Remove Guava dependency (close #320)

For PR #351.

* Change Preconditions to normal Java

* Replace ImmutableMap and Lists

Author: mscwilson

build.gradle

@@ -75,9 +75,6 @@ dependencies {
     // Jackson JSON processor
     api 'com.fasterxml.jackson.core:jackson-databind:2.13.3'
 
-    // Preconditions
-    api 'com.google.guava:guava:31.1-jre'
-
     // Testing libraries
     testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.2'
     testCompileOnly 'junit:junit:4.13.2'

examples/simple-console/src/main/java/com/snowplowanalytics/Main.java

@@ -20,10 +20,10 @@
 import com.snowplowanalytics.snowplow.tracker.events.*;
 import com.snowplowanalytics.snowplow.tracker.payload.SelfDescribingJson;
 
-import java.util.List;
+import java.util.Collections;
 import static java.util.Collections.singletonList;
+import java.util.List;
 
-import com.google.common.collect.ImmutableMap;
 
 public class Main {
 
@@ -61,7 +61,7 @@ public static void main(String[] args) throws InterruptedException {
         List<SelfDescribingJson> context = singletonList(
             new SelfDescribingJson(
                 "iglu:com.snowplowanalytics.iglu/anything-c/jsonschema/1-0-0",
-                ImmutableMap.of("foo", "bar")));
+                Collections.singletonMap("foo", "bar")));
 
         // This is an example of a eventSubject for adding user data
         Subject eventSubject = new Subject.SubjectBuilder().build();
@@ -111,7 +111,7 @@ public static void main(String[] args) throws InterruptedException {
         SelfDescribing selfDescribing = SelfDescribing.builder()
             .eventData(new SelfDescribingJson(
                     "iglu:com.snowplowanalytics.iglu/anything-a/jsonschema/1-0-0",
-                    ImmutableMap.of("foo", "bar")
+                    Collections.singletonMap("foo", "bar")
             ))
             .customContext(context)
             .build();

src/main/java/com/snowplowanalytics/snowplow/tracker/Tracker.java

@@ -12,8 +12,6 @@
  */
 package com.snowplowanalytics.snowplow.tracker;
 
-import com.google.common.base.Preconditions;
-
 import com.snowplowanalytics.snowplow.tracker.constants.Constants;
 import com.snowplowanalytics.snowplow.tracker.constants.Parameter;
 import com.snowplowanalytics.snowplow.tracker.emitter.Emitter;
@@ -41,11 +39,15 @@ public class Tracker {
     private Tracker(TrackerBuilder builder) {
 
         // Precondition checks
-        Preconditions.checkNotNull(builder.emitter);
-        Preconditions.checkNotNull(builder.namespace);
-        Preconditions.checkNotNull(builder.appId);
-        Preconditions.checkArgument(!builder.namespace.isEmpty(), "namespace cannot be empty");
-        Preconditions.checkArgument(!builder.appId.isEmpty(), "appId cannot be empty");
+        Objects.requireNonNull(builder.emitter);
+        Objects.requireNonNull(builder.namespace);
+        Objects.requireNonNull(builder.appId);
+        if (builder.namespace.isEmpty()) {
+            throw new IllegalArgumentException("namespace cannot be empty");
+        }
+        if (builder.appId.isEmpty()) {
+            throw new IllegalArgumentException("appId cannot be empty");
+        }
 
         this.parameters = new TrackerParameters(builder.appId, builder.platform, builder.namespace, Version.TRACKER, builder.base64Encoded);
         this.emitter = builder.emitter;

src/main/java/com/snowplowanalytics/snowplow/tracker/emitter/BatchEmitter.java

@@ -16,13 +16,13 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 
-import com.google.common.base.Preconditions;
 import com.snowplowanalytics.snowplow.tracker.constants.Constants;
 import com.snowplowanalytics.snowplow.tracker.constants.Parameter;
 import com.snowplowanalytics.snowplow.tracker.http.HttpClientAdapter;
@@ -203,13 +203,20 @@ protected BatchEmitter(final Builder<?> builder) {
         OkHttpClient client;
 
