Add command to display all library templates supported

for a specific language

README.md

@@ -116,6 +116,10 @@ OPTIONS
             client language to generate (maybe class name in classpath,
             required)
 
+        -L <library>, --library <library>
+            Library template (sub-template) to use. Run library-help -l {lang}
+            command for a list of supported libraries.
+
         -o <output directory>, --output <output directory>
             where to write the generated files (current dir by default)
 
@@ -128,7 +132,7 @@ OPTIONS
         -s , --skip-overwrite
             specifies if the existing files should be overwritten during 
             the generation 
- ```
+```
 
 You can then compile and run the client, as well as unit tests against it:
 
@@ -144,6 +148,23 @@ Other languages have petstore samples, too:
 ./bin/objc-petstore.sh
 ```
 
+Various library templates (sub-templates) might be available for a specific language. Running `library-help -l {lang}` will show all library templates supported.
+
+```
+java -jar modules/swagger-codegen-cli/target/swagger-codegen-cli.jar library-help -l java
+```
+
+Output
+
+```
+LIBRARY OPTIONS
+        <default>
+            HTTP client: Jersey client 1.18. JSON processing: Jackson 2.4.2
+
+        jersey2
+            HTTP client: Jersey client 2.6
+```
+
 ### Generating libraries from your server
 It's just as easy--just use the `-i` flag to point to either a server or file.
 

modules/swagger-codegen-cli/src/main/java/io/swagger/codegen/SwaggerCodegen.java

@@ -5,6 +5,7 @@ import io.airlift.airline.Help;
 import io.swagger.codegen.cmd.ConfigHelp;
 import io.swagger.codegen.cmd.Generate;
 import io.swagger.codegen.cmd.Langs;
+import io.swagger.codegen.cmd.LibraryHelp;
 import io.swagger.codegen.cmd.Meta;
 
 /**
@@ -29,7 +30,8 @@ public class SwaggerCodegen {
                         Meta.class,
                         Langs.class,
                         Help.class,
-                        ConfigHelp.class
+                        ConfigHelp.class,
+                        LibraryHelp.class
                 );
 
         builder.build().parse(args).run();

modules/swagger-codegen-cli/src/main/java/io/swagger/codegen/cmd/Generate.java

@@ -41,7 +41,8 @@ public class Generate implements Runnable {
     private String lang;
 
     @Option(name = {"-L", "--library"}, title = "library",
-            description = "library template (sub-template) to use")
+            description = "Library template (sub-template) to use. Run library-help -l {lang} " +
+            "command for a list of supported libraries.")
     private String library;
 
     @Option(name = {"-o", "--output"}, title = "output directory",

modules/swagger-codegen-cli/src/main/java/io/swagger/codegen/cmd/LibraryHelp.java

@@ -0,0 +1,55 @@
+package io.swagger.codegen.cmd;
+
+import io.airlift.airline.Command;
+import io.airlift.airline.Option;
+import io.swagger.codegen.CliOption;
+import io.swagger.codegen.CodegenConfig;
+
+import java.util.ServiceLoader;
+
+import static java.util.ServiceLoader.load;
+
+@Command(name = "library-help", description = "Library help for chosen lang")
+public class LibraryHelp implements Runnable {
+
+    @Option(name = {"-l", "--lang"}, title = "language", required = true,
+            description = "language to get library help for")
+    private String lang;
+
+    /**
+     * Tries to load config class with SPI first, then with class name directly from classpath
+     *
+     * @param name name of config, or full qualified class name in classpath
+     * @return config class
+     */
+    private static CodegenConfig forName(String name) {
+        ServiceLoader<CodegenConfig> loader = load(CodegenConfig.class);
+        for (CodegenConfig config : loader) {
+            if (config.getName().equals(name)) {
+                return config;
+            }
+        }
+
+        // else try to load directly
+        try {
+            return (CodegenConfig) Class.forName(name).newInstance();
+        } catch (Exception e) {
+            throw new RuntimeException("Can't load config class with name ".concat(name), e);
+        }
+    }
+
+    @Override
+    public void run() {
+        System.out.println();
+        CodegenConfig config = forName(lang);
+        System.out.println("LIBRARY OPTIONS");
+        for (String library : config.supportedLibraries().keySet()) {
+            String description = config.supportedLibraries().get(library);
+            if ("".equals(library))
+                library = "<default>";
+            System.out.println("\t" + library);
+            System.out.println("\t    " + description);
+            System.out.println();
+        }
+    }
+}

modules/swagger-codegen/src/main/java/io/swagger/codegen/CodegenConfig.java

@@ -109,6 +109,8 @@ public interface CodegenConfig {
 
     void setSkipOverwrite(boolean skipOverwrite);
 
+    Map<String, String> supportedLibraries();
+
     void setLibrary(String library);
 
     /**

modules/swagger-codegen/src/main/java/io/swagger/codegen/DefaultCodegen.java

@@ -81,6 +81,7 @@ public class DefaultCodegen {
     protected List<CliOption> cliOptions = new ArrayList<CliOption>();
     protected boolean skipOverwrite;
     protected boolean supportsInheritance = false;
+    protected Map<String, String> supportedLibraries = new HashMap<String, String>();
     protected String library = null;
 
     public List<CliOption> cliOptions() {
@@ -1389,7 +1390,16 @@ public class DefaultCodegen {
         this.skipOverwrite = skipOverwrite;
     }
 
+    /**
+     * All library templates supported.
+     */
+    public Map<String, String> supportedLibraries() {
+        return supportedLibraries;
+    }
+
     public void setLibrary(String library) {
+        if (library != null && !supportedLibraries.containsKey(library))
+            throw new RuntimeException("unknown library: " + library);
         this.library = library;
     }
 

modules/swagger-codegen/src/main/java/io/swagger/codegen/DefaultGenerator.java

@@ -266,7 +266,7 @@ public class DefaultGenerator extends AbstractGenerator implements Generator {
 
                 String templateFile = null;
                 String library = config.getLibrary();
-                if (library != null) {
+                if (library != null && !"".equals(library)) {
                     String libTemplateFile = config.templateDir() + File.separator +
                         "libraries" + File.separator + library + File.separator +
                         support.templateFile;

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/JavaClientCodegen.java

@@ -61,6 +61,9 @@ public class JavaClientCodegen extends DefaultCodegen implements CodegenConfig {
         cliOptions.add(new CliOption("artifactId", "artifactId in generated pom.xml"));
         cliOptions.add(new CliOption("artifactVersion", "artifact version in generated pom.xml"));
         cliOptions.add(new CliOption("sourceFolder", "source folder for generated code"));
+
+        supportedLibraries.put("", "HTTP client: Jersey client 1.18. JSON processing: Jackson 2.4.2");
+        supportedLibraries.put("jersey2", "HTTP client: Jersey client 2.6");
     }
 
     public CodegenType getTag() {