mike-jumper commented on a change in pull request #546:
URL: https://github.com/apache/guacamole-client/pull/546#discussion_r513946820
##########
File path:
guacamole/src/main/java/org/apache/guacamole/rest/connection/ConnectionResource.java
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@@ -150,18 +153,26 @@ public ConnectionResource(@Assisted UserContext
userContext,
* @throws GuacamoleException
* If an error occurs while retrieving the connection history.
*/
- @GET
+ @SuppressWarnings("deprecation")
@Path("history")
- public List<APIConnectionRecord> getConnectionHistory()
+ public ConnectionHistoryResource getConnectionHistory()
throws GuacamoleException {
- // Retrieve the requested connection's history
- List<APIConnectionRecord> apiRecords = new
ArrayList<APIConnectionRecord>();
- for (ConnectionRecord record : connection.getHistory())
- apiRecords.add(new APIConnectionRecord(record));
-
- // Return the converted history
- return apiRecords;
+ try {
+ return new
ConnectionHistoryResource(connection.getConnectionHistory());
+ }
+ catch (GuacamoleUnsupportedException e) {
+ try {
+ List<ConnectionRecord> history = Collections.emptyList();
+ for (ConnectionRecord record : connection.getHistory()) {
+ history.add(record);
+ }
+ return new ConnectionHistoryResource(new
SimpleActivityRecordSet<>(history));
+ }
+ catch (GuacamoleUnsupportedException ex) {
+ return new ConnectionHistoryResource(new
SimpleActivityRecordSet<>());
+ }
+ }
Review comment:
Ah, I see what you're saying. It's a rather confusing aspect of Java
generics. Consider if this was possible:
```java
List<FancyThing> a = new ArrayList<>();
List<? extends Thing> b = a; // This is completely OK
List<Thing> c = b; // This shouldn't be allowed because ...
c.add(new Thing()); // ... this breaks the contract of List<FancyThing>
```
Suddenly, that `List` that's expected to contain only fancy things contains
a non-fancy thing, breaking the contract of the type. Declaring something as
`List<Thing>` is saying "a list of `Thing` or any subclass of `Thing`".
Declaring something as `List<? extends Thing>` is saying "a list of **an
unspecified subclass of `Thing`**".
For the approach here with `SimpleActivityRecordSet`:
* There is a convenient way to turn `List<? extends T>` into `List<T>`,
[`Collections.unmodifiableList()`](https://docs.oracle.com/javase/8/docs/api/java/util/Collections.html#unmodifiableList-java.util.List-).
* If you're adding a convenience constructor to `SimpleActivityRecordSet()`
that accepts a list of records, you should probably use `List<? extends
RecordType>` for the parameter so that it can accept any `List` having usable
elements. This is what `ArrayList` does, presumably for the same reason:
https://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html#ArrayList-java.util.Collection-
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