Mybaits源码分析九之sql执行流程

对应的源码为：

1   @Override
2   public <T> T getMapper(Class<T> type) {
3     return configuration.<T>getMapper(type, this);
4   }

1 public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
2     return mapperRegistry.getMapper(type, sqlSession);
3   }

 1 @SuppressWarnings("unchecked")
 2   public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
 3     //创建mapper代理工厂 type的值为UserDao接口类实例
 4     final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
 5     if (mapperProxyFactory == null) {
 6       throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
 7     }
 8     try {
 9      //返回Mapper的代理实例
10       return mapperProxyFactory.newInstance(sqlSession);
11     } catch (Exception e) {
12       throw new BindingException("Error getting mapper instance. Cause: " + e, e);
13     }
14   }

1 public T newInstance(SqlSession sqlSession) {
2     final MapperProxy<T> mapperProxy = new MapperProxy<T>(sqlSession, mapperInterface, methodCache);
3     //返回的MapperProxy实例
4     return newInstance(mapperProxy);
5   }

myBatis指明具体调用的接口

1  List<Subject> subjectList=subjectDao.selectSubject01();

其源码分析为因为之前返回的时mapper的类实例，调用具体方法会使用invoke方法即：

 1   @Override
 2   public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
 3     try {
 4       //判断这个类是否是方法类的class对象
 5       if (Object.class.equals(method.getDeclaringClass())) {
 6         return method.invoke(this, args);
 7       } else if (isDefaultMethod(method)) {
 8         //调用默认方法
 9         return invokeDefaultMethod(proxy, method, args);
10       }
11     } catch (Throwable t) {
12       throw ExceptionUtil.unwrapThrowable(t);
13     }
          //将方法加入到此方法
14     final MapperMethod mapperMethod = cachedMapperMethod(method);
          //调用执行器
15     return mapperMethod.execute(sqlSession, args);
16   }

此执行器会判断此接口是执行哪一种类型的sql，

 1 public Object execute(SqlSession sqlSession, Object[] args) {
 2     Object result;
 3     switch (command.getType()) {
 4       case INSERT: {
 5         Object param = method.convertArgsToSqlCommandParam(args);
 6         result = rowCountResult(sqlSession.insert(command.getName(), param));
 7         break;
 8       }
 9       case UPDATE: {
10         Object param = method.convertArgsToSqlCommandParam(args);
11         result = rowCountResult(sqlSession.update(command.getName(), param));
12         break;
13       }
14       case DELETE: {
15         Object param = method.convertArgsToSqlCommandParam(args);
16         result = rowCountResult(sqlSession.delete(command.getName(), param));
17         break;
18       }
19       case SELECT:
20         if (method.returnsVoid() && method.hasResultHandler()) {
21           executeWithResultHandler(sqlSession, args);
22           result = null;
23         } else if (method.returnsMany()) {
24           result = executeForMany(sqlSession, args);
25         } else if (method.returnsMap()) {
26           result = executeForMap(sqlSession, args);
27         } else if (method.returnsCursor()) {
28           result = executeForCursor(sqlSession, args);
29         } else {
30           Object param = method.convertArgsToSqlCommandParam(args);
31           result = sqlSession.selectOne(command.getName(), param);
32         }
33         break;
34       case FLUSH:
35         result = sqlSession.flushStatements();
36         break;
37       default:
38         throw new BindingException("Unknown execution method for: " + command.getName());
39     }
40     if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
41       throw new BindingException("Mapper method ‘" + command.getName() 
42           + " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
43     }
44     return result;
45   }

Mybaits源码分析九之sql执行流程

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