@RobertCemper - our paths have crossed a time or two. I hope they will again.

Hi Enrico,

I am listening! $system.external does not replace the old Java Gateway but the old Java and JDBC Gateways should still be available. I am not intimately familiar with either of those although I did some of the refactoring work with them both. I am not aware of any user code changes that are necessary to keep using them.

If you want to use the new External Java Server then you will necessarily need to write new code. I am happy to provide demos showing how this can be done. I can also assist you with implementing your own project to get you started. Just let me know how you wish to proceed.

As for leveraging existing Java libraries, you should be able to do many things without writing new Java code but not everything. If you have some examples of libraries you have attempted to use but were not successful, please provide information so that I can attempt to replicate your issues.

As always, I am here, listening, and happy to help!!

-Dan

In general, a <LIST> error indicates a malformed $list value.

USER>set bad = "something wrong"   

USER>write $li(bad,1)

WRITE $LI(bad,1)
^
<LIST>
USER>set good = $listbuild("something right")

USER>write $li(good,1)
something right

In %SerializeObject, this typically is caused by an expectation that a value is a valid list but it is not. In a more complex class that extends %SerialObject, one that contains at least one property whose type class is a swizzlable (persistent, serial, stream), $list(value, n) is used to extract the object value (id or serial value) from a value that is expected to be an OID. While OID's an be more complex, the typical OID format is $list(<serialized object value>, <most specific type class>). <serialized object value> can be a simple ID and <most specific type class> (MSTC) is the class of which the object is an instance but not an instance of any subclass of MSTC.

That isn't the only possibility but it is the most likely. I can't be more specific without seeing the full class definition.

-Dan

I came up with this quick and dirty example. I did discover a problem when I executed this using the Database Console in IntelliJ - evidently the IRIS Server requires statement results to be only ResultSets! (I've reported that problem). If the result of executing the insert statements is not added to the %sqlcontext then this works through client connections, otherwise an error is reported. I'll include the result of executing this from the command line and then displaying the results. Also, the results from executing this from a client with the insert results suppressed.

DROPTABLEIFEXISTS demo_person;
DROPPROCEDUREIFEXISTS multi_results;
CREATETABLE demo_person (nameVARCHAR(20), age INT, home_city VARCHAR(40));
CREATEPROCEDURE multi_results() RESULTSETSLANGUAGE OBJECTSCRIPT
{
set ins = $system.SQL.Prepare("insert into demo_person(name, age, home_city) VALUES(?,?,?)")
do $system.SQL.Execute("TRUNCATE TABLE demo_person")
do %sqlcontext.AddResultSet(ins.execute("Dan", 25, "Miami"))
do %sqlcontext.AddResultSet(ins.execute("Jorge", 32, "Tampa"))
do %sqlcontext.AddResultSet(ins.execute("Enrico", 29, "Turin"))
do %sqlcontext.AddResultSet(ins.execute("Alexy", 21, "London"))
do %sqlcontext.AddResultSet($system.SQL.Execute("SELECT name, age, home_city FROM demo_person ORDER BY age DESC"))
};
CALL multi_results();

USER>set result = $system.SQL.Execute("call multi_results()")

USER>do result.%Display()

Dumping result #1
1 Row Affected

Dumping result #2
1 Row Affected

Dumping result #3
1 Row Affected

Dumping result #4
1 Row Affected

Dumping result #5
name    age    home_city
Jorge    32    Tampa
Enrico    29    Turin
Dan    25    Miami
Alexy    21    London

4 Rows(s) Affected

The results when not adding the insert results as displayed by a database console:

We posted a sample project to the community github account. There are java and dotnet versions of the project. Take a look and we would appreciate any feedback you may want to offer.

https://github.com/intersystems-community/samples-dynamicgateway-java

https://github.com/intersystems-community/samples-dynamicgateway-dotnet

Please note that there are some deficiencies when working with parameterized Java types when using the new External Java Server. Some of these were discovered during the refactoring of the %Net.Remote.Java.Test code. Some have already been addressed but not yet included in a release.

Hi,

When you say "purging" do you mean that you are deleting the class definition? Or do you simply mean that you are deleting the data - perhaps by invoking %DeleteExtent or %KillExtent?

