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jamesmorganjamesmorgan
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Majour Refactor and README update with details
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‎README

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‎README.md

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## Dynamic Property Loader ##
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### Example Annotation Usage ###
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<pre>
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@ReloadableProperty("dynamicProperty.longValue")
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private long primitiveWithDefaultValue = 55;
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@ReloadableProperty("dynamicProperty.substitutionValue")
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private String stringProperty;
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</pre>
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### Example Properties File ###
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<pre>
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dynamicProperty.longValue=12345
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dynamicProperty.substitutionProperty=${dynamicProperty.substitutionValue}
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</pre>
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### Example Spring XML Configuration ###
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* See _src/main/resources/spring-reloadableProperties.xml_ for example configuration
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* All main components can be extended or replaced if required
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### How it Works ###
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When the spring Application Context is started an implementation of Springs PropertySourcesPlaceholderConfigurer is instantiated to perform additional logic when loading and setting values from a given set of properties files. (see:ReadablePropertySourcesPlaceholderConfigurer.class)
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During the time of ApplicationContext start also a new instance of InstantiationAwareBeanPostProcessorAdapter.class is created that allows post bean processing.
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Google Guava is used to implement a simple Publish & Subscribe (Pub-Sub) Pattern so that beans can be updated once created, i.e. a bean can subscribe to events. (see: EventBus)
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EventBus was chosen as it is a very easy and simplistic way to implement loosely couple object structure. (see: blog)
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When each properties file resource is loaded a FileWatch.class (see:FaileWatch.class) is started and attached to the given resource, reporting on any java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY events from the host operating system
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When an ENTRY_MODIFY event is fired firstly the resource changed is checked for property value changes then any bean subscribing to changes to the modified property has the specified field value updated with the new property
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### Tests ###
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A set of integration and unit tests can be found in _src/test/java_ (tests) & _src/test/resources_ (test resources)
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### TODO (Unfinished) ###
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* Assign a new thread to each resource directory specified (see: FileWatcherUnitTest.class for failing test @Ignore)
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### Why? ###
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* Useful for web applications which often need configuration changes but you don't always want to restart the application before new properties are used.
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* Can be used to define several layers of properties which can aid in defining multiple application configurations e.g sandbox/development/testing/production.
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* A pet project of mine I have been intending to implement/test for a while
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* A test of the new Java 7 WatchService API
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* Another dive in Spring & general investigation of Google Guava's EventBus, a class which I believe is the extremely useful and easy to use
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* The project is aimed to be open to modification if required
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* Sample testing tools (CountDownLatch, Hamcrest-1.3, JMock-2.6.0-RC2)
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### Future Changes ###
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* Ability to use Spring Expression language to map properties files
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* Support for Java 7 Data and Time classes
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* Add properties source of Database not just properties files
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### Supported Property Type Conversions Available ###
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* Joda Time Library (2.1) - [link](http://joda-time.sourceforge.net/)
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* LocalDate.class
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* LocalTime.class
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* LocalDateTime.class
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* Period.class
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* Spring Supported (3.1.2-RELEASE)
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* String.class
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* boolean.class, Boolean.class
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* byte.class, Byte.class
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* char.class, Character.class
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* short.class, Short.class
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* int.class, Integer.class
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* long.class, Long.class
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* float.class, Float.class
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* double.class, Double.class
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### Dependencies ###
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#### Core ####
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* Java 7 SDK
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* Spring (3.1.2-RELEASE)
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* Google Guava (12.0)
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#### Logging ####
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* logback (1.0.6)
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* slf4j (1.6.4)
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#### Testing ####
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* juint (4.10)
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* jmock (2.6.0-RC2)
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* hamcrest-all (1.3)
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* spring-test (3.1.2-RELEASE)

‎pom.xml

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<version>0.0.1-SNAPSHOT</version>
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<properties>
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<spring.version>3.1.1.RELEASE</spring.version>
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<spring.version>3.1.2.RELEASE</spring.version>
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</properties>
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<dependencies>
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<artifactId>spring-context</artifactId>
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<version>${spring.version}</version>
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</dependency>
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<dependency>
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<groupId>org.springframework</groupId>
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<artifactId>spring-expression</artifactId>
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<version>${spring.version}</version>
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</dependency>
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<dependency>
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<groupId>org.springframework</groupId>
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<artifactId>spring-core</artifactId>
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<version>${spring.version}</version>
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</dependency>
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<dependency>
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<groupId>org.springframework</groupId>
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<artifactId>spring-beans</artifactId>
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<version>${spring.version}</version>
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</dependency>
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<!-- TEST -->
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<dependency>
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<dependency>
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<groupId>org.springframework</groupId>
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<artifactId>spring-test</artifactId>
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<version>3.1.2.RELEASE</version>
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<version>${spring.version}</version>
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<scope>test</scope>
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</dependency>
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‎src/main/java/com/morgan/design/properties/bean/PropertyModifiedEvent.java

