Guava cache and preserving checked exceptions

Question

I'm refactoring some code to use guava Cache.

Initial code:

public Post getPost(Integer key) throws SQLException, IOException {     return PostsDB.findPostByID(key); } 

In order not to break something I need to preserve any thrown exception as is, without wrapping it.

Current solution appears somewhat ugly:

public Post getPost(final Integer key) throws SQLException, IOException {     try {         return cache.get(key, new Callable<Post>() {             @Override             public Post call() throws Exception {                 return PostsDB.findPostByID(key);             }         });     } catch (ExecutionException e) {         Throwable cause = e.getCause();         if (cause instanceof SQLException) {             throw (SQLException) cause;         } else if (cause instanceof IOException) {             throw (IOException) cause;         } else if (cause instanceof RuntimeException) {             throw (RuntimeException) cause;         } else if (cause instanceof Error) {             throw (Error) cause;         } else {             throw new IllegalStateException(e);         }     } } 

Is there any possible way to make it nicer?

Answer 1

Just after writing the question started thinking about utility method powered with generics. Then remembered something about Throwables. And yes, it's already there! )

It may also be necessary to handle UncheckedExecutionException or even ExecutionError.

So the solution is:

public Post getPost(final Integer key) throws SQLException, IOException {     try {         return cache.get(key, new Callable<Post>() {             @Override             public Post call() throws Exception {                 return PostsDB.findPostByID(key);             }         });     } catch (ExecutionException e) {         Throwables.propagateIfPossible(             e.getCause(), SQLException.class, IOException.class);         throw new IllegalStateException(e);     } catch (UncheckedExecutionException e) {         Throwables.throwIfUnchecked(e.getCause());         throw new IllegalStateException(e);     } } 

Very nice!

See also ThrowablesExplained, LoadingCache.getUnchecked and Why we deprecated Throwables.propagate.