How to create and apply DIFF programmatically?

General Discussion
1

The task is as follows: obtain a diff between the snapshot recorded on disk (an XML file) and the current database, and then store this diff to XML file
everything should work from @Configuration SpringBoot application:

 @Bean
 @Order(4)
 public CommandLineRunner initEverithing(ResourceLoader resourceLoader) { ... and so on

not from CLI but from SpringBoot application.

2

To perform diff with a file (“offline” in Liquibase), you need to provide a snapshot of the database, not the changelog. You create this with the snapshot command, formatted as JSON.

3

Is there only way the CLI? Is there any programmatic API?

4

You just take a snapshot in JSON format, and then when you run diff you specify that as the referenceURL argument, like offline:postgresql?snapshot=mysnapshot.json. The URL argument is for the database.

You can take snapshot by using the Liquibase API.

5

How to run diff and take snapshot using the Liquibase API? ChatGPT don’t know how

6

This method should work. You would need to write the contents of the OutputStream to disk as a temp file, and then use that in your offline URL that you pass to the diff command.

public static DatabaseSnapshot takeSnapshot(String url, Database database, String schemas, OutputStream stream) throws DatabaseException {

    DatabaseSnapshot snapshot = null;
    try {
        CommandScope snapshotCommand = new CommandScope("snapshot");
        snapshotCommand.addArgumentValue(DbUrlConnectionArgumentsCommandStep.DATABASE_ARG, database);
        snapshotCommand.addArgumentValue(SnapshotCommandStep.SCHEMAS_ARG, schemas);
        snapshotCommand.setOutput(stream);
        CommandResults results = snapshotCommand.execute();
        snapshot = (DatabaseSnapshot) results.getResult("snapshot");
    } catch (Exception e) {
        String message = "";
        if (database.getConnection() instanceof OfflineConnection) {
            message =
                "The snapshot specified in the URL property cannot be accessed. Database-scoped checks cannot be completed.\n" +
                "Please check all database properties and credentials and try again.";
        } else {
            message =
                "The database target specified in the URL property cannot be accessed. Database-scoped checks cannot be completed.\n" +
                "Please check all database properties and credentials and try again.";
        }
        throw new DatabaseException(message, e);
    }
    return snapshot;
}