         // Precondition checks
-        Preconditions.checkArgument(builder.threadCount > 0, "threadCount must be greater than 0");
-        Preconditions.checkArgument(builder.batchSize > 0, "batchSize must be greater than 0");
+        if (builder.threadCount <= 0) {
+            throw new IllegalArgumentException("threadCount must be greater than 0");
+        }
+        if (builder.batchSize <= 0) {
+            throw new IllegalArgumentException("batchSize must be greater than 0");
+        }
+        if (builder.bufferCapacity <= 0) {
+            throw new IllegalArgumentException("bufferCapacity must be greater than 0");
+        }
 
         if (builder.httpClientAdapter != null) {
             httpClientAdapter = builder.httpClientAdapter;
         } else {
-            Preconditions.checkNotNull(builder.collectorUrl, "Collector url must be specified if not using a httpClientAdapter");
+            Objects.requireNonNull(builder.collectorUrl, "Collector url must be specified if not using a httpClientAdapter");
 
             if (builder.cookieJar != null) {
                 client = new OkHttpClient.Builder()
@@ -299,7 +306,9 @@ public List<TrackerPayload> getBuffer() {
      */
     @Override
     public void setBatchSize(final int batchSize) {
-        Preconditions.checkArgument(batchSize > 0, "batchSize must be greater than 0");
+        if (batchSize <= 0) {
+            throw new IllegalArgumentException("batchSize must be greater than 0");
+        }
         this.batchSize = batchSize;
     }
 

src/main/java/com/snowplowanalytics/snowplow/tracker/events/AbstractEvent.java

@@ -16,9 +16,7 @@
 import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.List;
-
-// Google
-import com.google.common.base.Preconditions;
+import java.util.Objects;
 
 // This library
 import com.snowplowanalytics.snowplow.tracker.Subject;
@@ -104,7 +102,7 @@ public static Builder<?> builder() {
     protected AbstractEvent(Builder<?> builder) {
 
         // Precondition checks
-        Preconditions.checkNotNull(builder.context);
+        Objects.requireNonNull(builder.context);
 
         this.context = builder.context;
         this.trueTimestamp = builder.trueTimestamp;

src/main/java/com/snowplowanalytics/snowplow/tracker/events/EcommerceTransaction.java

@@ -16,9 +16,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
-
-// Google
-import com.google.common.base.Preconditions;
+import java.util.Objects;
 
 // This library
 import com.snowplowanalytics.snowplow.tracker.constants.Parameter;
@@ -214,10 +212,12 @@ protected EcommerceTransaction(Builder<?> builder) {
         super(builder);
 
         // Precondition checks
-        Preconditions.checkNotNull(builder.orderId);
-        Preconditions.checkNotNull(builder.totalValue);
-        Preconditions.checkNotNull(builder.items);
-        Preconditions.checkArgument(!builder.orderId.isEmpty(), "orderId cannot be empty");
+        Objects.requireNonNull(builder.orderId);
+        Objects.requireNonNull(builder.totalValue);
+        Objects.requireNonNull(builder.items);
+        if (builder.orderId.isEmpty()) {
+            throw new IllegalArgumentException("orderId cannot be empty");
+        }
 
         this.orderId = builder.orderId;
         this.totalValue = builder.totalValue;

src/main/java/com/snowplowanalytics/snowplow/tracker/events/EcommerceTransactionItem.java

@@ -12,15 +12,13 @@
  */
 package com.snowplowanalytics.snowplow.tracker.events;
 
-// Google
-
-import com.google.common.base.Preconditions;
-
 // This library
 import com.snowplowanalytics.snowplow.tracker.constants.Parameter;
 import com.snowplowanalytics.snowplow.tracker.constants.Constants;
 import com.snowplowanalytics.snowplow.tracker.payload.TrackerPayload;
 
+import java.util.Objects;
+
 /**
  * Constructs an EcommerceTransactionItem object.
  * <p>
@@ -155,12 +153,16 @@ protected EcommerceTransactionItem(Builder<?> builder) {
         super(builder);
 
