Bugfixes, improvements, a meaningful commit message, A README FILE

README.md

@@ -0,0 +1,30 @@
+# Neo4JDemo
+This project is used for a lecture at the Johannes Kepler University Linz (JKU) in Austria. 
+You are free to using it also if you do not participate in the course. 
+
+---
+
+## Running
+ATTENTION: This application tries to create the subfolder 'database' in the working directory. 
+If a folder of the same name is already present, the application will abort. 
+Otherwise, the folder is deleted on application shutdown.
+
+### Requirements
+- Java 11 or above
+- A folder without 'database' in it
+
+### Running from the console
+1. Download the latest release at the releases page https://github.com/dahoat/neo4jdemo/releases
+1. Open a cmd/terminal/... and navigate to the JAR file
+1. Make sure no directory 'database' is present in the current directory
+1. Execute `java --illegal-access=permit -jar neo4jdemo.jar`
+1. Navigate to http://localhost:8080/
+1. When you are finished, click into the console and press [Ctrl]+[C] to shutdown the application
+1. Cleanup 'database' in case of an error. 
+
+### Running from your IDE
+Clone the project and set up the Spring Boot Application.  
+The Angular project located in the folder 'frontend' is only needed, if you would like to change the website with the examples. 
+In that case, you have to use the command `ng build-spring` which will compile the angular project and store the result in 'resources/static' in the Spring project.
+
+---

frontend/src/app/app.component.html

@@ -35,6 +35,77 @@ <h2>Basic building blocks</h2>
   <h2>Official Cypher Manual</h2>
   <a href="https://neo4j.com/docs/cypher-manual/current/" target="_blank">https://neo4j.com/docs/cypher-manual/current/</a>
 
+  <h2>Creating our First Entries</h2>
+
+  <div class="lecture-part">
+    We will start by creating our first node
+    <app-snippset query="CREATE ()"></app-snippset>
+    This only inserts an empty node into the database without a label or any content.
+  </div>
+
+  <div class="lecture-part">
+    So next, we create a node with the label <b>Student</b> and a name.
+    <app-snippset query="CREATE (n:Student{name: 'Alex'}) RETURN n"></app-snippset>
+    This time, the node is stored in the variable <b>n</b>, so we can <b>RETURN</b> it at the end of the query.
+  </div>
+
+  <div class="lecture-part">
+    We now also want to add a property <b>study</b> to our student.
+    What we need is to first get the node out of the database again using <b>MATCH</b> like this:
+    <app-snippset query="MATCH (n:Student{name: 'Alex'}) RETURN n"></app-snippset>
+    If this query returns our previously created node, we can enhance the query.
+    <app-snippset query="MATCH (n:Student{name: 'Alex'}) SET n.study = 'computer science' RETURN n"></app-snippset>
+    This gets the node out of the database, modifies it by adding the property study and then returns the modified version back to us.
+  </div>
+
+  <div class="lecture-part">
+    We still have the empty node in the database which we do not need any longer, so we want to remove it.
+    First, we have to make sure, we get match only the node we want to delete:
+    <app-snippset query="MATCH (n) RETURN n"></app-snippset>
+    This has the problem that we also get our students, so we need to filter them out:
+    <app-snippset query="MATCH (n) WHERE NOT n:Student RETURN n"></app-snippset>
+    We could also do this one for the case we have multiple labels in the database:
+    <app-snippset query="MATCH (n) WHERE size(labels(n)) = 0 RETURN n"></app-snippset>
+    For the actual deletion, we replace the <b>RETURN</b> part with <b>DELETE</b>:
+    <app-snippset query="MATCH (n) WHERE size(labels(n)) = 0 DELETE n"></app-snippset>
+  </div>
+
+  <div class="lecture-part">
+    To add some edges, we need more nodes, so we create a lecture, find our student and attach both with an edge.
+    <app-snippset query="CREATE (l:Lecture{topic: 'GraphDBs'}) WITH l MATCH (s:Student{name: 'Alex'}) WITH l, s CREATE (s)-[:LISTENS]->(l) RETURN *"></app-snippset>
+  </div>
+
+  <div class="lecture-part">
+    After Alex graduated, the nodes is eventually removed, so we try this query:
+    <app-snippset query="MATCH (s:Student{name: 'Alex'}) DELETE s" copy="false"></app-snippset>
+    Which won't execute because as Neo4J says <em>Cannot delete node<0>, because it still has relationships. To delete this node, you must first delete its relationships.</em>
+    Instead, we exlicilty need to state that we want also the relationships removed by
+    <app-snippset query="MATCH (s:Student{name: 'Alex'}) DETACH DELETE s"></app-snippset>
+  </div>
+
+  <div class="lecture-part">
+    Sometimes, we want a node, but are not sure, whether it is already existing.
+    For this case, we can use <b>MERGE</b> which tries to lookup a node and nothing is found, creates it as if <b>CREATE</b> was used.
+    For example, to add another student to our (existing) lecture:
+    <app-snippset query="MERGE (s:Student{name: 'Kim'}) WITH s MERGE (l:Lecture{topic: 'GraphDBs'}) WITH s, l MERGE (s)-[:LISTENS]->(l) RETURN *"></app-snippset>
+    ATTENTION: If we used
+    <app-snippset query="MERGE (s:Student{name: 'Kim'})-[:LISTENS]->(l:Lecture{topic: 'GraphDBs'}) RETURN *"></app-snippset>
+    We would have got another lecture about graph databases because Neo4J would be looking for a lecture with an incoming <b>LISTENS</b> edge attaching a student named Kim.
+    Actually if you use the second query, change the name and execute it, you would end up with another new lecture with only one student.
+  </div>
+
+  <div class="lecture-part">
+    To remove a property of a node, <b>REMOVE</b> is used and not DELETE.
+    <app-snippset query="MATCH (l:Lecture{topic: 'GraphDBs'}) REMOVE l.topic RETURN l"></app-snippset>
+  </div>
+
+  <div class="lecture-part">
+    At this point, we finished the basics of creating and deleting nodes and edges and now focus on fetching data.
+    Before that, we can clean up the database, either by
+    <app-snippset query="MATCH (n) DETACH DELETE n"></app-snippset>
+    Matching, detaching and deleting everything in the database, or simply use the button below.
+    <app-database-control button="clear"></app-database-control>
+  </div>
 
