How does one use user-defined stored java functions with embedded hsql?

I’m using libreoffice on macOS 11.6.7 (Big Sur). I have created a database in Base using the embedded HSQL DB. Tables, queries, and forms are all working wonderfully.

I need to create some user-defined stored functions in java that will be called via SQL statements. Unfortunately, no matter what I’ve tried, I cannot get Base/embedded HSQL to execute the functions I have written in java. I have set the classpath within Base to include the JAR file in which my functions are located. Every time I try to call one of my functions using the “Execute SQL Statement” tool, I get the following error:

Access is denied: Myfuncs.trivial in statement [CALL “Myfuncs.trivial”(]

where “Myfuncs.trivial” is the name of the class and static function I am attempting to call.

I am able to call functions that are built in to java (e.g. java.lang.Math.sqrt), but I cannot call any functions that are in my JAR. Note that I can call my functions without any problems from other java code when my JAR is in java’s classpath, so I know that they actually work.

How does one get Base’s embedded HSQL DB to call user-defined java functions?

I’ve boiled things down to a very trivial test case:

CALL “Myfuncs.trivial”(2.0);

should call the following function which is in my JAR:

public final class Myfuncs {
public static double trivial( double d ) {
return java.lang.Math.sqrt( d );

For reference, the following works:

CALL “java.lang.Math.sqrt”(2.0);

However, trying to call Myfuncs.trivial always gives the “Access is denied” error.

Any help would be greatly appreciated.

this is likely more to do with the database than with LibreOffice Base. Base is just the front end to the database.
A big issue here is the embedded database is HSQLDB v1.8 (very old) and looking at that documentation I do not see (quick look) reference to user functions.
However in v2.3.4 and later versions (chapter numbers may vary in later versions) there is talk in Chapter 8. SQL-Invoked Routines and Chapter 10. Built In Functions. That versions documentation can be found here →

Hi Ratslinger,

Thank you for the quick reply.

Yes, the embedded version of HSQL in Base is quite old. However, in chapter 9 of the documentation for HSQL 1.8 (the version embedded in Base), it explicitly states that java-based stored procedures are supported and gives (somewhat brief) instructions about how to do it (see the section titled “Stored Procedures / Functions”). Those are the instructions that I have followed.

As I mentioned in my original post, I can successfully call various functions that are built in to Java, but can’t seem to call any functions provided by any JARs not shipped with Java (my own or third-party). I think there is a key piece missing in the brief instructions in HSQL 1.8’s documentation or something I’ve missed in LibreOffice to allow the functionality.

How to install Java (JRE/JDK) so that LibreOffice could use it?

@Hrbrgr as hsql1.8 is obviously already running java is installed and working. See:

The question here is about “stored procedures” like getting a self written java routine to work with the embedded database (hsql1.8)

1 Like

Had not sen that section buried in the manual. Have no immediate answer.
Possibly search the HSQL discussion board and/or ask there. HyperSQL Database Engine (HSQLDB) Discussion

@vaquero: Could you upload your *.jar-file here for testing?

While looking for something else, ran across this in the HSQL discussion board:

You can write a user-defined function in Java and link it in HSQLDB with CREATE FUNCTION to perform any timestamp conversion that you need.

from this post → HyperSQL Database Engine (HSQLDB) / Discussion / Help: TIMESTAMP and AT LOCAL behavior
Do not find CREATE FUNCTION in v1.8.x but in v 2.3.4 docs (Ch 4 under Routine Creation) is this:

An example is given below for a function defined as a Java method, then redefined as an SQL function.

CREATE FUNCTION zero_pad(x BIGINT, digits INT, maxsize INT)
SPECIFIC zero_pad_01
EXTERNAL NAME 'CLASSPATH:org.hsqldb.lib.StringUtil.toZeroPaddedString';

SET str = CAST(x AS VARCHAR(128));
SET str = SUBSTRING('0000000000000' FROM 1 FOR digits - CHAR_LENGTH(str)) + str;
return str;

Thought it may be relevant.

@RobertG: Here is a JAR you can test with. It contains a single function which should be callable as:

CALL “Myfuncs.trivial”(2.0);

All the function does is return the square root of the number passed to the function (in this case, the square root of 2.0).

Due to the upload filtering, I had to name the file mylib.pdf. You will need to rename it to mylib.jar.

mylib.pdf (678 Bytes)

I guess this is one of the crucial points.

  • Adding a jar to the class-path makes this available to LibreOffice
  • To be checked: Can HSQLDB also “see” all items in additional jars or is HSQLDB isolated.
  • We have to tell hsqldb where to find the additional routines, therefore the EXTERNAL-reference in the code.

No clue how to do this with the embedded 1.8

Not entirely certain that it is possible on LO for MacOS if the simple classpath declaration doesn’t work.