org.apache.openjpa.persistence.jest.JESTCommand Maven / Gradle / Ivy
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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 find,
* query or domain. Besides signifying a JPA operation, a command may have
* zero or more qualifiers and arguments.
*
* A qualifier qualifies the action to be performed. For example, a query command may be qualified
* to return a single instance as its result, or limit its result to first 20 instances etc.
*
* An argument is an argument to the target JPA method. For example, find command has
* arguments for the type of the instance and the primary key. A query command has the
* query string as its argument.
*
* 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.
*
* 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
* http://www.jpa.com/jest/find/plan=myPlan?type=Person&1234
* with context root http://www.jpa.com/jest has the servlet path /find/plan=myPlan
* and query string type=Person&1234.
*
* The first path segment find will determine that the command is to find a
* persistent entity of type Person and primary key 1234 using a fetch plan
* named myPlan.
*
* @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 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 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);
}