docs

Author: andimarek-atlassian

content/documentation/v9/concerns.md

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+---
+title: "Concerns"
+date: 2018-09-09T12:52:46+10:00
+draft: false
+tags: [documentation]
+weight: 102
+description: Application concerns
+---
+# Application concerns
+
+The graphql-java library concentrates on providing an engine for the execution of queries according to the specification.
+
+It does not concern itself about other high level application concerns such as the following :
+
+- Database access
+- Caching data
+- Data authorisation
+- Data pagination
+- HTTP transfer
+- JSON encoding
+- Code wiring via dependency injection
+
+You need to push these concerns into your business logic layers.
+
+The following are great links to read more about this
+
+- http://graphql.org/learn/serving-over-http/
+- http://graphql.org/learn/authorization/
+- http://graphql.org/learn/pagination/
+- http://graphql.org/learn/caching/
+
+## Context Objects
+
+You can pass in a context object during query execution that will allow you to better invoke that business logic.
+
+For example the edge of your application could be performing user detection and you need that information inside the
+graphql execution to perform authorisation.
+
+This made up example shows how you can pass yourself information to help execute your queries.
+
+{{< highlight java "linenos=table" >}}
+
+        //
+        // this could be code that authorises the user in some way and sets up enough context
+        // that can be used later inside data fetchers allowing them
+        // to do their job
+        //
+        UserContext contextForUser = YourGraphqlContextBuilder.getContextForUser(getCurrentUser());
+
+        ExecutionInput executionInput = ExecutionInput.newExecutionInput()
+                .context(contextForUser)
+                .build();
+
+        ExecutionResult executionResult = graphQL.execute(executionInput);
+
+        // ...
+        //
+        // later you are able to use this context object when a data fetcher is invoked
+        //
+
+        DataFetcher dataFetcher = new DataFetcher() {
+            @Override
+            public Object get(DataFetchingEnvironment environment) {
+                UserContext userCtx = environment.getContext();
+                Long businessObjId = environment.getArgument("businessObjId");
+
+                return invokeBusinessLayerMethod(userCtx, businessObjId);
+            }
+        };
+
+{{< / highlight >}}