   <h2>Simple MATCH queries</h2>
 
@@ -108,9 +179,9 @@ <h2>Filtering with Properties</h2>
 
   <div class="lecture-part">
     We can also filter using all kinds of functions and combinations.
-    <app-snippset query="MATCH (n:Pokemon) WHERE n.name starts with 'pi' RETURN n"></app-snippset>
-    <app-snippset query="MATCH (n:Pokemon) WHERE n.name starts with 'pi' or n.name = 'charizard' RETURN n"></app-snippset>
-    <app-snippset query="MATCH (n:Pokemon) WHERE n.name starts with 'c' and n.pokedexId <= 150 RETURN n"></app-snippset>
+    <app-snippset query="MATCH (n:Pokemon) WHERE n.name STARTS WITH 'pi' RETURN n"></app-snippset>
+    <app-snippset query="MATCH (n:Pokemon) WHERE n.name STARTS WITH 'pi' or n.name = 'charizard' RETURN n"></app-snippset>
+    <app-snippset query="MATCH (n:Pokemon) WHERE n.name STARTS WITH 'c' and n.pokedexId <= 150 RETURN n"></app-snippset>
   </div>
 
   <h2>Filtering with Paths</h2>
@@ -146,7 +217,7 @@ <h2>Filtering with Paths</h2>
 
   <div class="lecture-part">
     For Pokemon with three evolutionary levels, we can use an abbreviation:
-    <app-snippset query="MATCH (p1:Pokemon)-[:EVOLVES_TO*3]->(p3:Pokemon) WHERE NOT (p3)-[:EVOLVES_TO]->() RETURN *"></app-snippset>
+    <app-snippset query="MATCH (p1:Pokemon)-[:EVOLVES_TO*2]->(p3:Pokemon) WHERE NOT (p3)-[:EVOLVES_TO]->() RETURN *"></app-snippset>
     Where we do not see the full path but only start end end.
     If we again store the paths in a variable, we get all three Pokemon.
     <app-snippset query="MATCH chain=(p1:Pokemon)-[:EVOLVES_TO*2]->(p3:Pokemon) WHERE NOT (p3)-[:EVOLVES_TO]->() RETURN *"></app-snippset>

