feat(GH-226): Support logging of the generated JPQL query string with debug log level (#227)

* feat: Added JPQL query string debug logging

* fix: removed canAccess check for Java 8 support

* fix: enable DEBUG logging level for Merge example app

* fix: polish log output formatting

* fix: Enabled JPQL query string debug logging for test coverage

Author: igdianov

graphql-jpa-query-example-merge/src/main/resources/application.yml

@@ -31,3 +31,7 @@ books:
   username: sa
   password: 
   driverClassName: org.h2.Driver
+
+logging:
+  level:
+    com.introproventures.graphql.jpa.query.schema: DEBUG

graphql-jpa-query-schema/src/main/java/com/introproventures/graphql/jpa/query/schema/impl/GraphQLJpaQueryDataFetcher.java

@@ -30,6 +30,11 @@
 import javax.persistence.criteria.Root;
 import javax.persistence.metamodel.EntityType;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.introproventures.graphql.jpa.query.introspection.ReflectionUtil;
+
 import graphql.language.Argument;
 import graphql.language.BooleanValue;
 import graphql.language.Field;
@@ -44,6 +49,8 @@
  *
  */
 class GraphQLJpaQueryDataFetcher extends QraphQLJpaBaseDataFetcher {
+    
+    private final static Logger logger = LoggerFactory.getLogger(GraphQLJpaQueryDataFetcher.class);
 
     private boolean defaultDistinct = true;
 
@@ -125,6 +132,9 @@ public Object get(DataFetchingEnvironment environment) {
             if(isDistinct) {
                 query.setHint(HIBERNATE_QUERY_PASS_DISTINCT_THROUGH, false);
             }
+            if (logger.isDebugEnabled()) {
+                logger.info("\nGraphQL JPQL Query String:\n    {}", getJPQLQueryString(query));
+            }
 
             // Let's execute query 
             List<?> resultList = query.getResultList(); 
@@ -239,4 +249,22 @@ public Page(Integer page, Integer size) {
         }
     }
 
+    protected String getJPQLQueryString(TypedQuery<?> query) {
+        try {
+            Object queryImpl = query.unwrap(TypedQuery.class);
+            
+            java.lang.reflect.Field queryStringField = ReflectionUtil.getField(queryImpl.getClass(),
+                                                                               "queryString");
+                                                    
+            ReflectionUtil.forceAccess(queryStringField);
+            
+            return queryStringField.get(queryImpl)
+                                   .toString();
+            
+        } catch (Exception ignored) {
+            logger.error("Error getting JPQL string", ignored);
+        }
+        
+        return null;
+    }
 }

graphql-jpa-query-schema/src/test/resources/application.properties

@@ -0,0 +1 @@
+logging.level.com.introproventures.graphql.jpa.query.schema=DEBUG