src/jdk.jlink/share/classes/jdk/tools/jlink/builder/DefaultImageBuilder.java

*** 128,151 ****
              }
          }
      }
  
      private final Path root;
      private final Path mdir;
      private final Set<String> modules = new HashSet<>();
      private String targetOsName;
  
      /**
       * Default image builder constructor.
       *
       * @param root The image root directory.
       * @throws IOException
       */
!     public DefaultImageBuilder(Path root) throws IOException {
!         Objects.requireNonNull(root);
! 
!         this.root = root;
          this.mdir = root.resolve("lib");
          Files.createDirectories(mdir);
      }
  
      @Override
--- 128,151 ----
              }
          }
      }
  
      private final Path root;
+     private final Map<String, String> launchers;
      private final Path mdir;
      private final Set<String> modules = new HashSet<>();
      private String targetOsName;
  
      /**
       * Default image builder constructor.
       *
       * @param root The image root directory.
       * @throws IOException
       */
!     public DefaultImageBuilder(Path root, Map<String, String> launchers) throws IOException {
!         this.root = Objects.requireNonNull(root);
!         this.launchers = Objects.requireNonNull(launchers);
          this.mdir = root.resolve("lib");
          Files.createDirectories(mdir);
      }
  
      @Override
*** 233,280 ****
              }
  
              // If native files are stripped completely, <root>/bin dir won't exist!
              // So, don't bother generating launcher scripts.
              if (Files.isDirectory(bin)) {
!                  prepareApplicationFiles(files, modules);
              }
          } catch (IOException ex) {
              throw new PluginException(ex);
          }
      }
  
      /**
       * Generates launcher scripts.
       *
       * @param imageContent The image content.
-      * @param modules The set of modules that the runtime image contains.
       * @throws IOException
       */
!     protected void prepareApplicationFiles(ResourcePool imageContent, Set<String> modules) throws IOException {
          // generate launch scripts for the modules with a main class
!         for (String module : modules) {
              String path = "/" + module + "/module-info.class";
              Optional<ResourcePoolEntry> res = imageContent.findEntry(path);
              if (!res.isPresent()) {
                  throw new IOException("module-info.class not found for " + module + " module");
              }
-             Optional<String> mainClass;
              ByteArrayInputStream stream = new ByteArrayInputStream(res.get().contentBytes());
!             mainClass = ModuleDescriptor.read(stream).mainClass();
!             if (mainClass.isPresent()) {
!                 Path cmd = root.resolve("bin").resolve(module);
                  // generate shell script for Unix platforms
                  StringBuilder sb = new StringBuilder();
                  sb.append("#!/bin/sh")
                          .append("\n");
                  sb.append("JLINK_VM_OPTIONS=")
                          .append("\n");
                  sb.append("DIR=`dirname $0`")
                          .append("\n");
                  sb.append("$DIR/java $JLINK_VM_OPTIONS -m ")
                          .append(module).append('/')
!                         .append(mainClass.get())
                          .append(" $@\n");
  
                  try (BufferedWriter writer = Files.newBufferedWriter(cmd,
                          StandardCharsets.ISO_8859_1,
                          StandardOpenOption.CREATE_NEW)) {
--- 233,302 ----
              }
  
              // If native files are stripped completely, <root>/bin dir won't exist!
              // So, don't bother generating launcher scripts.
              if (Files.isDirectory(bin)) {
!                  prepareApplicationFiles(files);
              }
          } catch (IOException ex) {
              throw new PluginException(ex);
          }
      }
  
