#10 - ENH: Add HttpClientContext.create() method to obtain a http client implementation

Author: rbygrave

client/src/main/java/io/avaje/http/client/DHttpClientContext.java

@@ -1,6 +1,7 @@
 package io.avaje.http.client;
 
 import java.io.IOException;
+import java.lang.reflect.Constructor;
 import java.net.http.HttpClient;
 import java.net.http.HttpHeaders;
 import java.net.http.HttpRequest;
@@ -33,6 +34,29 @@ class DHttpClientContext implements HttpClientContext {
     this.requestIntercept = intercept;
   }
 
+  @Override
+  @SuppressWarnings("unchecked")
+  public <T> T create(Class<T> clientInterface) {
+    if (!clientInterface.isInterface()) {
+      throw new IllegalArgumentException("API declarations must be interfaces.");
+    }
+    String implClassName = clientImplementationClassName(clientInterface);
+    try {
+      Class<?> serviceClass = Class.forName(implClassName);
+      Constructor<?> constructor = serviceClass.getConstructor(HttpClientContext.class);
+      Object service = constructor.newInstance(this);
+      return (T) service;
+    } catch (Exception e) {
+      throw new IllegalStateException("Failed to create http client service " + implClassName, e);
+    }
+  }
+
+  private <T> String clientImplementationClassName(Class<T> clientInterface) {
+    String packageName = clientInterface.getPackageName();
+    String simpleName = clientInterface.getSimpleName();
+    return packageName + ".httpclient." + simpleName + "$httpclient";
+  }
+
   @Override
   public HttpClientRequest request() {
     return new DHttpClientRequest(this, requestTimeout);

client/src/main/java/io/avaje/http/client/HttpClientContext.java

@@ -47,6 +47,15 @@ static HttpClientContext.Builder newBuilder() {
     return new DHttpClientContextBuilder();
   }
 
+  /**
+   * Return the http client API implementation.
+   *
+   * @param clientInterface A <code>@Client</code> interface with annotated API methods.
+   * @param <T>             The service type.
+   * @return The http client API implementation.
+   */
+  <T> T create(Class<T> clientInterface);
+
   /**
    * Create a new request.
    */

client/src/test/java/io/avaje/http/client/DHttpClientContextTest.java

@@ -1,5 +1,6 @@
 package io.avaje.http.client;
 
+import org.example.github.BasicClientInterface;
 import org.junit.jupiter.api.Test;
 
 import java.net.http.HttpClient;
@@ -11,6 +12,12 @@ class DHttpClientContextTest {
 
   private final DHttpClientContext context = new DHttpClientContext(null, null, null, null, null, null, null);
 
+  @Test
+  void create() {
+    BasicClientInterface client = context.create(BasicClientInterface.class);
+    assertThat(client).isNotNull();
+  }
+
   @Test
   void gzip_gzipDecode() {
 

client/src/test/java/org/example/github/BasicClientInterface.java

@@ -0,0 +1,14 @@
+package org.example.github;
+
+import io.avaje.http.api.Get;
+import io.avaje.http.api.Path;
+import io.avaje.http.client.HttpException;
+
+import java.util.List;
+
+@Path("/")
+public interface BasicClientInterface {
+
+  @Get("users/{user}/repos")
+  List<Repo> listRepos(String user, String other) throws HttpException;
+}

client/src/test/java/org/example/github/httpclient/BasicClientInterface$httpclient.java

@@ -0,0 +1,23 @@
+package org.example.github.httpclient;
+
+import io.avaje.http.client.HttpClientContext;
+import io.avaje.http.client.HttpException;
+import org.example.github.BasicClientInterface;
+import org.example.github.Repo;
+
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Placeholder for code generated by avaje-http-client-generator.
+ */
+public class BasicClientInterface$httpclient implements BasicClientInterface {
+
+  public BasicClientInterface$httpclient(HttpClientContext context) {
+
+  }
+  @Override
+  public List<Repo> listRepos(String user, String other) throws HttpException {
+    return Collections.emptyList();
+  }
+}