuration = new Configuration();
    

    public SqlSessionFactory build(InputStream inputStream) throws
            DocumentException, PropertyVetoException, ClassNotFoundException 
        //1.dom4j解析配置⽂件，封装Configuration
        XMLConfigerBuilder xmlConfigerBuilder = new
                XMLConfigerBuilder(configuration);
        Configuration configuration =
                xmlConfigerBuilder.parseConfiguration(inputStream);
        //2.创建SqlSessionFactory对象（工厂类），生产sqlSession:会话对象
        SqlSessionFactory sqlSessionFactory = new
                DefaultSqlSessionFactory(configuration);
        return sqlSessionFactory;
    

数据源配置和映射语句解析XMLConfigBuilder、XMLMapperBuilder

XMLConfigBuilder

public class XMLConfigerBuilder 

    private Configuration configuration;

    public XMLConfigerBuilder() 
        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, IOException, ClassNotFoundException 

        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);
        

        //连接池
        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.getResourceAsSteam(mapperPath);
            XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(configuration);
            xmlMapperBuilder.parse(resourceAsSteam);
        
        return configuration;
    

XMLMapperBuilder

public class XMLMapperBuilder 

    private Configuration configuration;

    public XMLMapperBuilder(Configuration configuration) 
        this.configuration = configuration;
    

    public void parse(InputStream inputStream) throws DocumentException,
            ClassNotFoundException 
        Document document = new SAXReader().read(inputStream);
        Element rootElement = document.getRootElement();
        String namespace = rootElement.attributeValue("namespace");
        List<Element> select = rootElement.selectNodes("select");
        for (Element element : select) 
            //id的值
            String id = element.attributeValue("id");
            String parameterType = element.attributeValue("parameterType");
            String resultType = element.attributeValue("resultType");
            //输⼊参数class
            Class<?> parameterTypeClass = getClassType(parameterType);
            //返回结果class
            Class<?> resultTypeClass = getClassType(resultType);
            //statementId
            String key = namespace + "." + id;
            //sql语句
            String textTrim = element.getTextTrim();
            //封装 mappedStatement
            MappedStatement mappedStatement = new MappedStatement();
            mappedStatement.setId(id);
            mappedStatement.setParameterType(parameterTypeClass);
            mappedStatement.setResultType(resultTypeClass);
            mappedStatement.setSql(textTrim);
            //填充 configuration
            configuration.getMappedStatementMap().put(key, mappedStatement);
        
    

    private Class<?> getClassType (String parameterType) throws
            ClassNotFoundException 
        Class<?> aClass = Class.forName(parameterType);
        return aClass;
    

SqlSessionFactory 接口及DefaultSqlSessionFactory 实现类

SqlSessionFactory

public interface SqlSessionFactory 
    SqlSession openSession();

DefaultSqlSessionFactory

public class DefaultSqlSessionFactory implements SqlSessionFactory 
    private Configuration configuration;

    public DefaultSqlSessionFactory(Configuration configuration) 
        this.configuration = configuration;
    

    @Override
    public SqlSession openSession() 
        return new DefaultSqlSession(configuration);
    

SqlSession 接口及 DefaultSqlSession 实现类

SqlSession

public interface SqlSession 

    /**
     * 查询所有
     *
     * @param statementId
     * @param params
     * @param <E>
     * @return
     * @throws Exception
     */
    <E> List<E> selectList(String statementId, Object... params) throws Exception;

    /**
     * 根据条件查询单个
     *
     * @param statementId
     * @param params
     * @param <T>
     * @return
     * @throws Exception
     */
    <T> T selectOne(String statementId, Object... params) throws Exception;

DefaultSqlSession

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");
        
    

SQL执行器接口和实现类Executor、SimpleExecutor

Executor

public interface Executor 
    /**
     * 执行查询SQL
     * @param configuration
     * @param mappedStatement
     * @param params
     * @param <E>
     * @return
     * @throws Exception
     */
    <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception;

SimpleExecutor

/**
 * SQL执行器实现
 *
 * @author zjq
 * @date 2022/3/15
 */
public class SimpleExecutor implements Executor 

    @Override
    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);
        Class<?> resultTypeClass = mappedStatement.getResultType();

        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,主要是配合通⽤标记解析器GenericTokenParser类完成对配置⽂件等的解析⼯作，其中TokenHandler主要完成处理
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        //GenericTokenParser :通⽤的标记解析器，完成了代码⽚段中的占位符的解析，然后再根据给定的标记处理器(TokenHandler)来进⾏表达式的处理
        //三个参数：分别为openToken (开始标记)、closeToken (结束标记)、handler (标记处理器)
        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;
    

使用端

创建 sqlMapConfig.xml

<configuration>

    <!--数据库配置信息-->
    <dataSource>
        <property name="driverClass" value="com.mysql.jdbc.Driver"></property>
        <property name="jdbcUrl" value="jdbc:mysql:///my-orm-framework"></property>
        <property name="username" value="root"></property>
        <property name="password" value="root"></property>
    </dataSource>

    <!--存放mapper.xml的全路径-->
    <mapper resource="UserMapper.xml"></mapper>

</configuration>

创建对应的mapper.xml

<mapper namespace="com.zjq.dao.IUserDao">

    <!--sql的唯一标识：namespace.id来组成 ： statementId-->
    <select id="findAll" resultType="com.zjq.pojo.User" >
        select * from user
    </select>

    <!--
        User user = new User()
        user.setId(1);
        user.setUsername("zhangsan")
    -->
    <select id="findByCondition" resultType="com.zjq.pojo.User" paramterType="com.zjq.pojo.User">
        select * from user where id = #id and username = #username
    </select>

</mapper>

UserDao

public interface IUserDao 

    //查询所有用户
    public List<User> findAll() throws Exception;

    //根据条件进行用户查询
    public User findByCondition(User user) throws Exception;

User实体

@Data
public class User 

    private Long id;

    private String username;

    private String password;

框架查询验证

    @Test
    public void test() throws Exception 
        InputStream resourceAsSteam = Resources.getResourceAsSteam("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsSteam);
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //调用
        User user = new User();
        user.setId(1);
        user.setUsername("张三");
        User user2 = sqlSession.selectOne("user.selectOne", user);

        System.out.println(user2);

        List<User> users = sqlSession.selectList("user.selectList");
        for (User user1 : users) 
          System.out.println(user1);