      /**
       * Generates launcher scripts.
       *
       * @param imageContent The image content.
       * @throws IOException
       */
!     protected void prepareApplicationFiles(ResourcePool imageContent) throws IOException {
          // generate launch scripts for the modules with a main class
!         for (Map.Entry<String, String> entry : launchers.entrySet()) {
!             String launcherEntry = entry.getValue();
!             int slashIdx = launcherEntry.indexOf("/");
!             String module, mainClassName;
!             if (slashIdx == -1) {
!                 module = launcherEntry;
!                 mainClassName = null;
!             } else {
!                 module = launcherEntry.substring(0, slashIdx);
!                 assert !module.isEmpty();
!                 mainClassName = launcherEntry.substring(slashIdx + 1);
!                 assert !mainClassName.isEmpty();
!             }
! 
              String path = "/" + module + "/module-info.class";
              Optional<ResourcePoolEntry> res = imageContent.findEntry(path);
              if (!res.isPresent()) {
                  throw new IOException("module-info.class not found for " + module + " module");
              }
              ByteArrayInputStream stream = new ByteArrayInputStream(res.get().contentBytes());
!             Optional<String> mainClass = ModuleDescriptor.read(stream).mainClass();
!             if (mainClassName == null && mainClass.isPresent()) {
!                 mainClassName = mainClass.get();
!             }
! 
!             if (mainClassName != null) {
!                 // make sure main class exists!
!                 if (!imageContent.findEntry("/" + module + "/" +
!                         mainClassName.replace('.', '/') + ".class").isPresent()) {
!                     throw new RuntimeException(module + " does not have main class: " + mainClassName);
!                 }
! 
!                 String launcherFile = entry.getKey();
!                 Path cmd = root.resolve("bin").resolve(launcherFile);
                  // generate shell script for Unix platforms
                  StringBuilder sb = new StringBuilder();
                  sb.append("#!/bin/sh")
                          .append("\n");
                  sb.append("JLINK_VM_OPTIONS=")
                          .append("\n");
                  sb.append("DIR=`dirname $0`")
                          .append("\n");
                  sb.append("$DIR/java $JLINK_VM_OPTIONS -m ")
                          .append(module).append('/')
!                         .append(mainClassName)
                          .append(" $@\n");
  
                  try (BufferedWriter writer = Files.newBufferedWriter(cmd,
                          StandardCharsets.ISO_8859_1,
                          StandardOpenOption.CREATE_NEW)) {
*** 284,312 ****
                          .supportedFileAttributeViews().contains("posix")) {
                      setExecutable(cmd);
                  }
                  // generate .bat file for Windows
                  if (isWindows()) {
!                     Path bat = root.resolve(BIN_DIRNAME).resolve(module + ".bat");
                      sb = new StringBuilder();
                      sb.append("@echo off")
                              .append("\r\n");
                      sb.append("set JLINK_VM_OPTIONS=")
                              .append("\r\n");
                      sb.append("set DIR=%~dp0")
                              .append("\r\n");
                      sb.append("\"%DIR%\\java\" %JLINK_VM_OPTIONS% -m ")
                              .append(module).append('/')
!                             .append(mainClass.get())
                              .append(" %*\r\n");
  
                      try (BufferedWriter writer = Files.newBufferedWriter(bat,
                              StandardCharsets.ISO_8859_1,
                              StandardOpenOption.CREATE_NEW)) {
                          writer.write(sb.toString());
                      }
                  }
              }
          }
      }
  
      @Override
--- 306,336 ----
                          .supportedFileAttributeViews().contains("posix")) {
                      setExecutable(cmd);
                  }
                  // generate .bat file for Windows
                  if (isWindows()) {
!                     Path bat = root.resolve(BIN_DIRNAME).resolve(launcherFile + ".bat");
                      sb = new StringBuilder();
                      sb.append("@echo off")
                              .append("\r\n");
                      sb.append("set JLINK_VM_OPTIONS=")
                              .append("\r\n");
                      sb.append("set DIR=%~dp0")
                              .append("\r\n");
                      sb.append("\"%DIR%\\java\" %JLINK_VM_OPTIONS% -m ")
                              .append(module).append('/')
!                             .append(mainClassName)
                              .append(" %*\r\n");
  
                      try (BufferedWriter writer = Files.newBufferedWriter(bat,
                              StandardCharsets.ISO_8859_1,
                              StandardOpenOption.CREATE_NEW)) {
                          writer.write(sb.toString());
                      }
                  }
+             } else {
+                 throw new IllegalArgumentException(module + " doesn't contain main class & main not specified in command line");
              }
          }
      }
  
      @Override