[java] Support templated servers

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaClientCodegen.java

@@ -285,6 +285,8 @@ else if (MICROPROFILE.equals(getLibrary())) {
         writeOptional(outputFolder, new SupportingFile("manifest.mustache", projectFolder, "AndroidManifest.xml"));
         supportingFiles.add(new SupportingFile("travis.mustache", "", ".travis.yml"));
         supportingFiles.add(new SupportingFile("ApiClient.mustache", invokerFolder, "ApiClient.java"));
+        supportingFiles.add(new SupportingFile("ServerConfiguration.mustache", invokerFolder, "ServerConfiguration.java"));
+        supportingFiles.add(new SupportingFile("ServerVariable.mustache", invokerFolder, "ServerVariable.java"));
         if (!(RESTTEMPLATE.equals(getLibrary()) || REST_ASSURED.equals(getLibrary()) || NATIVE.equals(getLibrary()) || MICROPROFILE.equals(getLibrary()))) {
             supportingFiles.add(new SupportingFile("StringUtil.mustache", invokerFolder, "StringUtil.java"));
         }

modules/openapi-generator/src/main/resources/Java/ApiClient.mustache

@@ -38,7 +38,9 @@ import java.util.Collections;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.TimeZone;
@@ -54,6 +56,8 @@ import {{invokerPackage}}.auth.Authentication;
 import {{invokerPackage}}.auth.HttpBasicAuth;
 import {{invokerPackage}}.auth.HttpBearerAuth;
 import {{invokerPackage}}.auth.ApiKeyAuth;
+import {{invokerPackage}}.ServerConfiguration;
+import {{invokerPackage}}.ServerVariable;
 {{#hasOAuthMethods}}
 import {{invokerPackage}}.auth.OAuth;
 {{/hasOAuthMethods}}
@@ -63,6 +67,33 @@ public class ApiClient {
   private Map<String, String> defaultHeaderMap = new HashMap<String, String>();
   private Map<String, String> defaultCookieMap = new HashMap<String, String>();
   private String basePath = "{{{basePath}}}";
+  protected List<ServerConfiguration> servers = new ArrayList<ServerConfiguration>({{#servers}}{{#-first}}Arrays.asList(
+{{/-first}}    new ServerConfiguration(
+      "{{{url}}}",
+      "{{{description}}}{{^description}}No description provided{{/description}}",
+      new HashMap<String, ServerVariable>(){{#variables}}{{#-first}} {{
+{{/-first}}        put("{{{name}}}", new ServerVariable(
+          "{{{description}}}{{^description}}No description provided{{/description}}",
+          "{{{defaultValue}}}",
+          new HashSet<String>(
+          {{#enumValues}}
+          {{#-first}}
+            Arrays.asList(
+          {{/-first}}
+              "{{{.}}}"{{^-last}},{{/-last}}
+          {{#-last}}
+            )
+          {{/-last}}
+          {{/enumValues}}
+          )
+        ));
+      {{#-last}}
+      }}{{/-last}}{{/variables}}
+    ){{^-last}},{{/-last}}
+  {{#-last}}
+  ){{/-last}}{{/servers}});
+  protected Integer serverIndex = 0;
+  protected Map<String, String> serverVariables = null;
   private boolean debugging = false;
   private int connectionTimeout = 0;
 
@@ -177,6 +208,33 @@ public class ApiClient {
     return this;
   }
 
+  public List<ServerConfiguration> getServers() {
+    return servers;
+  }
+
+  public ApiClient setServers(List<ServerConfiguration> servers) {
+    this.servers = servers;
+    return this;
+  }
+
+  public Integer getServerIndex() {
+    return serverIndex;
+  }
+
+  public ApiClient setServerIndex(Integer serverIndex) {
+    this.serverIndex = serverIndex;
+    return this;
+  }
+
+  public Map<String, String> getServerVariables() {
+    return serverVariables;
+  }
+
+  public ApiClient setServerVariables(Map<String, String> serverVariables) {
+    this.serverVariables = serverVariables;
+    return this;
+  }
+
   /**
    * Gets the status code of the previous request
    * @return Status code
@@ -252,7 +310,7 @@ public class ApiClient {
     }
     throw new RuntimeException("No API key authentication configured!");
   }
-  
+
   /**
    * Helper method to set API key prefix for the first API key authentication.
    * @param apiKeyPrefix API key prefix
@@ -626,8 +684,20 @@ public class ApiClient {
    * @return The full URL
    */
   private String buildUrl(String path, List<Pair> queryParams, List<Pair> collectionQueryParams) {
+    String baseURL;
+    if (serverIndex != null) {
+      if (index < 0 || index >= servers.size()) {
+        throw new ArrayIndexOutOfBoundsException(String.format(
+          "Invalid index %d when selecting the host settings. Must be less than %d", index, servers.size()
+        ));
+      }
+      baseURL = servers.get(serverIndex).URL(serverVariables);
+    } else {
+      baseURL = basePath;
+    }
+
     final StringBuilder url = new StringBuilder();
-    url.append(basePath).append(path);
+    url.append(baseURL).append(path);
 
     if (queryParams != null && !queryParams.isEmpty()) {
       // support (constant) query string in `path`, e.g. "/posts?draft=1"

modules/openapi-generator/src/main/resources/Java/ServerConfiguration.mustache

@@ -0,0 +1,60 @@
+package {{invokerPackage}};
+
+import java.util.Map;
+
+import com.datadog.api.v1.client.ServerVariable;
+
+/**
+ * Representing a Server configuration.
+ */
+public class ServerConfiguration {
+    public String URL;
+    public String description;
+    public Map<String, ServerVariable> variables;
+
+    /**
+     * @param A URL to the target host.
+     * @param description A describtion of the host designated by the URL.
+     * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
+     */
+    public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
+        this.URL = URL;
+        this.description = description;
+        this.variables = variables;
+    }
+
+    /**
+     * Format URL template using given variables.
+     *
+     * @param variables A map between a variable name and its value.
+     * @return Formatted URL.
+     */
+    public String URL(Map<String, String> variables) {
+        String url = this.URL;
+
+        // go through variables and replace placeholders
+        for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
+            String name = variable.getKey();
+            ServerVariable serverVariable = variable.getValue();
+            String value = serverVariable.defaultValue;
+
+            if (variables != null && variables.containsKey(name)) {
+                value = variables.get(name);
+                if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
+                    throw new RuntimeException("The variable " + name + " in the server URL has invalid value " + value + ".");
+                }
+            }
+            url = url.replaceAll("\\{" + name + "\\}", value);
+        }
+        return url;
+    }
+
+    /**
+     * Format URL template using default server variables.
+     *
+     * @return Formatted URL.
+     */
+    public String URL() {
+        return URL(null);
+    }
+}

modules/openapi-generator/src/main/resources/Java/ServerVariable.mustache

@@ -0,0 +1,23 @@
+package {{invokerPackage}};
+
+import java.util.HashSet;
+
+/**
+ * Representing a Server Variable for server URL template substitution.
+ */
+public class ServerVariable {
+    public String description;
+    public String defaultValue;
+    public HashSet<String> enumValues = null;
+
+    /**
+     * @param description A description for the server variable.
+     * @param defaultValue The default value to use for substitution.
+     * @param enumValues An enumeration of string values to be used if the substitution options are from a limited set.
+     */
+    public ServerVariable(String description, String defaultValue, HashSet<String> enumValues) {
+        this.description = description;
+        this.defaultValue = defaultValue;
+        this.enumValues = enumValues;
+    }
+}