liferay中 findxxxx 与fetchxxx 方法区别在于数据不存在时前者抛出异常后者返回Null
fetchByPrimaryKey
/**
* Returns the product with the primary key or returns <code>null</code> if it could not be found.
*
* @param productId the primary key of the product
* @return the product, or <code>null</code> if a product with the primary key could not be found
* @throws SystemException if a system exception occurred
*/
public Product fetchByPrimaryKey(long productId) throws SystemException
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findByPrimaryKey
/**
* Returns the product with the primary key or throws a {@link com.bluegrid.portlet.product.NoSuchProductException} if it could not be found.
*
* @param productId the primary key of the product
* @return the product
* @throws com.bluegrid.portlet.product.NoSuchProductException if a product with the primary key could not be found
* @throws SystemException if a system exception occurred
*/
public Product findByPrimaryKey(long productId)
throws NoSuchProductException, SystemException {