The CREATE FUNCTION statement defines a callable function or procedure.
You can also use the CREATE PROCEDURE statement to define a callable function or procedure, which are also known as routines.
The CREATE FUNCTION and CREATE PROCEDURE statements define a callable function or procedure, also known as a routine.
In previous versions of this product, CREATE FUNCTION and CREATE PROCEDURE had different uses and different capabilities. Subsequent enhancements have resulted in very few differences, which are listed in notes 1 and 3 below the syntax diagram.
Routines are useful for creating reusable blocks of code that can be executed independently many times. They can be implemented as a series of ESQL statements, a Javaâ„¢ method, or a database stored procedure. This flexibility means that some of the clauses in the syntax diagram are not applicable (or allowed) for all types of routine.
Each routine has a name, which must be unique within the schema to which it belongs. Routine names therefore cannot be overloaded; if the broker detects that a routine has been overloaded, it raises an exception.
Specify the routine's name using the RoutineName clause, and the routine's parameters using the ParameterList clause. If the LANGUAGE clause specifies ESQL, the routine must be implemented using a single ESQL statement. This statement is most useful if it is a compound statement (BEGIN ... END), because it can then contain as many ESQL statements as necessary to fulfil its function.
Alternatively, instead of providing an ESQL body for the routine, you can specify a LANGUAGE clause other than ESQL. You can then use the EXTERNAL NAME clause to provide a reference to the actual body of the routine, wherever it is located externally to the broker. For more details about using the EXTERNAL NAME clause, see Invoking stored procedures and Calling a Java routine.
Routines of any LANGUAGE type can have IN, OUT, and INOUT parameters. The caller can pass several values into the routine, and receive back several updated values. These returned parameters are in addition to any RETURNS clause that you have defined for the routine. The RETURNS clause defines the value that the routine returns to the caller.
Routines that are implemented in different languages have their own restrictions on which data-types can be passed in or returned; these restrictions are documented below. The data-type of the returned value must match the data-type of the value that is defined to be returned from the routine. Also, if a routine is defined to have a return value, the caller of the routine cannot ignore it. For more details see the CALL statement.
For any language or routine type, the method of invocation of the routine must match the manner of declaration of the routine. If the routine has a RETURNS clause, use either the FUNCTION invocation syntax or a CALL statement with an INTO clause. Conversely, if a routine has no RETURNS clause, you must use a CALL statement without an INTO clause.
If the routine type is FUNCTION, the direction indicator (IN, OUT, INOUT) is optional for each parameter. However, it is good programming practice to specify a direction indicator for all new routines of any type for documentation purposes.
ESQL variables that are declared to be CONSTANT (or references to variables declared to be CONSTANT) are not allowed to have the direction OUT or INOUT.
ESQL routines are written in ESQL, and have a LANGUAGE clause of ESQL. The body of an ESQL routine is typically a compound statement of the form BEGIN … END, containing multiple statements for processing the parameters passed to the routine.
CREATE PROCEDURE swapParms ( IN parm1 CHARACTER, OUT parm2 CHARACTER, INOUT parm3 CHARACTER ) BEGIN SET parm2 = parm3; SET parm3 = parm1; END;
This example procedure shows the recursive use of an ESQL routine. It parses a tree, visiting all places at and below the specified starting point, and reports what it has found:
SET OutputRoot.MQMD = InputRoot.MQMD; DECLARE answer CHARACTER; SET answer = ''; CALL navigate(InputRoot.XMLNS, answer); SET OutputRoot.XMLNS.Data.FieldNames = answer; CREATE PROCEDURE navigate (IN root REFERENCE, INOUT answer CHARACTER) BEGIN SET answer = answer || 'Reached Field... Type:' || CAST(FIELDTYPE(root) AS CHAR)|| ': Name:' || FIELDNAME(root) || ': Value :' || root || ': '; DECLARE cursor REFERENCE TO root; MOVE cursor FIRSTCHILD; IF LASTMOVE(cursor) THEN SET answer = answer || 'Field has children... drilling down '; ELSE SET answer = answer || 'Listing siblings... '; END IF; WHILE LASTMOVE(cursor) DO CALL navigate(cursor, answer); MOVE cursor NEXTSIBLING; END WHILE; SET answer = answer || 'Finished siblings... Popping up '; END;
When given the following input message:
<Person> <Name>John Smith</Name> <Salary period='monthly' taxable='yes'>-1200</Salary> </Person>
the procedure produces the following output, which has been manually formatted:
Reached Field... Type:16777232: Name:XML: Value :: Field has children... drilling down Reached Field... Type:16777216: Name:Person: Value :: Field has children... drilling down Reached Field... Type:16777216: Name:Name: Value :John Smith: Field has children... drilling down Reached Field... Type:33554432: Name:: Value :John Smith: Listing siblings... Finished siblings... Popping up Finished siblings... Popping up Reached Field... Type:16777216: Name:Salary: Value :-1200: Field has children... drilling down Reached Field... Type:50331648: Name:period: Value :monthly: Listing siblings... Finished siblings... Popping up Reached Field... Type:50331648: Name:taxable: Value :yes: Listing siblings... Finished siblings... Popping up Reached Field... Type:33554432: Name:: Value :-1200: Listing siblings... Finished siblings... Popping up Finished siblings... Popping up Finished siblings... Popping up Finished siblings... Popping up
>>--"-- className---.---methodName--"--------------><where className identifies the class that contains the method and methodName identifies the method to be invoked. If the class is part of a package, the class identifier part must include the complete package prefix; for example, "com.ibm.broker.test.MyClass.myMethod".
