小傅哥，feat：《Mybatis 手撸专栏》第3章：实现映射器的注册和使用

mybatis-step-02/pom.xml

+<?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.bugstack.mybatis</groupId>
+    <artifactId>mybatis-step-02</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <dependencies>
+        <!-- https://mvnrepository.com/artifact/com.alibaba/fastjson -->
+        <dependency>
+            <groupId>com.alibaba</groupId>
+            <artifactId>fastjson</artifactId>
+            <version>1.2.75</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/org.dom4j/dom4j -->
+        <dependency>
+            <groupId>org.dom4j</groupId>
+            <artifactId>dom4j</artifactId>
+            <version>2.1.3</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/junit/junit -->
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.7</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>cn.hutool</groupId>
+            <artifactId>hutool-all</artifactId>
+            <version>5.5.0</version>
+        </dependency>
+        <!-- LOGGING begin -->
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-api</artifactId>
+            <version>1.7.5</version>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>jcl-over-slf4j</artifactId>
+            <version>1.7.5</version>
+        </dependency>
+        <dependency>
+            <groupId>ch.qos.logback</groupId>
+            <artifactId>logback-classic</artifactId>
+            <version>1.0.9</version>
+            <exclusions>
+                <exclusion>
+                    <artifactId>slf4j-api</artifactId>
+                    <groupId>org.slf4j</groupId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+        <!-- LOGGING end -->
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <compilerVersion>1.8</compilerVersion>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

mybatis-step-02/src/main/java/cn/bugstack/mybatis/binding/MapperProxy.java

+package cn.bugstack.mybatis.binding;
+
+import cn.bugstack.mybatis.session.SqlSession;
+
+import java.io.Serializable;
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+import java.util.Map;
+
+/**
+ * @author 小傅哥，微信：fustack
+ * @description 映射器代理类
+ * @date 2022/3/26
+ * @github https://github.com/fuzhengwei
+ * @Copyright 公众号：bugstack虫洞栈 | 博客：https://bugstack.cn - 沉淀、分享、成长，让自己和他人都能有所收获！
+ */
+public class MapperProxy<T> implements InvocationHandler, Serializable {
+
+    private static final long serialVersionUID = -6424540398559729838L;
+
+    private SqlSession sqlSession;
+    private final Class<T> mapperInterface;
+
+    public MapperProxy(SqlSession sqlSession, Class<T> mapperInterface) {
+        this.sqlSession = sqlSession;
+        this.mapperInterface = mapperInterface;
+    }
+
+    @Override
+    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+        if (Object.class.equals(method.getDeclaringClass())) {
+            return method.invoke(this, args);
+        } else {
+            return sqlSession.selectOne(method.getName(), args);
+        }
+    }
+
+}

mybatis-step-02/src/main/java/cn/bugstack/mybatis/binding/MapperProxyFactory.java

+package cn.bugstack.mybatis.binding;
+
+import cn.bugstack.mybatis.session.SqlSession;
+
+import java.lang.reflect.Proxy;
+
+/**
+ * @author 小傅哥，微信：fustack
+ * @description 映射器代理工厂
+ * @date 2022/3/26
+ * @github https://github.com/fuzhengwei/CodeDesignTutorials
+ * @Copyright 公众号：bugstack虫洞栈 | 博客：https://bugstack.cn - 沉淀、分享、成长，让自己和他人都能有所收获！
+ */
+public class MapperProxyFactory<T> {
+
+    private final Class<T> mapperInterface;
+
+    public MapperProxyFactory(Class<T> mapperInterface) {
+        this.mapperInterface = mapperInterface;
+    }
+
+    @SuppressWarnings("unchecked")
+    public T newInstance(SqlSession sqlSession) {
+        final MapperProxy<T> mapperProxy = new MapperProxy<>(sqlSession, mapperInterface);
+        return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[]{mapperInterface}, mapperProxy);
+    }
+
+}

