Mybatis mapper动态代理的原理解析_Mysql_

 public interface UserDao { /* 查询所有用户信息 */ List findAll(); /** * 保存用户 * @param user */ void save(User user); /** * 更新用户 * @return */ void update(User user); /** * 删除用户 */ void delete(Integer userId); /** * 查找一个用户 * @param userId * @return */ User findOne(Integer userId); /** * 根据名字模糊查询 * @param name * @return */ List findByName(String name); /** * 根据组合对象进行模糊查询 * @param vo * @return */ List findByQueryVo(QueryVo vo); }

 public class UserDaoImpl implements UserDao{ private SqlSessionFactory factory; public UserDaoImpl(SqlSessionFactory factory){ this.factory = factory; } public List findAll() { //1.获取sqlSession对象 SqlSession sqlSession = factory.openSession(); //2.调用selectList方法 List list = sqlSession.selectList("com.example.dao.UserDao.findAll"); //3.关闭流 sqlSession.close(); return list; } public void save(User user) { } public void update(User user) { } public void delete(Integer userId) { } public User findOne(Integer userId) { return null; } public List findByName(String name) { return null; } public List findByQueryVo(QueryVo vo) { return null; }

 //3.获取SqlSession对象 SqlSession session = factory.openSession(); //4.获取dao的代理对象 UserDao mapper = session.getMapper(UserDao.class); //5.执行查询所有的方法 List list = mapper.findAll();

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

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

 public  T getMapper(Class type, SqlSession sqlSession) { final MapperProxyFactory mapperProxyFactory = (MapperProxyFactory) knownMappers.get(type); if (mapperProxyFactory == null) { throw new BindingException("Type " + type + " is not known to the MapperRegistry."); } try { return mapperProxyFactory.newInstance(sqlSession); } catch (Exception e) { throw new BindingException("Error getting mapper instance. Cause: " + e, e); } }

 protected T newInstance(MapperProxy mapperProxy) { return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy); } public T newInstance(SqlSession sqlSession) { final MapperProxy mapperProxy = new MapperProxy(sqlSession, mapperInterface, methodCache); return newInstance(mapperProxy); }

 public class MapperProxy implements InvocationHandler, Serializable { private static final long serialVersionUID = -6424540398559729838L; private final SqlSession sqlSession; private final Class mapperInterface; private final Map methodCache; public MapperProxy(SqlSession sqlSession, Class mapperInterface, Map methodCache) { this.sqlSession = sqlSession; this.mapperInterface = mapperInterface; this.methodCache = methodCache; } @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { try { if (Object.class.equals(method.getDeclaringClass())) { return method.invoke(this, args); } else if (isDefaultMethod(method)) { return invokeDefaultMethod(proxy, method, args); } } catch (Throwable t) { throw ExceptionUtil.unwrapThrowable(t); } final MapperMethod mapperMethod = cachedMapperMethod(method); return mapperMethod.execute(sqlSession, args); } private MapperMethod cachedMapperMethod(Method method) { MapperMethod mapperMethod = methodCache.get(method); if (mapperMethod == null) { mapperMethod = new MapperMethod(mapperInterface, method, sqlSession.getConfiguration()); methodCache.put(method, mapperMethod); } return mapperMethod; } @UsesJava7 private Object invokeDefaultMethod(Object proxy, Method method, Object[] args) throws Throwable { final Constructor constructor = MethodHandles.Lookup.class .getDeclaredConstructor(Class.class, int.class); if (!constructor.isAccessible()) { constructor.setAccessible(true); } final Class declaringClass = method.getDeclaringClass(); return constructor .newInstance(declaringClass, MethodHandles.Lookup.PRIVATE | MethodHandles.Lookup.PROTECTED | MethodHandles.Lookup.PACKAGE | MethodHandles.Lookup.PUBLIC) .unreflectSpecial(method, declaringClass).bindTo(proxy).invokeWithArguments(args); } /** * Backport of java.lang.reflect.Method#isDefault() */ private boolean isDefaultMethod(Method method) { return ((method.getModifiers() & (Modifier.ABSTRACT | Modifier.PUBLIC | Modifier.STATIC)) == Modifier.PUBLIC) && method.getDeclaringClass().isInterface(); } }

 public Object execute(SqlSession sqlSession, Object[] args) { Object result; switch (command.getType()) { case INSERT: { Object param = method.convertArgsToSqlCommandParam(args); result = rowCountResult(sqlSession.insert(command.getName(), param)); break; } case UPDATE: { Object param = method.convertArgsToSqlCommandParam(args); result = rowCountResult(sqlSession.update(command.getName(), param)); break; } case DELETE: { Object param = method.convertArgsToSqlCommandParam(args); result = rowCountResult(sqlSession.delete(command.getName(), param)); break; } case SELECT: if (method.returnsVoid() && method.hasResultHandler()) { executeWithResultHandler(sqlSession, args); result = null; } else if (method.returnsMany()) { result = executeForMany(sqlSession, args); } else if (method.returnsMap()) { result = executeForMap(sqlSession, args); } else if (method.returnsCursor()) { result = executeForCursor(sqlSession, args); } else { Object param = method.convertArgsToSqlCommandParam(args); result = sqlSession.selectOne(command.getName(), param); } break; case FLUSH: result = sqlSession.flushStatements(); break; default: throw new BindingException("Unknown execution method for: " + command.getName()); } if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) { throw new BindingException("Mapper method '" + command.getName() + " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ")."); } return result; }

 public class MapperMethod { private final SqlCommand command; private final MethodSignature method; public MapperMethod(Class mapperInterface, Method method, Configuration config) { this.command = new SqlCommand(config, mapperInterface, method); this.method = new MethodSignature(config, mapperInterface, method); } public Object execute(SqlSession sqlSession, Object[] args) { Object result; switch (command.getType()) { case INSERT: { Object param = method.convertArgsToSqlCommandParam(args); result = rowCountResult(sqlSession.insert(command.getName(), param)); break; } case UPDATE: { Object param = method.convertArgsToSqlCommandParam(args); result = rowCountResult(sqlSession.update(command.getName(), param)); break; } case DELETE: { Object param = method.convertArgsToSqlCommandParam(args); result = rowCountResult(sqlSession.delete(command.getName(), param)); break; } case SELECT: if (method.returnsVoid() && method.hasResultHandler()) 
                
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