Mybatis接口编程原理分析（三）

前面两篇博客Mybatis接口编程原理分析（一）和Mybatis接口编程原理分析（二）我们介绍了MapperProxyFactory、MapperProxy和MapperMethod的操作及源码分析，接下来我们介绍MapperRegistry

MapperRegistry：它是用来注册Mapper接口和获取登出代理类实例的工具类，它通过getMapper函数获得代理类和addMapper函数来注册代理类，

源码如下：

//这个类通过名字就可以看出 是用来注册Mapper接口与获取生成代理类实例的工具类public class MapperRegistry { //全局配置文件对象 private final Configuration config; //一个HashMap Key是mapper的类型对象, Value是MapperProxyFactory对象 //这个MapperProxyFactory是创建Mapper代理对象的工厂 private final Map<Class<?>, MapperProxyFactory<?>> knownMappers = new HashMap<Class<?>, MapperProxyFactory<?>>(); public MapperRegistry(Configuration config) { this.config = config; } //获取生成的代理对象 @SuppressWarnings("unchecked") public <T> T getMapper(Class<T> type, SqlSession sqlSession) {//通过Mapper的接口类型 去Map当中查找 如果为空就抛异常 final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type); if (mapperProxyFactory == null) { throw new BindingException("Type " + type + " is not known to the MapperRegistry."); } try { //否则创建一个当前接口的代理对象 并且传入sqlSession return mapperProxyFactory.newInstance(sqlSession); } catch (Exception e) { throw new BindingException("Error getting mapper instance. Cause: " + e, e); } } public <T> boolean hasMapper(Class<T> type) { return knownMappers.containsKey(type); } //注册Mapper接口 public <T> void addMapper(Class<T> type) { if (type.isInterface()) { if (hasMapper(type)) { throw new BindingException("Type " + type + " is already known to the MapperRegistry."); } boolean loadCompleted = false; try { knownMappers.put(type, new MapperProxyFactory<T>(type)); // It's important that the type is added before the parser is run // otherwise the binding may automatically be attempted by the // mapper parser. If the type is already known, it won't try. MapperAnnotationBuilder parser = new MapperAnnotationBuilder(config, type); parser.parse(); loadCompleted = true; } finally { if (!loadCompleted) { knownMappers.remove(type); } } } } /** * @since 3.2.2 */ public Collection<Class<?>> getMappers() { return Collections.unmodifiableCollection(knownMappers.keySet()); } /** * @since 3.2.2 */ //注册Mapper接口 public void addMappers(String packageName, Class<?> superType) { ResolverUtil<Class<?>> resolverUtil = new ResolverUtil<Class<?>>(); resolverUtil.find(new ResolverUtil.IsA(superType), packageName); Set<Class<? extends Class<?>>> mapperSet = resolverUtil.getClasses(); for (Class<?> mapperClass : mapperSet) { addMapper(mapperClass); } } /** * @since 3.2.2 */ //通过包名扫描下面所有接口 public void addMappers(String packageName) { addMappers(packageName, Object.class); }}

在DefaultSqlSession中通过getMapper函数从Configuration中获取代理类：

@Override public <T> T getMapper(Class<T> type) { return configuration.<T>getMapper(type, this); }

在Configuration类中通过getMapper从MapperRegistry来获取代理类

public <T> T getMapper(Class<T> type, SqlSession sqlSession) { return mapperRegistry.getMapper(type, sqlSession); }

这样就完成了mybatis接口编程的构造和调用的全部过程。