/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.openjpa.persistence.jest;
import java.io.IOException;
import java.util.Map;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
/**
* Interface for JEST commands. A JEST command denotes a JPA operation such as <code>find</code>,
* <code>query</code> or <code>domain</code>. Besides signifying a JPA operation, a command may have
* zero or more qualifiers and arguments.
* <br>
* A qualifier qualifies the action to be performed. For example, a <code>query</code> command may be qualified
* to return a single instance as its result, or limit its result to first 20 instances etc.
* <br>
* An argument is an argument to the target JPA method. For example, <code>find</code> command has
* arguments for the type of the instance and the primary key. A <code>query</code> command has the
* query string as its argument.
* <p>
* A concrete command instance is an outcome of parsing a {@link HttpServletRequest request}.
* The {@link HttpServletRequest#getPathInfo() path} segments are parsed for qualifiers.
* The {@link HttpServletRequest#getQueryString() query string} is parsed for the arguments.
* <p>
* A JEST command often attaches special semantics to a standard URI syntax. For example, all JEST
* URI enforces that the first segment of a servlet path denotes the command moniker e.g. the URI<br>
* <code>http://www.jpa.com/jest/find/plan=myPlan?type=Person&1234</code><br>
* with context root <code>http://www.jpa.com/jest</code> has the servlet path <code>/find/plan=myPlan</code>
* and query string <code>type=Person&1234</code>.
* <br>
* The first path segment <code>find</code> will determine that the command is to <em>find</em> a
* persistent entity of type <code>Person</code> and primary key <code>1234</code> using a fetch plan
* named <code>myPlan</code>.
*
* @author Pinaki Poddar
*
*/
public interface JESTCommand {
/**
* Supported format monikers.
*/
public static enum Format {xml, json};
/**
* Get the execution context of this command.
*
* @return the execution context. never null.
*/
public JPAServletContext getExecutionContext();
/**
* Parse the given request to populate qualifiers and parameters of this command.
* A command can interpret and consume certain path segments or parameters of the
* original request. During {@link #process(ServletRequest, ServletResponse, JPAServletContext) processing}
* phase, the parameters and qualifiers are accessed from the parsed command itself rather than
* from the original HTTP request.
*/
public void parse() throws ProcessingException;
/**
* Process the given request and write the output on to the given response in the given context.
* @throws ProcessingException
*
*/
public void process() throws ProcessingException, IOException;
/**
* Get this command's arguments.
*
* @exception IllegalStateException if accessed prior to parsing.
*/
public Map<String,String> getArguments();
/**
* Get the value of this command's argument of the given name.
*
* @return null if the argument does not exist.
*
* @exception IllegalStateException if accessed prior to parsing.
*/
public String getArgument(String key);
/**
* Affirm this command contains an argument of the given name.
*
* @exception IllegalStateException if accessed prior to parsing.
*/
public boolean hasArgument(String key);
/**
* Get this command's qualifiers.
*
* @exception IllegalStateException if accessed prior to parsing.
*/
public Map<String,String> getQualifiers();
/**
* Get the value of this command's qualifier of the given name.
*
* @return null if the qualifier does not exist.
*
* @exception IllegalStateException if accessed prior to parsing.
*/
public String getQualifier(String key);
/**
* Affirm this command contains an qualifier of the given name.
*
* @exception IllegalStateException if accessed prior to parsing.
*/
public boolean hasQualifier(String key);
}