frontend/src/app/components/browser/browser.component.html

@@ -14,5 +14,5 @@ <h2>Neo4J Browser</h2>
     <dt>Password</dt>
     <dd>&lt;empty&gt;</dd>
   </dl>
-  Basically, just click <button onclick="alert('Not here, in the Neo4J Browser...');">Connect</button>
+  Basically, just enter <em>localhost</em> in the URL and click <button onclick="alert('Not here, in the Neo4J Browser...');">Connect</button>
 </div>

frontend/src/index.html

@@ -2,7 +2,7 @@
 <html lang="en">
 <head>
   <meta charset="utf-8">
-  <title>Frontend</title>
+  <title>Neo4JDemo - Control Panel</title>
   <base href="/">
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <link rel="icon" type="image/x-icon" href="favicon.ico">

pom.xml

@@ -26,12 +26,6 @@
             <artifactId>spring-boot-starter-web</artifactId>
         </dependency>
 
-        <dependency>
-            <groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-devtools</artifactId>
-            <scope>runtime</scope>
-            <optional>true</optional>
-        </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-test</artifactId>

src/main/java/at/jku/faw/neo4jdemo/repository/CsvPokemonRepositoryImpl.java

@@ -1,6 +1,9 @@
 package at.jku.faw.neo4jdemo.repository;
 
 import at.jku.faw.neo4jdemo.model.csv.CsvPokemon;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.ResourceLoader;
 import org.springframework.stereotype.Repository;
 
 import java.io.IOException;
@@ -12,8 +15,9 @@ public class CsvPokemonRepositoryImpl extends GenericCsvRepositoryImpl implement
 
 	private final List<CsvPokemon> csvPokemon = new ArrayList<>();
 
-	public CsvPokemonRepositoryImpl() throws IOException {
-		csvPokemon.addAll(getCsvEntities("data/pokemon_species.csv", CsvPokemon.class));
+	public CsvPokemonRepositoryImpl(ResourceLoader resourceLoader) throws IOException {
+		Resource csvFile = resourceLoader.getResource("classpath:data/pokemon_species.csv");
+		csvPokemon.addAll(getCsvEntities(csvFile, CsvPokemon.class));
 	}
 
 	@Override

src/main/java/at/jku/faw/neo4jdemo/repository/CsvTypeRepositoryImpl.java

@@ -2,21 +2,12 @@
 
 import at.jku.faw.neo4jdemo.model.csv.CsvType;
 import at.jku.faw.neo4jdemo.model.csv.CsvTypeMapping;
-import com.opencsv.CSVReader;
-import com.opencsv.bean.CsvToBean;
-import com.opencsv.bean.CsvToBeanBuilder;
-import com.opencsv.bean.HeaderColumnNameMappingStrategy;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.ResourceLoader;
 import org.springframework.stereotype.Repository;
-import org.springframework.util.ResourceUtils;
 
-import java.io.BufferedReader;
-import java.io.File;
-import java.io.FileInputStream;
-import java.io.FileNotFoundException;
 import java.io.IOException;
-import java.io.InputStreamReader;
 import java.util.HashSet;
-import java.util.List;
 import java.util.Set;
 
 @Repository
@@ -25,9 +16,12 @@ public class CsvTypeRepositoryImpl extends GenericCsvRepositoryImpl implements C
 	private final Set<CsvTypeMapping> typeMappings = new HashSet<>();
 	private final Set<CsvType> types = new HashSet<>();
 
-	public CsvTypeRepositoryImpl() throws IOException {
-		this.typeMappings.addAll(getCsvEntities("data/pokemon_types.csv", CsvTypeMapping.class));
-		this.types.addAll(getCsvEntities("data/types.csv", CsvType.class));
+	public CsvTypeRepositoryImpl(ResourceLoader resourceLoader) throws IOException {
+		Resource csvPokemonTypesResource = resourceLoader.getResource("classpath:data/pokemon_types.csv");
+		Resource csvTypesResource = resourceLoader.getResource("classpath:data/types.csv");
+
+		this.typeMappings.addAll(getCsvEntities(csvPokemonTypesResource, CsvTypeMapping.class));
+		this.types.addAll(getCsvEntities(csvTypesResource, CsvType.class));
 	}
 
