Package org.apache.cayenne.query

Class MappedSelect<T>

    • Field Detail

      • resultClass

        protected Class<T> resultClass

      • fetchLimit

        protected Integer fetchLimit

      • fetchOffset

        protected Integer fetchOffset

      • statementFetchSize

        protected Integer statementFetchSize

      • queryTimeout

        protected Integer queryTimeout

      • pageSize

        protected Integer pageSize

      • forceNoCache

        protected boolean forceNoCache

    • Constructor Detail

      • MappedSelect

        protected MappedSelect​(String queryName)

      • MappedSelect

        protected MappedSelect​(String queryName,
                       Class<T> resultClass)

    • Method Detail

      • query

        public static <T> MappedSelect<T> query​(String queryName,
                                        Class<T> rootClass)
        Loads query with the given name, which selects objects of a given persistent class, from the mapping configuration.
        Parameters:
        queryName - name of the mapped query
        rootClass - the Class of objects fetched by this query

      • query

        public static MappedSelect<?> query​(String queryName)
        Loads query with the given name from the mapping configuration.
        Parameters:
        queryName - name of the mapped query

      • limit

        public MappedSelect<T> limit​(int fetchLimit)
        Resets query fetch limit - a parameter that defines max number of objects that should be ever be fetched from the database.

      • offset

        public MappedSelect<T> offset​(int fetchOffset)
        Resets query fetch offset - a parameter that defines how many objects should be skipped when reading data from the database.

      • statementFetchSize

        public MappedSelect<T> statementFetchSize​(int statementFetchSize)
        Sets fetch size of the PreparedStatement generated for this query. Only non-negative values would change the default size.
        See Also:
        Statement.setFetchSize(int)

      • pageSize

        public MappedSelect<T> pageSize​(int pageSize)
        Resets query page size. A non-negative page size enables query result pagination that saves memory and processing time for large lists if only parts of the result are ever going to be accessed.

      • forceNoCache

        public MappedSelect<T> forceNoCache()
        Forces query cache to be refreshed during the execution of this query.

      • select

        public List<T> select​(ObjectContext context)
        Description copied from interface: Select
        Selects objects using provided context.

        Essentially the inversion of "ObjectContext.select(Select)".

        Specified by:
        select in interface Select<T>

      • selectOne

        public T selectOne​(ObjectContext context)
        Description copied from interface: Select
        Selects a single object using provided context. The query is expected to match zero or one object. It returns null if no objects were matched. If query matched more than one object, CayenneRuntimeException is thrown.

        Essentially the inversion of "ObjectContext.selectOne(Select)".

        Specified by:
        selectOne in interface Select<T>

      • selectFirst

        public T selectFirst​(ObjectContext context)
        Description copied from interface: Select
        Selects a single object using provided context. The query itself can match any number of objects, but will return only the first one. It returns null if no objects were matched.

        If it matched more than one object, the first object from the list is returned. This makes 'selectFirst' different from Select.selectOne(ObjectContext), which would throw in this situation. 'selectFirst' is useful e.g. when the query is ordered and we only want to see the first object (e.g. "most recent news article"), etc.

        Selecting the first object via "Select.selectFirst(ObjectContext)" is more comprehensible than selecting via "ObjectContext.selectFirst(Select)", because implementations of "Select" set fetch size limit to one.

        Specified by:
        selectFirst in interface Select<T>

      • iterate

        public void iterate​(ObjectContext context,
                    ResultIteratorCallback<T> callback)
        Description copied from interface: Select
        Creates a ResultIterator based on the provided context and passes it to a callback for processing. The caller does not need to worry about closing the iterator. This method takes care of it.

        Essentially the inversion of "ObjectContext.iterate(Select, ResultIteratorCallback)".

        Specified by:
        iterate in interface Select<T>

      • iterator

        public ResultIterator<T> iterator​(ObjectContext context)
        Description copied from interface: Select
        Creates a ResultIterator based on the provided context. It is usually backed by an open result set and is useful for processing of large data sets, preserving a constant memory footprint. The caller must wrap iteration in try/finally (or try-with-resources for Java 1.7 and higher) and close the ResultIterator explicitly. Or use Select.iterate(ObjectContext, ResultIteratorCallback) as an alternative.

        Essentially the inversion of "ObjectContext.iterator(Select)".

        Specified by:
        iterator in interface Select<T>

      • batchIterator

        public ResultBatchIterator<T> batchIterator​(ObjectContext context,
                                            int size)
        Description copied from interface: Select
        Creates a ResultBatchIterator based on the provided context and batch size. It is usually backed by an open result set and is useful for processing of large data sets, preserving a constant memory footprint. The caller must wrap iteration in try/finally (or try-with-resources for Java 1.7 and higher) and close the ResultBatchIterator explicitly.
        Specified by:
        batchIterator in interface Select<T>