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private final Object oldValue;
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private final Object newValue;
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public PropertyModifiedEvent(String propertyName, Object oldValue, Object newValue) {
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public PropertyModifiedEvent(final String propertyName, final Object oldValue, final Object newValue) {
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this.propertyName = propertyName;
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this.oldValue = oldValue;
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this.newValue = newValue;
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public Object getNewValue() {
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return this.newValue;
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}
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@Override
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public int hashCode() {
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return Objects.hashCode(this.propertyName, this.oldValue, this.newValue);
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}
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@Override
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public boolean equals(Object object) {
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public boolean equals(final Object object) {
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if (object instanceof PropertyModifiedEvent) {
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PropertyModifiedEvent that = (PropertyModifiedEvent) object;
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final PropertyModifiedEvent that = (PropertyModifiedEvent) object;
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return Objects.equal(this.propertyName, that.propertyName) && Objects.equal(this.oldValue, that.oldValue)
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&& Objects.equal(this.newValue, that.newValue);
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}

‎src/main/java/com/morgan/design/properties/internal/GuavaPropertyChangedEventNotifier.java renamed to ‎src/main/java/com/morgan/design/properties/event/GuavaPropertyChangedEventNotifier.java

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package com.morgan.design.properties.internal;
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package com.morgan.design.properties.event;
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import org.springframework.beans.factory.annotation.Autowired;
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import org.springframework.beans.factory.annotation.Qualifier;
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import org.springframework.stereotype.Component;
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import com.google.common.eventbus.EventBus;
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import com.morgan.design.properties.bean.PropertyModifiedEvent;
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import com.morgan.design.properties.internal.ReloadablePropertyPostProcessor;
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@Component
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public class GuavaPropertyChangedEventNotifier implements PropertyChangedEventNotifier {

‎src/main/java/com/morgan/design/properties/internal/PropertyChangedEventNotifier.java renamed to ‎src/main/java/com/morgan/design/properties/event/PropertyChangedEventNotifier.java

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package com.morgan.design.properties.internal;
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package com.morgan.design.properties.event;
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import com.morgan.design.properties.bean.PropertyModifiedEvent;
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import com.morgan.design.properties.internal.ReloadablePropertyPostProcessor;
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public interface PropertyChangedEventNotifier {
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‎src/main/java/com/morgan/design/properties/internal/FileWatcher.java

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import static java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY;
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import java.io.IOException;
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import java.nio.file.FileSystems;
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import java.nio.file.Path;
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import java.nio.file.Paths;
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private final Resource[] locations;
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private final EventPublisher eventPublisher;
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public FileWatcher(final Resource[] locations, final EventPublisher eventPublisher) {
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private boolean exit;
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private WatchService watchService;
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public FileWatcher(final Resource[] locations, final EventPublisher eventPublisher) throws IOException {
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this.locations = locations;
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this.eventPublisher = eventPublisher;
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this.exit = false;
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this.watchService = FileSystems.getDefault()
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.newWatchService();
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}
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@Override
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public void run() {
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while (true) {
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while (doNotExit()) {
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for (final Resource resource : this.locations) {
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try {
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final Path path = Paths.get(resource.getFile()
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.getParentFile()
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.toURI());
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final WatchService watchService = FileSystems.getDefault()
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.newWatchService();
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final WatchKey basePathWatchKey = path.register(watchService, ENTRY_MODIFY);
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final WatchKey basePathWatchKey = path.register(this.watchService, ENTRY_MODIFY);
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final String resourceName = resource.getFilename();
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try {
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final WatchKey watchKey = watchService.take(); // Await modification
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final WatchKey watchKey = this.watchService.take(); // Await modification
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for (final WatchEvent<?> event : basePathWatchKey.pollEvents()) {
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final Path watchedPath = (Path) watchKey.watchable();
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}
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catch (final Exception e) {
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log.error("Exception thrown when watching resources, fileName: " + resource.getFilename(), e);
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stop();
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}
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}
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}
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}
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public void stop() {
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try {
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log.debug("Stopping file watcher");
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this.watchService.close();
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}
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catch (final IOException e) {
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log.error("Unable to stop file watcher", e);
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}
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this.exit = true;
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}
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private boolean doNotExit() {
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return !this.exit;
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}
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public boolean isRunning() {
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return this.exit == false;
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}
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private boolean isSameTargetFile(final String resourceName, final Path target) {
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return target.getFileName()
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.toString()

‎src/main/java/com/morgan/design/properties/internal/ReadablePropertySourcesPlaceholderConfigurer.java

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import org.springframework.core.io.support.PropertiesLoaderUtils;
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import com.morgan.design.properties.bean.PropertyModifiedEvent;
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import com.morgan.design.properties.event.PropertyChangedEventNotifier;
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import com.morgan.design.properties.internal.FileWatcher.EventPublisher;
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import com.morgan.design.properties.resolver.PropertyResolver;
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/**
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* Specialisation of {@link PropertySourcesPlaceholderConfigurer} that can react to changes in the resources specified. The watching process does not start by
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if (null == this.eventNotifier) {
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throw new BeanInitializationException("Event bus not setup, you should not be calling this method...!");
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}
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// Here we actually create and set a FileWatcher to monitor the given locations
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Executors.newSingleThreadExecutor()
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.execute(new FileWatcher(this.locations, this));
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try {
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// Here we actually create and set a FileWatcher to monitor the given locations
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Executors.newSingleThreadExecutor()
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.execute(new FileWatcher(this.locations, this));
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}
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catch (final IOException e) {
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log.error("Unable to start properties file watcher", e);
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}
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}
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public Object resolveProperty(final Object property) {

