build(java): Upgrade to java 11

README.md

@@ -61,10 +61,31 @@ For example:
 <dependency>
     <groupId>software.amazon.nio.s3</groupId>
     <artifactId>aws-java-nio-spi-for-s3</artifactId>
-    <version>1.2.4</version>
+    <version>2.0.0-dev</version>
 </dependency>
 ```
 
+```groovy
+    implementation("software.amazon.nio.s3:aws-java-nio-spi-for-s3:2.0.0-dev")
+```
+
+### Java compatibility
+| Library version | Java   |
+|-----------------|--------|
+| <= 1.2.1        | \>=  8 |
+| \>= 2.x.x       | \>= 11 |
+
+Versions 1.2.2 until 2.x.x are compatible with java 8 and above,
+but will need to exclude logback dependency if using with java 8:
+```groovy
+implementation("software.amazon.nio.s3:aws-java-nio-spi-for-s3:1.2.2") {
+    exclude group: 'ch.qos.logback', module: 'logback-core'
+    exclude group: 'ch.qos.logback', module: 'logback-classic'
+}
+implementation("ch.qos.logback:logback-classic:1.3.11") // 1.3.x is still compatible with java 8
+implementation("ch.qos.logback:logback-core:1.3.11")
+```
+
 ## AWS Credentials
 
 This library will perform all actions using credentials according to the AWS SDK for Java [default credential provider
@@ -286,14 +307,14 @@ to `/foo/baa`.
 
 ## Building this library
 
-The library uses the gradle build system and targets Java 1.8 to allow it to be used in many contexts. To build you can simply run:
+The library uses the gradle build system and targets Java 11 to allow it to be used in many contexts. To build you can simply run:
 
