Mybaits源码分析九之sql执行流程

SubjectDao subjectDao=sqlSession.getMapper(SubjectDao. class );

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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