IRIS has three types of Classes - datatypes (not instantiable), registered (instantiable), and dynamic (not registered but instantiable). Your question seems to involve only registered types. While any data can be serialized/deserialized, we define an interface for doing so - the so-called Storage Interface. Storage Definition is a class member that can be included in just about any class but we only recognize and process it when the class is either a serial or persistent class. A serial class is a class that extends %SerialObject (meaning that %SerialObject is in its primary superclass hierarchy) and a persistent class is a class that extends %Persistent (again, %Persistent is in its primary superclass hierarchy). For these classes, the class compiler will ensure there is a fully defined Storage Definition. As with all class members, the Storage Definition has a type class. This type class is often referred to as the Storage Class - it is a class that implements the Storage Interface. The Storage Definition defines the format of the serialized object. For serial classes, this serialized object value is not directly stored anywhere. Rather, the serialized value is expected to be stored as a value embedded inside of another object. For persistent classes, an object is serialized, perhaps into multiple nodes, and stored in a global at a location defined by the IDKEY index. Persistent classes can also use globals for storing other things such as indexes, counters, metadata and so on. The set of all globals used by a persistent class is referred to as the Extent Set which is, by default, registered with the Extent Manager.

When you remove the Storage Definition from a serial or persistent class, then it is possible that any existing data serialized using the removed Storage Definition will not be able to be deserialized as it might not be compatible with a newly defined Storage Definition. We only recommend removing a Storage Definition from a class if there are no serialized/stored instances of the class present.

When you delete a persistent class, you can also delete the data and the Extent Set by adding the /deleteextent qualifier (or the 'e' flag) to the command. You can also delete the data by invoking %DeleteExtent (logical delete) or %KillExtent (physical delete - no constraints are enforced). That only deletes the data and leaves the Extent Set registered with the Extent Manager. You can delete the Extent Set from the Extent Registry by using utilities we provide. Start here: https://docs.intersystems.com/irislatest/csp/documatic/%25CSP.Documatic…

I am happy to help if you wish (I wrote much of the core serialization/deserialization/storage code) but I will need to know more about the types of classes you are using and the issues you have.

-Dan

I can provide a solution for this but it comes with warnings - SQL doesn't do well with polymorphic embedded objects. If that isn't an issue then consider using a factory pattern. You must define a base class that extends %SerialObject and it must be instantiable. Then, override %OnNew() to dispatch to the concrete class that you wish to instantiate. Perhaps pass in a type argument. That %OnNew() can return an OREF (or a %Status if an error occurs).

If you are interested in this model then I can provide a small demo.

-Dan

You should be able to use Java 17 now for your projects. Are you specifically asking for when we will support Java 17 (and perhaps later versions) when using External Java Server/Java Gateway? If that is the case then I believe you can do that in 2024.1.0.

I am a huge fan of try/catch. The try is virtually cost-free with overhead only encountered when an exception is caught. I do agree with Jon Willeke - when I am in older code I normally do not refactor $ZTRAP unless the changes I have to make are more than a simple edit. I also use RETURN when exiting a function/method instead of QUIT.

It is possible to simluate a finally but it isn't as nice as having a real finally block would be.

Sorry - I just read Matt Gage's reply. My reply is redundant.

Actually, the problem is that %Exception.AbstractException already has five parameters. The error message you received is because the fifth argument has a type of %Exception.AbstractException and your fifth argument has a type of %String.

It is entirely possible to override the implementation of a member inherited from a super class so long as the inherited member is not defined as final and the signature of the local override is compatible with the inherited signature. The class compiler does perform a signature check to ensure the class does not violate the prime directive: Every instance of a class is implicitly a valid instance of its primary super class. Rewording that slightly - the interface of a class must be compatible with the interface of its primary super class. You can add new parameters to an inherited method but the existing parameters, those inherited, must declare a compatible type. A compatible type can be more specific (a subclass of the inherited type) but it cannot be a competely different type.

I tried adding a sixth parameter and also corrected the type of the fifth:

This class compiled cleanly.

ObjectScript does not allow method overloading which is a different thing.

The PackageDefinition class contains only packages where we need to keep metadata about a package. Most packages do not have any extra metadata.

The SQL solution is the correct solution IMO. If I were a developer on the Object team I would advocate for a method in $system.OBJ - PackageExists(<package_name>) perhaps. :)

@Andre Larsen Barbosa - I am the author of the intiial dynamic SQL 'feature'. I no longer work in this area and many significant enhancements have been made since my initial work. That said, I applaud your article. It is quite nice.

There is one feature that not many people know about - there is an Object mode that you can use with Dynamic Statement. Object mode is interesting when your query selects column values whose underlying type is a IRIS ObjectScript Class that is an object type (Persistent, Serial, Stream). Here is a trivial example of how it might be used.

LATEST:USER>set statement = ##class(%SQL.Statement).%New()

LATEST:USER>set statement.%ObjectSelectMode = 1

LATEST:USER>do statement.prepare("select name,address from person")

LATEST:USER>set result = statement.execute()

LATEST:USER>write result.%Next()
1
LATEST:USER>write result.name
po1
LATEST:USER>write result.address
7@User.Address
LATEST:USER>write result.address.city
Boston
LATEST:USER>write result.address.state
MA