 ```shell
 ./gradlew build
 ```
 
 This will run all unit tests and then generate a jar file in `libs` with the name `s3fs-spi-<version>.jar`. Note that
-although the compiled JAR targets Java 1.8 a later version of the JDK may be needed to run Gradle itself.
+although the compiled JAR targets Java 11 a later version of the JDK may be needed to run Gradle itself.
 
 ### Shadowed Jar with dependencies
 
@@ -322,7 +343,7 @@ found at `build/reports/jacoco/test/html/index.html`
 We encourage community contributions via pull requests. Please refer to our [code of conduct](./CODE_OF_CONDUCT.md) and
 [contributing](./CONTRIBUTING.md) for guidance.
 
-Code must compile to JDK 1.8 compatible bytecode. Matching unit tests are required for new features and fixes.
+Code must compile to JDK 11 compatible bytecode. Matching unit tests are required for new features and fixes.
 
 ### Contributing Unit Tests
 

build.gradle

@@ -25,19 +25,19 @@ group = 'software.amazon.nio.s3'
 archivesBaseName = 'nio-spi-for-s3'
 version = '2.0.0-dev'
 
-apply plugin: 'java'
-sourceCompatibility = 1.8
-targetCompatibility = 1.8
-
-
 java {
     withSourcesJar()
     withJavadocJar()
 }
 
-compileJava {
-    // see https://docs.gradle.org/6.6/userguide/building_java_projects.html#sec:java_cross_compilation
-    options.release = 8
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(11)
+    }
+}
+
+tasks.withType(JavaCompile).configureEach {
+    options.release.set(11)
 }
 
 sourceSets {
@@ -58,8 +58,7 @@ dependencies {
     implementation 'org.slf4j:slf4j-api:2.0.9'
     implementation 'ch.qos.logback:logback-classic:1.4.11'
     implementation 'ch.qos.logback:logback-core:1.4.11'
-    // cannot use caffeine v3 because that requires java 11
-    implementation('com.github.ben-manes.caffeine:caffeine:2.9.3')
+    implementation 'com.github.ben-manes.caffeine:caffeine:3.1.8'
 
     examplesImplementation project
 }

src/main/java/software/amazon/nio/spi/s3/S3ClientProvider.java

@@ -35,7 +35,6 @@
 import software.amazon.awssdk.services.s3.model.HeadBucketResponse;
 import software.amazon.awssdk.services.s3.model.S3Exception;
 import software.amazon.nio.spi.s3.config.S3NioSpiConfiguration;
-import static software.amazon.nio.spi.s3.util.StringUtils.isBlank;
 
 /**
  * Factory/builder class that creates sync and async S3 clients. It also provides
@@ -179,7 +178,7 @@ protected S3Client generateClient (String bucketName, S3Client locationClient) {
         logger.debug("generating client for bucket: '{}'", bucketName);
         S3Client bucketSpecificClient = null;
 
-        if ((configuration.getEndpoint() == null) || isBlank(configuration.getEndpoint())) {
+        if ((configuration.getEndpoint() == null) || configuration.getEndpoint().isBlank()) {
             //
             // we try to locate a bucket only if no endpoint is provided, which
             // means we are dealing with AWS S3 buckets
@@ -239,7 +238,7 @@ protected S3AsyncClient generateAsyncClient (String bucketName, S3Client locatio
         logger.debug("generating asynchronous client for bucket: '{}'", bucketName);
         S3AsyncClient bucketSpecificClient = null;
 
-        if ((configuration.getEndpoint() == null) || isBlank(configuration.getEndpoint())) {
+        if ((configuration.getEndpoint() == null) || configuration.getEndpoint().isBlank()) {
             //
             // we try to locate a bucket only if no endpoint is provided, which
             // means we are dealing with AWS S3 buckets
@@ -302,7 +301,7 @@ private S3Client clientForRegion(String regionName) {
                 )
             );
 
-        if (!isBlank(endpoint)) {
+        if (!endpoint.isBlank()) {
             clientBuilder.endpointOverride(URI.create(configuration.getEndpointProtocol() + "://" + endpoint));
         }
 
@@ -321,7 +320,7 @@ private S3AsyncClient asyncClientForRegion(String regionName) {
 
         logger.debug("bucket region is: '{}'", region.id());
 
-        if (!isBlank(endpoint)) {
+        if (!endpoint.isBlank()) {
             asyncClientBuilder.endpointOverride(URI.create(configuration.getEndpointProtocol() + "://" + endpoint));
         }
 

src/main/java/software/amazon/nio/spi/s3/config/S3NioSpiConfiguration.java

@@ -177,7 +177,7 @@ public S3NioSpiConfiguration withEndpoint(String endpoint) {
         }
         endpoint = endpoint.trim();
 
-        if ((endpoint.length() > 0) && !ENDPOINT_REGEXP.matcher(endpoint).matches()) {
+        if (!endpoint.isEmpty() && !ENDPOINT_REGEXP.matcher(endpoint).matches()) {
             throw new IllegalArgumentException(
                 String.format("endpoint '%s' does not match format host:port where port is a number", endpoint)
             );
@@ -211,7 +211,7 @@ public S3NioSpiConfiguration withEndpointProtocol(String protocol) {
      * @return this instance
      */
     public S3NioSpiConfiguration withRegion(String region) {
-        if ((region == null) || StringUtils.isBlank(region)) {
+        if ((region == null) || region.isBlank()) {
             remove(AWS_REGION_PROPERTY);
         } else {
             put(AWS_REGION_PROPERTY, region.trim());

src/main/java/software/amazon/nio/spi/s3/util/StringUtils.java

@@ -34,22 +34,4 @@ public static String joinFrom(String separator, String[] elements, int startAt)
         return sj.toString();
     }
 
-    /**
-     * Like Java 11's String.isBlank(): it returns true if the string is empty or
-     * contains only white space codepoints, otherwise false.
-     *
-     * @param s the string to check
-     *
-     * @return true if the string is empty or contains only white space codepoints, otherwise false
-     *
-     * TODO: to replace with Java11's isBlank when moving away from Java8
-     */
-    public static boolean isBlank(final String s) {
-        for (int i=0; i<s.length(); ++i) {
-            if (!Character.isWhitespace(s.charAt(i))) {
-                return false;
-            }
-        }
-        return true;
-    }
 }