Exported FileExporter for Calendar json output file.

src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/business/EventBusiness.java

@@ -1,10 +1,6 @@
 package de.kreth.vaadin.clubhelper.vaadinclubhelper.business;
 
-import java.io.BufferedWriter;
-import java.io.File;
-import java.io.FileWriter;
 import java.io.IOException;
-import java.nio.file.Files;
 import java.security.GeneralSecurityException;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -52,26 +48,15 @@ public class EventBusiness {
 
 		List<ClubEvent> list = new ArrayList<>();
 
-		File f = new File("google_events.json");
-		if (f.exists()) {
-			try {
-				Files.delete(f.toPath());
-			} catch (IOException e) {
-				log.error("Error deleting file " + f.getAbsolutePath(), e);
-			}
-		}
-		try (BufferedWriter out = new BufferedWriter(new FileWriter(f))) {
-			
+		try (FileExporter ex = FileExporter.builder(log).setFileName("google_events.json").setAppend(false).disable().build()) {
+
 			String remoteHost = "localhost";
 			CalendarAdapter adapter = new CalendarAdapter();
 			List<com.google.api.services.calendar.model.Event> events = adapter
 					.getAllEvents(remoteHost);
 
 			for (com.google.api.services.calendar.model.Event ev : events) {
-				if (out != null) {
-					out.write(ev.toPrettyString());
-					out.newLine();
-				}
+				ex.writeLine(ev.toPrettyString());
 
 				if ("cancelled".equals(ev.getStatus())) {
 					log.debug("Cancelled: {}", ev.getSummary());
@@ -79,9 +64,12 @@ public class EventBusiness {
 					list.add(ClubEvent.parse(ev));
 				}
 			}
+			
 		} catch (GeneralSecurityException | IOException
 				| InterruptedException e) {
 			log.error("Error loading events from google.", e);
+		} catch (Exception e1) {
+			log.warn("Error closing " + FileExporter.class.getSimpleName(), e1);
 		}
 
 		return Collections.unmodifiableList(list);

src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/business/FileExporter.java

@@ -0,0 +1,119 @@
+package de.kreth.vaadin.clubhelper.vaadinclubhelper.business;
+
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.io.Writer;
+import java.nio.file.Files;
+
+import org.slf4j.Logger;
+
+/**
+ * Writes to a file catching all IOExceptions.
+ * @author markus
+ *
+ */
+public class FileExporter implements AutoCloseable {
+
+	private final Logger log;
+	private final BufferedWriter out;
+
+	public void writeLine(String prettyString) {
+		if (out != null) {
+			try {
+				out.write(prettyString);
+				out.newLine();
+			} catch (IOException e) {
+				log.error("Error on write operation.", e);
+			}
+		}
+	}
+	
+	public static Builder builder(Logger log) {
+		Builder b = new Builder();
+		b.setLog(log);
+		return b;
+	}
+	
+
+	public static class Builder {
+		
+		private Logger log;
+		private String fileName;
+		private boolean append = true;
+		private boolean enabled = true;
+		
+		private Builder() {
+		}
+		
+		public Builder setLog(Logger log) {
+			this.log = log;
+			return this;
+		}
+		
+		public Builder setFileName(String fileName) {
+			this.fileName = fileName;
+			return this;
+		}
+		
+		public Builder setAppend(boolean append) {
+			this.append = append;
+			return this;
+		}
+
+		public Builder setEnabled(boolean enabled) {
+			this.enabled = enabled;
+			return this;
+		}
+
+		public Builder disable() {
+			this.enabled = false;
+			return this;
+		}
+		
+		public FileExporter build() {
+			if (!enabled) {
+				return new FileExporter(log, null);
+			}
+			final File f = new File(fileName);
+			if (append == false) {
+
+				if (f.exists()) {
+					try {
+						Files.delete(f.toPath());
+					} catch (IOException e) {
+						log.error("Error deleting file " + f.getAbsolutePath(), e);
+					}
+				}
+			}
+			try {
+				return new FileExporter(this);
+			} catch (IOException e) {
+				log.error("Error creating Writer " + f.getAbsolutePath(), e);
+				log.warn("No Output written.");
+				return new FileExporter(log, null);
+			}
+		}
+	}
+
+	private FileExporter(Builder builder) throws IOException {
+		this(builder.log, new FileWriter(builder.fileName));
+	}
+
+	FileExporter(Logger log, Writer writer) {
+		this.log = log;
+		if (writer == null) {
+			this.out = null;
+		} else {
+			this.out = new BufferedWriter(writer);
+		}
+	}
+	@Override
+	public void close() throws Exception {
+		if (out != null) {
+			out.close();
+		}
+	}
+
+}