fskorgen opened a new issue, #8357:
URL: https://github.com/apache/hop/issues/8357
### Apache Hop version?
2.20
### Java version?
21
### Operating system
Windows
### What happened?
## Problem
When changing the connection type of an existing database connection — for
example from MySQL to
MariaDB, to use another driver for the same server — Hop clears the
hostname, database name,
username and password, and replaces the port with the new type's default.
Changing the adapter should not require entering the same connection details
again. The password in
particular cannot be read back off the screen. The same applies when
switching to a different
database family, MySQL to SQL Server, say: host, database name, user and
password are still what
the user typed, and most of them still apply. This is even more so when the
fields hold variables
rather than literal values — `${DB_HOST}`, `${DB_USER}`, `${DB_PASSWORD}` —
which is how we set up
most connections: the variable names are the same whatever the database
type, so nothing about
them needs to change. It is easier to correct one field than to re-enter all
of them.
## Steps to reproduce
`main` @ `e487fe70f5`.
1. Metadata perspective → Relational Database Connection → open one with
hostname, database name,
username and password filled in (MySQL, say).
2. Change **Connection type** to a type not selected before in this editor
session — MariaDB,
PostgreSQL, Infobright.
3. Hostname, database name, username and password are empty. Port is the new
type's default.
Switching *back* to the type you started on restores its values.
## Expected behavior
- Preserve the connection details on every type change — within a family and
across families —
including an explicitly entered port or a variable reference in the port
field.
- If the port field is empty, use the selected type's default port if it has
one; otherwise leave
it empty.
- Preserve type-specific settings when switching back to a previously
selected type — that already
works today.
## Why
`DatabaseMetaEditor.changeConnectionType()` (`:549`) first calls
`DatabaseMeta.setDatabaseType`
(`core/.../DatabaseMeta.java:298`), which builds the new `IDatabase` and
copies the common
connection fields onto it. The next line (`:580`) replaces that instance
with one from `metaMap`:
```java
databaseMeta.setDatabaseType(newTypeName);
// :577
databaseMeta.setIDatabase(metaMap.get(databaseMeta.getIDatabase().getClass()));
// :580
```
`metaMap` is pre-filled by `populateMetaMap()` (`:170`) with an empty
instance of every database
plugin, initialized with the type's default port and default options. On the
first switch to a type
the lookup hits that empty instance, and the fields just copied are gone.
## Proposed fix
Keep the cached instance for its type-specific settings, then copy the
current connection details
(hostname, database name, username, password, servername, tablespaces,
access type) onto it. For
the port: copy it when it is filled in; when it is empty, use the selected
type's default if
available — otherwise leave it empty — instead of restoring an old cached
port.
One method plus a small private helper in `DatabaseMetaEditor`. Happy to
open the PR if the
approach looks right.
Once the port survives a type change, the obvious follow-up question is how
to get the new type's
default when you do want it. We answered that with a small **Default port**
button to the right of
the port field: it fills in the selected type's `getDefaultDatabasePort()`
on demand, and is only
shown for types that declare one. It is the piece that makes "keep the port"
safe to do without a
heuristic. Happy to include it in the same PR, or propose it separately if
you would rather keep the
defect fix minimal.
### Issue Priority
Priority: 3
### Issue Component
Component: Hop Gui
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