From b49e4c9f28c3fd2c89930c0cd7af8836d75ec2b2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andreas=20Sch=C3=A4rtl?= <andreas@schaertl.me>
Date: Thu, 21 May 2020 14:44:36 +0200
Subject: [PATCH] uloapi: GraphDB: improve error handling
---
.../info/mathhub/uloapi/query/GraphDB.java | 50 +++++++++++++++++--
1 file changed, 46 insertions(+), 4 deletions(-)
diff --git a/experimental/uloapi/src/main/java/info/mathhub/uloapi/query/GraphDB.java b/experimental/uloapi/src/main/java/info/mathhub/uloapi/query/GraphDB.java
index 0214feb..055c86d 100644
--- a/experimental/uloapi/src/main/java/info/mathhub/uloapi/query/GraphDB.java
+++ b/experimental/uloapi/src/main/java/info/mathhub/uloapi/query/GraphDB.java
@@ -36,6 +36,16 @@ public class GraphDB {
T op(RepositoryManager manager, Repository repository, RepositoryConnection connection);
}
+ /**
+ * Functional interface that defines a function that takes nothing, does something
+ * and returns nothing.
+ *
+ * Functional programmers hate this.
+ */
+ private interface Procedure {
+ void apply() throws Exception;
+ }
+
/**
* Run an operation on a remote repository.
*
@@ -52,6 +62,9 @@ public class GraphDB {
Repository repository = null;
RepositoryConnection connection = null;
+ Exception err = null;
+ T result = null;
+
try {
manager = new RemoteRepositoryManager(serverUrl);
manager.init();
@@ -61,20 +74,49 @@ public class GraphDB {
}
connection = repository.getConnection();
- return op.op(manager, repository, connection);
+ result = op.op(manager, repository, connection);
+ } catch (Exception e) {
+ err = e;
} finally {
if (connection != null) {
- connection.close();
+ err = chain(err, connection::close);
}
if (repository != null) {
- repository.shutDown();
+ err = chain(err, repository::shutDown);
}
if (manager != null) {
- manager.shutDown();
+ err = chain(err, manager::shutDown);
+ }
+ }
+
+ if (err != null) {
+ throw new OperationException("execute failed", err);
+ }
+
+ return result;
+ }
+
+ /**
+ * Execute proc and return {@code e} if not {@code null}, the exception
+ * caused by {@code proc} or {@code null}.
+ * @return If {@code e} is not {@code null}, always return {@code e}.
+ * Otherwise, if {@code proc} caused an exception, return that exception or
+ * return {@code null} if {@code proc} did not cause an exception.
+ */
+ private static Exception chain(Exception e, Procedure proc) {
+ Exception ret = e;
+
+ try {
+ proc.apply();
+ } catch (Exception ne) {
+ if (ret == null) {
+ ret = ne;
}
}
+
+ return ret;
}
}
--
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