ClientBinding.java

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package org.glassfish.jersey.server;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import javax.ws.rs.core.Configuration;

/**
 * Meta-annotation that provides a facility for creating bindings between an {@link Uri @Uri}-injectable
 * {@link javax.ws.rs.client.WebTarget WebTarget} instances and clients (and their configurations) that are used to create
 * the injected web target instances.
 * <p>
 * Jersey refers to client instance configured using custom bound configurations as <em>managed clients</em>. As a first step,
 * when using a managed client in a server-side JAX-RS/Jersey application, a custom client binding annotation has to be
 * defined:
 * <pre>
 * @ClientBinding
 * public @interface <b>MyClient</b> { }
 * </pre>
 * This defines new {@code @MyClient} binding annotation which will be configured using a default {@link #configClass()
 * configuration class}, will {@link #inheritServerProviders() inherit all server-side providers} as well as will use a
 * default {@link #baseUri() base URI} to resolve relative {@link Uri @Uri} web target URI values.
 * </p>
 * <p>
 * Once a custom client binding annotation is defined, it can be used when {@link Uri injecting} new
 * {@code WebTarget} instances created by a managed client. To complete a binding between a manged client and an injected
 * web target instance, put the custom client binding annotation into the definition of an injected web target field or
 * parameter. For example:
 * <pre>
 * @Path("foo")
 * public class ManagedClientResource {
 *   @Uri("bar") <b>@MyClient</b>
 *   private WebTarget targetBar;
 *
 *   @GET
 *   @Path("bar")
 *   public String getBar() {
 *     return targetBar.request(MediaType.TEXT_PLAIN).get(String.class);
 *   }
 *
 *   @GET
 *   @Path("baz")
 *   public Response getBaz(@Uri("baz") <b>@MyClient</b> WebTarget targetBaz) {
 *     return targetB.request(MediaType.TEXT_PLAIN).get();
 *   }
 * }
 * </pre>
 * </p>
 * <p>
 * Often managed clients may require a more complex configuration, including specifying custom provider classes and instances
 * and setting custom properties. In such case it may be more convenient to provide a custom {@link Configuration}
 * implementation class and link it with the binding annotation:
 * <pre>
 * public class <b>MyClientConfig</b> implements Configuration {
 *   ... // configure provide
 * }
 *
 * @ClientBinding(configClass = <b>MyClientConfig</b>.class)
 * public @interface <b>MyClient</b> { }
 * </pre>
 * Note that the easiest way how to provide a custom client-side {@code Configuration} implementation in Jersey is to extend
 * the {@link org.glassfish.jersey.client.ClientConfig} class that provides reusable implementation of JAX-RS
 * {@link Configuration} as well as {@link javax.ws.rs.core.Configurable Configurable} APIs.
 * </p>
 * <p>
 * In case a managed client needs special properties, these properties can also be provided via custom {@code Configuration}
 * implementation class. Another way how to pass custom properties to a managed client configuration is to define the managed
 * client properties in the server configuration using a special
 * <tt><em><client.binding.annotation.FQN></em>.property.</tt> prefix. This can be either done programmatically,
 * for example:
 * <pre>
 * MyResourceConfig.property(
 *     "my.package.MyClient.property.<b>custom-client-property</b>", "custom-value");
 * </pre>
 * </p>
 * <p>
 * Or declaratively via {@code web.xml}:
 * <pre>
 * <init-param>
 *     <param-name>my.package.MyClient.property.<b>custom-client-property</b></param-name>
 *     <param-value>custom-value</param-value>
 * </init-param>
 * </pre>
 * Properties defined this way can be accessed from the proper managed client instances using the custom property names:
 * <pre>
 * Object value = customTarget.getConfiguration().getProperty("<b>custom-client-property</b>");
 * </pre>
 * Note that the technique of defining managed client properties via server-side configuration described above can be also used
 * to override the default property values defined programmatically in a custom configuration implementation class.
 * </p>
 *
 * @author Marek Potociar (marek.potociar at oracle.com)
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.ANNOTATION_TYPE)
@Documented
public @interface ClientBinding {
    /**
     * Define a configuration implementation class to be instantiated and used to configure bound web targets.
     * If not set, a default client-side configuration implementation class will be used.
     * <p>
     * Hard-coded value of this property may be overridden at deploy-time by providing a new value for a
     * <tt><em><client.binding.annotation.FQN></em>.configClass</tt> property.
     * </p>
     * <p>
     * For example:
     * <pre>
     * MyResourceConfig.property(
     *     "my.package.MyClient.configClass",
     *     "my.package.MyClientConfig");
     * </pre>
     * </p>
     * <p>
     * Or declaratively via {@code web.xml}:
     * <pre>
     * <init-param>
     *     <param-name>my.package.MyClient.configClass</param-name>
     *     <param-value>my.package.MyClientConfig</param-value>
     * </init-param>
     * </pre>
     * </p>
     */
    public Class<? extends Configuration> configClass() default Configuration.class;

    /**
     * Determine whether providers present in the server-side configuration should be inherited by the bound client
     * configuration ({@code true}) or not ({@code false}). By default the server-side providers are inherited, i.e.
     * the annotation property defaults to {@code true}.
     * <p>
     * Hard-coded value of this property may be overridden at deploy-time by providing a new value for a
     * <tt><em><client.binding.annotation.FQN></em>.inheritServerProviders</tt> property.
     * </p>
     * <p>
     * For example:
     * <pre>
     * MyResourceConfig.property(
     *     "my.package.MyClient.inheritServerProviders", false);
     * </pre>
     * </p>
     * <p>
     * Or declaratively via {@code web.xml}:
     * <pre>
     * <init-param>
     *     <param-name>my.package.MyClient.inheritServerProviders</param-name>
     *     <param-value>false</param-value>
     * </init-param>
     * </pre>
     * </p>
     */
    public boolean inheritServerProviders() default true;

    /**
     * Define a custom base URI for managed {@link javax.ws.rs.client.WebTarget WebTarget} instances injected using
     * {@link Uri @Uri} annotation with a relative web target URI value. By default, the base
     * URI is empty indicating that the current application base URI should be used.
     * <p>
     * Using a custom context root is useful in cases where the absolute URI of the target endpoint(s) is expected
     * to change on may vary over time. An typical scenarios include transition of the application from a test to
     * production environment, etc.
     * </p>
     * <p>
     * Hard-coded value of this property may be overridden at deploy-time by providing a new value for a
     * <tt><em><client.binding.annotation.FQN></em>.baseUri</tt> property.
     * </p>
     * <p>
     * For example:
     * <pre>
     * MyResourceConfig.property(
     *     "my.package.MyClient.baseUri", "http://jersey.java.net/examples/");
     * </pre>
     * </p>
     * <p>
     * Or declaratively via {@code web.xml}:
     * <pre>
     * <init-param>
     *     <param-name>my.package.MyClient.baseUri</param-name>
     *     <param-value>http://jersey.java.net/examples/</param-value>
     * </init-param>
     * </pre>
     * </p>
     */
    public String baseUri() default "";
}