‎src/main/java/com/morgan/design/properties/internal/ReloadablePropertyPostProcessor.java

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import com.morgan.design.properties.bean.BeanPropertyHolder;
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import com.morgan.design.properties.bean.PropertyModifiedEvent;
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import com.morgan.design.properties.conversion.PropertyConversionService;
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import com.morgan.design.properties.event.PropertyChangedEventNotifier;
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/**
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* <p>
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}
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/**
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* Utility method to registers the class for receiving events about property files being changed, setting up bean re-injection once triggered.
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* Utility method to register the class for receiving events about property files being changed, setting up bean re-injection once triggered.
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*/
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public final void registerPropertyReloader() {
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// Setup Guava event bus listener

‎src/main/java/com/morgan/design/properties/internal/PropertyResolver.java renamed to ‎src/main/java/com/morgan/design/properties/resolver/PropertyResolver.java

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package com.morgan.design.properties.internal;
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package com.morgan.design.properties.resolver;
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/**
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* Interface to be apply any special property resolution techniques on the given object, see {@link SubstitutingPropertyResolver} for default implementation

‎src/main/java/com/morgan/design/properties/internal/SubstitutingPropertyResolver.java renamed to ‎src/main/java/com/morgan/design/properties/resolver/SubstitutingPropertyResolver.java

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package com.morgan.design.properties.internal;
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package com.morgan.design.properties.resolver;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;

‎src/test/resources/spring/spring-defaultConfiguration.xml renamed to ‎src/main/resources/spring/spring-defaultConfiguration.xml

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id="conversionService" />
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<bean
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class="com.morgan.design.properties.internal.GuavaPropertyChangedEventNotifier"
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class="com.morgan.design.properties.event.GuavaPropertyChangedEventNotifier"
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autowire="constructor" id="eventNotifier">
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<constructor-arg ref="propertiesEventBus" />
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</bean>
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<bean
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class="com.morgan.design.properties.internal.SubstitutingPropertyResolver"
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class="com.morgan.design.properties.resolver.SubstitutingPropertyResolver"
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id="propertyResolver" />
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</beans>

‎src/main/resources/spring/spring-reloadableProperties.xml

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http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
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">
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<!-- Define event bus for use with GuavaPropertyChangedEventNotifier -->
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<bean class="com.google.common.eventbus.EventBus" id="propertiesEventBus" />
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<import resource="classpath:/spring/spring-defaultConfiguration.xml" />
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<bean class="com.morgan.design.properties.conversion.DefaultPropertyConversionService" id="conversionService" />
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<bean class="com.morgan.design.properties.internal.GuavaPropertyChangedEventNotifier" autowire="constructor" id="eventNotifier">
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<constructor-arg ref="propertiesEventBus" />
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</bean>
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<bean class="com.morgan.design.properties.internal.SubstitutingPropertyResolver" id="propertyResolver" />
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<bean class="com.morgan.design.properties.internal.ReloadablePropertyPostProcessor">
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<bean
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class="com.morgan.design.properties.internal.ReloadablePropertyPostProcessor">
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<constructor-arg ref="propertyConfigurator" />
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<constructor-arg ref="eventNotifier" />
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<constructor-arg ref="conversionService" />
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</bean>
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<bean id="readablePlaceholder" class="com.morgan.design.properties.internal.ReadablePropertySourcesPlaceholderConfigurer">
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<bean id="propertyConfigurator"
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class="com.morgan.design.properties.internal.ReadablePropertySourcesPlaceholderConfigurer">
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<property name="ignoreUnresolvablePlaceholders" value="false" />
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<property name="ignoreResourceNotFound" value="true" />
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<constructor-arg ref="eventNotifier" />
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<constructor-arg ref="propertyResolver" />
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<property name="locations">
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<list>
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<value>classpath*:META-INF/*.properties</value>

‎src/test/java/com/morgan/design/properties/internal/GuavaPropertyChangedEventNotifierUnitTest.java renamed to ‎src/test/java/com/morgan/design/properties/event/GuavaPropertyChangedEventNotifierUnitTest.java

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package com.morgan.design.properties.internal;
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package com.morgan.design.properties.event;
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import org.jmock.Expectations;
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import org.jmock.Mockery;
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import com.google.common.eventbus.EventBus;
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import com.morgan.design.properties.bean.PropertyModifiedEvent;
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import com.morgan.design.properties.internal.ReloadablePropertyPostProcessor;
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@RunWith(JMock.class)
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@SuppressWarnings("unqualified-field-access")

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