 	@Override

src/main/java/at/jku/faw/neo4jdemo/repository/GenericCsvRepositoryImpl.java

@@ -1,30 +1,20 @@
 package at.jku.faw.neo4jdemo.repository;
 
-import at.jku.faw.neo4jdemo.model.csv.CsvType;
 import com.opencsv.CSVReader;
 import com.opencsv.bean.CsvToBean;
 import com.opencsv.bean.CsvToBeanBuilder;
-import com.opencsv.bean.CsvToBeanFilter;
 import com.opencsv.bean.HeaderColumnNameMappingStrategy;
 import com.opencsv.enums.CSVReaderNullFieldIndicator;
-import org.springframework.util.ResourceUtils;
+import org.springframework.core.io.Resource;
 
 import java.io.BufferedReader;
-import java.io.File;
-import java.io.FileInputStream;
-import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStreamReader;
-import java.util.Arrays;
 import java.util.List;
 
 public abstract class GenericCsvRepositoryImpl {
-	private File getCsvFile(String path) throws FileNotFoundException {
-		return ResourceUtils.getFile("classpath:" + path);
-	}
-
-	protected <T> List<T> getCsvEntities(String csvFilePath, Class<T> entity) throws IOException {
-		try(CSVReader reader = new CSVReader(new BufferedReader(new InputStreamReader(new FileInputStream(getCsvFile(csvFilePath)))))) {
+	protected <T> List<T> getCsvEntities(Resource csvResource, Class<T> entity) throws IOException {
+		try(CSVReader reader = new CSVReader(new BufferedReader(new InputStreamReader(csvResource.getInputStream())))) {
 
 			HeaderColumnNameMappingStrategy<T> ms = new HeaderColumnNameMappingStrategy<>();
 			ms.setType(entity);

src/main/java/at/jku/faw/neo4jdemo/runner/Neo4JRunner.java

@@ -9,7 +9,6 @@
 import org.springframework.boot.ApplicationArguments;
 import org.springframework.boot.ApplicationRunner;
 import org.springframework.stereotype.Component;
-import org.springframework.util.ResourceUtils;
 
 import javax.annotation.PreDestroy;
 import java.io.File;
@@ -21,15 +20,20 @@
 public class Neo4JRunner implements ApplicationRunner {
 	private static final Logger logger = LoggerFactory.getLogger(Neo4JRunner.class);
 
+	private boolean cleanup = false;
 	private File dbDir;
 	private DatabaseManagementService dbms;
 
 	@Override
 	public void run(ApplicationArguments args) throws Exception {
 		dbDir = new File("database");
-		if (!dbDir.exists()) {
-			Files.createDirectory(dbDir.toPath());
+		if (dbDir.exists()) {
+			logger.error("The directory 'database' already exists. This application deletes this folder on shutdown. If it is your folder, move it somewhere else, if it belongs to a previous execution of this application, delete it.");
+			System.exit(1);
+			return;
 		}
+		cleanup = true;
+		Files.createDirectory(dbDir.toPath());
 
 		logger.warn("Database location is {}", dbDir.toPath().toAbsolutePath());
 
@@ -41,13 +45,22 @@ public void run(ApplicationArguments args) throws Exception {
 		if(db.isAvailable(10*1000)) {
 			logger.info("Neo4J is now available.");
 		}
+
 		logger.warn("Press [CTRL]+[C] to shutdown.");
 	}
 
 	@PreDestroy
 	public void onExit() {
-		logger.warn("Shutting database down.");
-		dbms.shutdown();
+		if (!cleanup) {
+			return;
+		}
+
+		try {
+			logger.warn("Shutting database down.");
+			dbms.shutdown();
+		} catch (Exception e) {
+			e.printStackTrace();
+		}
 
 		logger.warn("Deleting database directory.");
 		try {

src/main/resources/static/index.html

@@ -2,7 +2,7 @@
 <html lang="en">
 <head>
   <meta charset="utf-8">
-  <title>Frontend</title>
+  <title>Neo4JDemo - Control Panel</title>
   <base href="/">
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <link rel="icon" type="image/x-icon" href="favicon.ico">