To find the Java class, the broker uses the search method described in Deploying Java classes.
public static <return-type> <method-name> (< 0 - N parameters>)
where <return-type> must be in the list of Java IN data types in the table in ESQL to Java data type mapping (excluding the REFERENCE type, which is not permitted as a return value), or the Java void data type. The parameter data types must also be in the ESQL to Java data type mapping table. In addition, the Java method is not allowed to have an exception throws clause in its signature.
You can use the Java user-defined node API in your Java method, provided that you observe the restrictions documented in Restrictions on Java routines. For more information about using the Java API, see Compiling a Java user-defined node.
This routine contains three parameters of varying directions, and returns an integer, which maps to a Java return type of java.lang.Long.
CREATE FUNCTION myProc1( IN P1 INTEGER, OUT P2 INTEGER, INOUT P3 INTEGER ) RETURNS INTEGER LANGUAGE JAVA EXTERNAL NAME "com.ibm.broker.test.MyClass.myMethod1";
You can use the following ESQL to invoke myProc1:
CALL myProc1( intVar1, intVar2, intVar3) INTO intReturnVar3; -- or SET intReturnVar3 = myProc1( intVar1, intVar2, intVar3);
This routine contains three parameters of varying directions and has a Java return type of void.
CREATE PROCEDURE myProc2( IN P1 INTEGER, OUT P2 INTEGER, INOUT P3 INTEGER ) LANGUAGE JAVA EXTERNAL NAME "com.ibm.broker.test.MyClass.myMethod2";
You must use the following ESQL to invoke myProc2:
CALL myProc2(intVar1, intVar2, intVar3);
The following Java class provides a method for each of the preceding Java examples:
package com.ibm.broker.test; class MyClass { public static Long myMethod1( Long P1, Long[] P2 Long[] P3) { ... } public static void myMethod2( Long P2, Long[] P2 Long[] P3) { ... } /* When either of these methods is called: P1 may or may not be NULL (depending on the value of intVar1). P2[0] is always NULL (whatever the value of intVar2). P3[0] may or may not be NULL (depending on the value of intVar3). This is the same as with LANGUAGE ESQL routines. When these methods return: intVar1 is unchanged intVar2 may still be NULL or may have been changed intVar3 may contain the same value or may have been changed. This is the same as with LANGUAGE ESQL routines. When myMethod1 returns: intReturnVar3 is either NULL (if the method returns NULL) or it contains the value returned by the method. */ }
ESQL data types 1 | Java IN data types | Java INOUT and OUT data types |
INTEGER, INT | java.lang.Long | java.lang.Long [] |
FLOAT | java.lang.Double | java.lang.Double[] |
DECIMAL | java.math.BigDecimal | java.math.BigDecimal[] |
CHARACTER, CHAR | java.lang.String | java.lang.String[] |
BLOB | byte[] | byte[][] |
BIT | java.util.BitSet | java.util.BitSet[] |
DATE | com.ibm.broker.plugin.MbDate | com.ibm.broker.plugin.MbDate[] |
TIME 2 | com.ibm.broker.plugin.MbTime | com.ibm.broker.plugin.MbTime[] |
GMTTIME 2 | com.ibm.broker.plugin.MbTime | com.ibm.broker.plugin.MbTime[] |
TIMESTAMP 2 | com.ibm.broker.plugin.MbTimestamp | com.ibm.broker.plugin.MbTimestamp[] |
GMTTIMESTAMP 2 | com.ibm.broker.plugin.MbTimestamp | com.ibm.broker.plugin.MbTimestamp[] |
INTERVAL | Not supported | Not supported |
BOOLEAN | java.lang.Boolean | java.lang.Boolean[] |
REFERENCE (to a message tree) 3 4 5 6 | com.ibm.broker.plugin.MbElement | com.ibm.broker.plugin.MbElement[] (Supported for INOUT. Not supported for OUT) |
ROW | Not supported | Not supported |
LIST | Not supported | Not supported |
For example, if an ESQL reference to OutputRoot.XML.Test is passed into a Java method as an INOUT MbElement, but a different MbElement is passed back to ESQL when the call returns, the different element must also point to somewhere in the OutputRoot tree.
A REFERENCE to a scalar variable can be used in the CALL of a Java method, provided that the data type of the variable the reference refers to matches the corresponding data type in the Java program signature.
You can create threads inside your method. However, created threads must not use the Java APIs, and you must return control back to the broker.
All restrictions that apply to the usage of the Java API also apply to Java methods that are called from ESQL.
The most efficient and flexible method of deploying to the broker is to add your JAR file to the bar file.
You can add a JAR file to the bar file manually, or automatically by using the tooling. The simplest way to add a JAR file to a bar file is to use the tooling.
If the tooling finds the correct Java class inside a referenced Java project open in the workspace, it automatically compiles the Java class into a JAR file and adds it to the bar file. This procedure is the same procedure that you follow to deploy a JavaCompute node inside a JAR, as described in User-defined node classloading.
When you deploy a JAR file from the tooling, a redeploy of the bar file containing the JAR file causes the referenced Java classes to be reloaded by the flow that has been redeployed. The files are also reloaded if the message flow that references a Java class is stopped and restarted. Ensure that you stop and restart (or redeploy) all flows that reference the JAR file that you want to update. This action avoids the problem of some flows running with the old version of the JAR file and other flows running with the new version.
The tooling deploys only JAR files; it does not deploy standalone Java class files.
You must complete this action manually; you cannot use the tooling.
In this method, redeploying the message flow does not reload the referenced Java classes; neither does stopping and restarting the message flow. The only way to reload the classes in this case is to stop and restart the broker itself.
To enable the broker to find a Java class, ensure that it is in one of the above locations. If the broker cannot find the specified class, it throws an exception.
Although you have the choices shown above when you deploy the JAR file, using the tooling to deploy the bar file provides the greatest flexibility when redeploying the JAR file.