/*******************************************************************************
* Copyright 2013 SAP AG
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
******************************************************************************/
package com.sap.core.odata.processor.api.jpa.jpql;
import com.sap.core.odata.processor.api.jpa.exception.ODataJPAModelException;
import com.sap.core.odata.processor.api.jpa.exception.ODataJPARuntimeException;
import com.sap.core.odata.processor.api.jpa.factory.ODataJPAFactory;
/**
* The abstract class is a compilation of objects required for building
* {@link com.sap.core.odata.processor.api.jpa.jpql.JPQLStatement}. Extend this
* class to implement specific implementations of JPQL context types (Select,
* Join). A JPQL Context is constructed from an OData
* request. Depending on OData CRUD operation performed on an Entity, a
* corresponding JPQL context object is built. The JPQL context object thus
* built can be used for constructing JPQL statements. <br>
* A default implementation is provided by the library.
*
* @author SAP AG
* @see com.sap.core.odata.processor.api.jpa.jpql.JPQLStatement
* @see com.sap.core.odata.processor.api.jpa.jpql.JPQLContextType
* @see com.sap.core.odata.processor.api.jpa.factory.JPQLBuilderFactory
*
*/
public abstract class JPQLContext implements JPQLContextView {
/**
* An alias for Java Persistence Entity
*/
protected String jpaEntityAlias;
/**
* Java Persistence Entity name
*/
protected String jpaEntityName;
/**
* The type of JPQL context. Based on the type JPQL statements can be built.
*/
protected JPQLContextType type;
/**
* sets JPA Entity Name into the context
*
* @param jpaEntityName
* is the name of JPA Entity
*/
protected final void setJPAEntityName(final String jpaEntityName) {
this.jpaEntityName = jpaEntityName;
}
/**
* sets JPA Entity alias name into the context
*
* @param jpaEntityAlias
* is the JPA entity alias name
*/
protected final void setJPAEntityAlias(final String jpaEntityAlias) {
this.jpaEntityAlias = jpaEntityAlias;
}
/**
* gets the JPA entity alias name set into the context
*/
@Override
public final String getJPAEntityAlias() {
return jpaEntityAlias;
}
/**
* sets the JPQL context type into the context
*
* @param type
* is JPQLContextType
*/
protected final void setType(final JPQLContextType type) {
this.type = type;
}
/**
* gets the JPA entity name set into the context
*/
@Override
public final String getJPAEntityName() {
return jpaEntityName;
}
/**
* gets the JPQL context type set into the context
*/
@Override
public final JPQLContextType getType() {
return type;
}
/**
* the method returns an instance of type
* {@link com.sap.core.odata.processor.api.jpa.jpql.JPQLContext.JPQLContextBuilder}
* based on the JPQLContextType. The context builder can be used for
* building different JPQL contexts.
*
* @param contextType
* is the JPQLContextType
* @param resultsView
* is the OData request view
* @return an instance of type
* {@link com.sap.core.odata.processor.api.jpa.jpql.JPQLContext.JPQLContextBuilder}
* @throws ODataJPARuntimeException
*/
public final static JPQLContextBuilder createBuilder(
final JPQLContextType contextType, final Object resultsView)
throws ODataJPARuntimeException {
return JPQLContextBuilder.create(contextType, resultsView);
}
/**
* The abstract class is extended by specific JPQLContext builder for
* building JPQLContexts.
*
* @author SAP AG
*
*/
public static abstract class JPQLContextBuilder {
/**
* alias counter is an integer counter that is incremented by "1" for
* every new alias name generation. The value of counter is used in the
* generation of JPA entity alias names.
*/
protected int aliasCounter = 0;
protected JPQLContextBuilder() {}
/**
* the method instantiates an instance of type JPQLContextBuilder.
*
* @param contextType
* indicates the type of JPQLContextBuilder to instantiate.
* @param resultsView
* is the OData request view
* @return an instance of type
* {@link com.sap.core.odata.processor.api.jpa.jpql.JPQLContext.JPQLContextBuilder}
* @throws ODataJPARuntimeException
*/
private static JPQLContextBuilder create(final JPQLContextType contextType,
final Object resultsView) throws ODataJPARuntimeException {
JPQLContextBuilder contextBuilder = ODataJPAFactory.createFactory()
.getJPQLBuilderFactory().getContextBuilder(contextType);
if (contextBuilder == null) {
throw ODataJPARuntimeException
.throwException(
ODataJPARuntimeException.ERROR_JPQLCTXBLDR_CREATE,
null);
}
contextBuilder.setResultsView(resultsView);
return contextBuilder;
}
/**
* The abstract method is implemented by specific JPQL context builders
* to build JPQL Contexts. The build method makes use of information set
* into the context to built JPQL Context Types.
*
* @return an instance of
* {@link com.sap.core.odata.processor.api.jpa.jpql.JPQLContext}
* @throws ODataJPAModelException
* @throws ODataJPARuntimeException
*/
public abstract JPQLContext build() throws ODataJPAModelException,
ODataJPARuntimeException;
/**
* The abstract method is implemented by specific JPQL context builder.
* The method sets the OData request view into the JPQL context.
*
* @param resultsView
* is an instance representing OData request.
*/
protected abstract void setResultsView(Object resultsView);
/**
* The method resets the alias counter value to "0".
*/
protected void resetAliasCounter() {
aliasCounter = 0;
}
/**
* The method returns a system generated alias name starting with prefix
* "E" and ending with suffix "aliasCounter".
*
* @return a String representing JPA entity alias name
*/
protected String generateJPAEntityAlias() {
return new String("E" + ++aliasCounter);
}
}
}