001package io.dinject;
002
003import java.lang.annotation.ElementType;
004import java.lang.annotation.Retention;
005import java.lang.annotation.RetentionPolicy;
006import java.lang.annotation.Target;
007
008/**
009 * A singleton bean that has methods marked with the <code>@Bean</code> annotation.
010 * <p>
011 * Factory beans allow us to build beans using logic in methods. These methods for example
012 * often use environment variables and system properties into account when building the bean.
013 * </p>
014 * <p>
015 * Relative to <code>javax.inject.Provider</code> Factory and Bean provide a more flexible
016 * approach that allows dependencies on the method (as method parameters) as well as multiple
017 * methods on the single factory bean. The expectation is that we tend to use Factory and Bean
018 * rather than Provider.
019 * </p>
020 *
021 * <pre>{@code
022 *
023 * @Factory
024 * class Configuration {
025 *
026 *   private final StartConfig startConfig;
027 *
028 *   @Inject
029 *   Configuration(StartConfig startConfig) {
030 *     this.startConfig = startConfig;
031 *   }
032 *
033 *   @Bean
034 *   Foo buildFoo() {
035 *     ...
036 *     return new Foo(...);
037 *   }
038 *
039 *   @Bean
040 *   Bar buildBar(Foo foo, Bazz bazz) {
041 *     ...
042 *     return new Bar(...);
043 *   }
044 * }
045 * }</pre>
046 */
047@Target(ElementType.TYPE)
048@Retention(RetentionPolicy.RUNTIME)
049public @interface Factory {
050}