mybatis-step-02/src/main/java/cn/bugstack/mybatis/binding/MapperRegistry.java

+package cn.bugstack.mybatis.binding;
+
+import cn.bugstack.mybatis.session.SqlSession;
+import cn.hutool.core.lang.ClassScanner;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * @author 小傅哥，微信：fustack
+ * @description 映射器注册机
+ * @date 2022/04/01
+ * @github https://github.com/fuzhengwei
+ * @copyright 公众号：bugstack虫洞栈 | 博客：https://bugstack.cn - 沉淀、分享、成长，让自己和他人都能有所收获！
+ */
+public class MapperRegistry {
+
+    /**
+     * 将已添加的映射器代理加入到 HashMap
+     */
+    private final Map<Class<?>, MapperProxyFactory<?>> knownMappers = new HashMap<>();
+
+    public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
+        final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
+        if (mapperProxyFactory == null) {
+            throw new RuntimeException("Type " + type + " is not known to the MapperRegistry.");
+        }
+        try {
+            return mapperProxyFactory.newInstance(sqlSession);
+        } catch (Exception e) {
+            throw new RuntimeException("Error getting mapper instance. Cause: " + e, e);
+        }
+    }
+
+    public <T> void addMapper(Class<T> type) {
+        /* Mapper 必须是接口才会注册 */
+        if (type.isInterface()) {
+            if (hasMapper(type)) {
+                // 如果重复添加了，报错
+                throw new RuntimeException("Type " + type + " is already known to the MapperRegistry.");
+            }
+            // 注册映射器代理工厂
+            knownMappers.put(type, new MapperProxyFactory<>(type));
+        }
+    }
+
+    public <T> boolean hasMapper(Class<T> type) {
+        return knownMappers.containsKey(type);
+    }
+
+    public void addMappers(String packageName) {
+        Set<Class<?>> mapperSet = ClassScanner.scanPackage(packageName);
+        for (Class<?> mapperClass : mapperSet) {
+            addMapper(mapperClass);
+        }
+    }
+
+}

mybatis-step-02/src/main/java/cn/bugstack/mybatis/session/SqlSession.java

+package cn.bugstack.mybatis.session;
+
+/**
+ * @author 小傅哥，微信：fustack
+ * @description SqlSession 用来执行SQL，获取映射器，管理事务。
+ * PS：通常情况下，我们在应用程序中使用的Mybatis的API就是这个接口定义的方法。
+ * @date 2022/04/01
+ * @github https://github.com/fuzhengwei
+ * @copyright 公众号：bugstack虫洞栈 | 博客：https://bugstack.cn - 沉淀、分享、成长，让自己和他人都能有所收获！
+ */
+public interface SqlSession {
+
+    /**
+     * Retrieve a single row mapped from the statement key
+     * 根据指定的SqlID获取一条记录的封装对象
+     *
+     * @param <T>       the returned object type 封装之后的对象类型
+     * @param statement sqlID
+     * @return Mapped object 封装之后的对象
+     */
+    <T> T selectOne(String statement);
+
+    /**
+     * Retrieve a single row mapped from the statement key and parameter.
+     * 根据指定的SqlID获取一条记录的封装对象，只不过这个方法容许我们可以给sql传递一些参数
+     * 一般在实际使用中，这个参数传递的是pojo，或者Map或者ImmutableMap
+     *
+     * @param <T>       the returned object type
+     * @param statement Unique identifier matching the statement to use.
+     * @param parameter A parameter object to pass to the statement.
+     * @return Mapped object
+     */
+    <T> T selectOne(String statement, Object parameter);
+
+    /**
+     * Retrieves a mapper.
+     * 得到映射器，这个巧妙的使用了泛型，使得类型安全
+     *
+     * @param <T>  the mapper type
+     * @param type Mapper interface class
+     * @return a mapper bound to this SqlSession
+     */
+    <T> T getMapper(Class<T> type);
+
+}

mybatis-step-02/src/main/java/cn/bugstack/mybatis/session/SqlSessionFactory.java

+package cn.bugstack.mybatis.session;
+
+/**
+ * @author 小傅哥，微信：fustack
+ * @description 工厂模式接口，构建SqlSession的工厂
+ * @date 2022/04/01
+ * @github https://github.com/fuzhengwei
+ * @copyright 公众号：bugstack虫洞栈 | 博客：https://bugstack.cn - 沉淀、分享、成长，让自己和他人都能有所收获！
+ */
+public interface SqlSessionFactory {
+
+    /**
+     * 打开一个 session
+     * @return SqlSession
+     */
+   SqlSession openSession();
+
+}

mybatis-step-02/src/main/java/cn/bugstack/mybatis/session/defaults/DefaultSqlSession.java