         // Precondition checks
-        Preconditions.checkNotNull(builder.itemId);
-        Preconditions.checkNotNull(builder.sku);
-        Preconditions.checkNotNull(builder.price);
-        Preconditions.checkNotNull(builder.quantity);
-        Preconditions.checkArgument(!builder.itemId.isEmpty(), "itemId cannot be empty");
-        Preconditions.checkArgument(!builder.sku.isEmpty(), "sku cannot be empty");
+        Objects.requireNonNull(builder.itemId);
+        Objects.requireNonNull(builder.sku);
+        Objects.requireNonNull(builder.price);
+        Objects.requireNonNull(builder.quantity);
+        if (builder.itemId.isEmpty()) {
+            throw new IllegalArgumentException("itemId cannot be empty");
+        }
+        if (builder.sku.isEmpty()) {
+            throw new IllegalArgumentException("sku cannot be empty");
+        }
 
         this.itemId = builder.itemId;
         this.sku = builder.sku;

src/main/java/com/snowplowanalytics/snowplow/tracker/events/PageView.java

@@ -12,14 +12,13 @@
  */
 package com.snowplowanalytics.snowplow.tracker.events;
 
-// Google
-import com.google.common.base.Preconditions;
-
 // This library
 import com.snowplowanalytics.snowplow.tracker.constants.Parameter;
 import com.snowplowanalytics.snowplow.tracker.constants.Constants;
 import com.snowplowanalytics.snowplow.tracker.payload.TrackerPayload;
 
+import java.util.Objects;
+
 /**
  * Constructs a PageView event object.
  *
@@ -90,8 +89,10 @@ protected PageView(Builder<?> builder) {
         super(builder);
 
         // Precondition checks
-        Preconditions.checkNotNull(builder.pageUrl);
-        Preconditions.checkArgument(!builder.pageUrl.isEmpty(), "pageUrl cannot be empty");
+        Objects.requireNonNull(builder.pageUrl);
+        if (builder.pageUrl.isEmpty()) {
+            throw new IllegalArgumentException("pageUrl cannot be empty");
+        }
 
         this.pageUrl = builder.pageUrl;
         this.pageTitle = builder.pageTitle;

src/main/java/com/snowplowanalytics/snowplow/tracker/events/ScreenView.java

@@ -12,8 +12,6 @@
  */
 package com.snowplowanalytics.snowplow.tracker.events;
 
-import com.google.common.base.Preconditions;
-
 import com.snowplowanalytics.snowplow.tracker.constants.Parameter;
 import com.snowplowanalytics.snowplow.tracker.constants.Constants;
 import com.snowplowanalytics.snowplow.tracker.payload.SelfDescribingJson;
@@ -77,7 +75,9 @@ protected ScreenView(Builder<?> builder) {
         super(builder);
 
         // Precondition checks
-        Preconditions.checkArgument(builder.name != null || builder.id != null);
+        if (builder.name == null || builder.id == null) {
+            throw new IllegalArgumentException();
+        }
 
         this.name = builder.name;
         this.id = builder.id;

src/main/java/com/snowplowanalytics/snowplow/tracker/events/SelfDescribing.java

@@ -12,15 +12,14 @@
  */
 package com.snowplowanalytics.snowplow.tracker.events;
 
-// Google
-import com.google.common.base.Preconditions;
-
 // This library
 import com.snowplowanalytics.snowplow.tracker.constants.Parameter;
 import com.snowplowanalytics.snowplow.tracker.constants.Constants;
 import com.snowplowanalytics.snowplow.tracker.payload.SelfDescribingJson;
 import com.snowplowanalytics.snowplow.tracker.payload.TrackerPayload;
 
+import java.util.Objects;
+
 /**
  * Constructs a SelfDescribing event object.
  *
@@ -70,7 +69,7 @@ protected SelfDescribing(Builder<?> builder) {
         super(builder);
 
         // Precondition checks
-        Preconditions.checkNotNull(builder.eventData);
+        Objects.requireNonNull(builder.eventData);
 
         this.eventData = builder.eventData;
     }