Class MethodBaseQueryRedirector
- java.lang.Object
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- org.eclipse.persistence.queries.MethodBaseQueryRedirector
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- All Implemented Interfaces:
java.io.Serializable
,QueryRedirector
public class MethodBaseQueryRedirector extends java.lang.Object implements QueryRedirector
Purpose: Allows a class to be a
QueryRedirector
without implementingQueryRedirector
.Description: Normally to define a Redirector a Class must implement
QueryRedirector
and the requiredQueryRedirector.invokeQuery(DatabaseQuery, Record, Session)
.To maintain transparency it is possible to instead only define a static method that takes the same arguments as
invokeQuery
.An instance of
MethodBaseQueryRedirector
can be constructed, taking the name of that static method and theClass
in which it is defined as parameters.Whenever
invokeQuery
is called on this instance reflection will automatically be used to invoke the custom method instead.Advantages:
- The Redirector class and method name can be specified dynamically.
- The class containing the
invokeQuery
method does not need to implementQueryRedirector
. - The
invokeQuery
method can have any name. - The
invokeQuery
method can alternatively be defined to accept onlySession session
andVector arguments
as parameters.
- An extra step is added as the real
invokeQuery
method is called dynamically.
Example:
// First create a named query, define a redirector for it, and add the query // to the query manager. ReadObjectQuery query = new ReadObjectQuery(Employee.class); query.setName("findEmployeeByAnEmployee"); query.addArgument("employee"); MethodBaseQueryRedirector redirector = new MethodBaseQueryRedirector(QueryRedirectorTest.class, "findEmployeeByAnEmployee"); query.setRedirector(redirector); ClassDescriptor descriptor = getSession().getDescriptor(query.getReferenceClass()); descriptor.getQueryManager().addQuery(query.getName(), query); // Now execute the query by name, passing in an Employee as an argument. Vector arguments = new Vector(); arguments.addElement(employee); objectFromDatabase = getSession().executeQuery("findEmployeeByAnEmployee", Employee.class, arguments); // Note this Class does not implement QueryRedirector or method invokeQuery. public class QueryRedirectorTest { public static Object findEmployeeByAnEmployee(DatabaseQuery query, Record arguments, Session session) { ((ReadObjectQuery) query).setSelectionObject(arguments.get("employee")); return session.executeQuery(query); } }
- See Also:
QueryRedirector
, Serialized Form- Author:
- James Sutherland
- Since:
- TOPLink/Java 3.0
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Field Summary
Fields Modifier and Type Field Description protected java.lang.reflect.Method
method
protected java.lang.Class
methodClass
protected java.lang.String
methodClassName
protected java.lang.String
methodName
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Constructor Summary
Constructors Constructor Description MethodBaseQueryRedirector()
PUBLIC: Returns a new query redirector.MethodBaseQueryRedirector(java.lang.Class methodClass, java.lang.String methodName)
PUBLIC: Returns a new query redirector based on the static method in methodClass.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description protected java.lang.reflect.Method
getMethod()
INTERNAL: Returns the static method.java.lang.Class
getMethodClass()
PUBLIC: Returns the class to execute the static method on.java.lang.String
getMethodClassName()
INTERNAL: Returns the class to execute the static method on.java.lang.String
getMethodName()
PUBLIC: Returns the name of the static method.protected void
initializeMethod(DatabaseQuery query)
INTERNAL: Set the method.java.lang.Object
invokeQuery(DatabaseQuery query, Record arguments, Session session)
INTERNAL: Call the static method to execute the query.protected void
setMethod(java.lang.reflect.Method newMethod)
INTERNAL: Sets the static method.void
setMethodClass(java.lang.Class newMethodClass)
PUBLIC: Sets the class to execute the static method on.void
setMethodClassName(java.lang.String newMethodClassName)
INTERNAL: Sets the class to execute the static method on.void
setMethodName(java.lang.String newMethodName)
PUBLIC: Sets the name of the static method.
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Constructor Detail
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MethodBaseQueryRedirector
public MethodBaseQueryRedirector()
PUBLIC: Returns a new query redirector.
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MethodBaseQueryRedirector
public MethodBaseQueryRedirector(java.lang.Class methodClass, java.lang.String methodName)
PUBLIC: Returns a new query redirector based on the static method in methodClass.
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Method Detail
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getMethod
protected java.lang.reflect.Method getMethod()
INTERNAL: Returns the static method.
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getMethodClass
public java.lang.Class getMethodClass()
PUBLIC: Returns the class to execute the static method on.
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getMethodClassName
public java.lang.String getMethodClassName()
INTERNAL: Returns the class to execute the static method on.
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getMethodName
public java.lang.String getMethodName()
PUBLIC: Returns the name of the static method. This method must be public, static and have argument of DatabaseQuery, Vector, Session.- See Also:
setMethodName(java.lang.String)
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initializeMethod
protected void initializeMethod(DatabaseQuery query) throws QueryException
INTERNAL: Set the method.- Throws:
QueryException
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invokeQuery
public java.lang.Object invokeQuery(DatabaseQuery query, Record arguments, Session session)
INTERNAL: Call the static method to execute the query.- Specified by:
invokeQuery
in interfaceQueryRedirector
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setMethod
protected void setMethod(java.lang.reflect.Method newMethod)
INTERNAL: Sets the static method.
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setMethodClass
public void setMethodClass(java.lang.Class newMethodClass)
PUBLIC: Sets the class to execute the static method on.
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setMethodClassName
public void setMethodClassName(java.lang.String newMethodClassName)
INTERNAL: Sets the class to execute the static method on.
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setMethodName
public void setMethodName(java.lang.String newMethodName)
PUBLIC: Sets the name of the static method.This method must be public, static and have arguments of DatabaseQuery, Record, and Session.
The DatabaseQuery argument is the query that is currently being executed.
The Record will contain the Argument names added to the Query through addArgument(Sting) or, in the case of an Object query, the object attribute field names. These names will reference the argument values passed into the query, or in the case of an Object Query the values from the object.
The session argument is the session that the query is currently being executed on.
Alternatively the method can take only
(Session session, Vector arguments)
as parameters.
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