+package cn.bugstack.mybatis.session.defaults;
+
+import cn.bugstack.mybatis.binding.MapperRegistry;
+import cn.bugstack.mybatis.session.SqlSession;
+
+/**
+ * @author 小傅哥，微信：fustack
+ * @description 默认SqlSession实现类
+ * @date 2022/04/01
+ * @github https://github.com/fuzhengwei
+ * @copyright 公众号：bugstack虫洞栈 | 博客：https://bugstack.cn - 沉淀、分享、成长，让自己和他人都能有所收获！
+ */
+public class DefaultSqlSession implements SqlSession {
+
+    /**
+     * 映射器注册机
+     */
+    private MapperRegistry mapperRegistry;
+
+    public DefaultSqlSession(MapperRegistry mapperRegistry) {
+        this.mapperRegistry = mapperRegistry;
+    }
+
+    @Override
+    public <T> T selectOne(String statement) {
+        return (T) ("你被代理了！" + statement);
+    }
+
+    @Override
+    public <T> T selectOne(String statement, Object parameter) {
+        return (T) ("你被代理了！" + "方法：" + statement + " 入参：" + parameter);
+    }
+
+    @Override
+    public <T> T getMapper(Class<T> type) {
+        return mapperRegistry.getMapper(type, this);
+    }
+
+}

mybatis-step-02/src/main/java/cn/bugstack/mybatis/session/defaults/DefaultSqlSessionFactory.java

+package cn.bugstack.mybatis.session.defaults;
+
+import cn.bugstack.mybatis.binding.MapperRegistry;
+import cn.bugstack.mybatis.session.SqlSession;
+import cn.bugstack.mybatis.session.SqlSessionFactory;
+
+/**
+ * @author 小傅哥，微信：fustack
+ * @description 默认的 DefaultSqlSessionFactory
+ * @date 2022/04/01
+ * @github https://github.com/fuzhengwei
+ * @copyright 公众号：bugstack虫洞栈 | 博客：https://bugstack.cn - 沉淀、分享、成长，让自己和他人都能有所收获！
+ */
+public class DefaultSqlSessionFactory implements SqlSessionFactory {
+
+    private final MapperRegistry mapperRegistry;
+
+    public DefaultSqlSessionFactory(MapperRegistry mapperRegistry) {
+        this.mapperRegistry = mapperRegistry;
+    }
+
+    @Override
+    public SqlSession openSession() {
+        return new DefaultSqlSession(mapperRegistry);
+    }
+
+}

mybatis-step-02/src/test/java/cn/bugstack/mybatis/test/ApiTest.java

+package cn.bugstack.mybatis.test;
+
+import cn.bugstack.mybatis.binding.MapperRegistry;
+import cn.bugstack.mybatis.session.SqlSession;
+import cn.bugstack.mybatis.session.SqlSessionFactory;
+import cn.bugstack.mybatis.session.defaults.DefaultSqlSessionFactory;
+import cn.bugstack.mybatis.test.dao.IUserDao;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * @author 小傅哥，微信：fustack
+ * @description 单元测试
+ * @date 2022/3/26
+ * @github https://github.com/fuzhengwei
+ * @Copyright 公众号：bugstack虫洞栈 | 博客：https://bugstack.cn - 沉淀、分享、成长，让自己和他人都能有所收获！
+ */
+public class ApiTest {
+
+    private Logger logger = LoggerFactory.getLogger(ApiTest.class);
+
+    @Test
+    public void test_MapperProxyFactory() {
+        // 1. 注册 Mapper
+        MapperRegistry registry = new MapperRegistry();
+        registry.addMappers("cn.bugstack.mybatis.test.dao");
+
+        // 2. 从 SqlSession 工厂获取 Session
+        SqlSessionFactory sqlSessionFactory = new DefaultSqlSessionFactory(registry);
+        SqlSession sqlSession = sqlSessionFactory.openSession();
+
+        // 3. 获取映射器对象
+        IUserDao userDao = sqlSession.getMapper(IUserDao.class);
+
+        // 4. 测试验证
+        String res = userDao.queryUserName("10001");
+        logger.info("测试结果：{}", res);
+    }
+
+}

mybatis-step-02/src/test/java/cn/bugstack/mybatis/test/dao/ISchoolDao.java

+package cn.bugstack.mybatis.test.dao;
+
+public interface ISchoolDao {
+
+    String querySchoolName(String uId);
+
+}

mybatis-step-02/src/test/java/cn/bugstack/mybatis/test/dao/IUserDao.java

+package cn.bugstack.mybatis.test.dao;
+
+public interface IUserDao {
+
+    String queryUserName(String uId);
+
+    Integer queryUserAge(String uId);
+
+}