tools/build_rules/appengine/appengine.bzl

# Copyright 2015 The Bazel Authors. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Java AppEngine support for Bazel.

For now, it only support bundling a WebApp and running locally.

To create a WebApp for Google AppEngine, add the rules:
appengine_war(
  name = "MyWebApp",
  # Jars to use for the classpath in the webapp.
  jars = ["//java/com/google/examples/mywebapp:java"],
  # data to put in the webapp, the directory structure of the data set
  # will be maintained.
  data = ["//java/com/google/examples/mywebapp:data"],
  # Data's root path, it will be considered as the root of the data files.
  # If unspecified, the path to the current package will be used. The path is
  # relative to current package or, relative to the workspace root if starting
  # with a leading slash.
  data_path = "/java/com/google/examples/mywebapp",
)


You can also make directly a single target for it with:

java_war(
  name = "MyWebApp",
  srcs = glob(["**/*.java"]),
  resources = ["..."],
  data = ["..."],
  data_path = "...",
)

Resources will be put in the classpath whereas data will be bundled at the root
of the war file. This is strictly equivalent to (it is actually a convenience
macros that translate to that):

java_library(
  name = "libMyWebApp",
  srcs = glob(["**/*.java"]),
  resources = ["..."],
)

appengine_war(
  name = "MyWebApp",
  jars = [":libMyWebApp"],
  data = ["..."],
  data_path = "...",
)

This rule will also create a .deploy target that will try to use the AppEngine
SDK to upload your application to AppEngine. It takes an optional argument: the
APP_ID. If not specified, it uses the default APP_ID provided in the application
web.xml.
"""

jar_filetype = FileType([".jar"])

def _add_file(in_file, output, path = None):
  output_path = output
  input_path = in_file.path
  if path and input_path.startswith(path):
    output_path += input_path[len(path):]
  return [
      "mkdir -p $(dirname %s)" % output_path,
      "test -L %s || ln -s $(pwd)/%s %s\n" % (output_path, input_path,
                                              output_path)
      ]

def _make_war(zipper, input_dir, output):
  return [
      "(root=$(pwd);" +
      ("cd %s &&" % input_dir) +
      ("${root}/%s Cc ${root}/%s $(find .))" % (zipper.path, output.path))
      ]

def _common_substring(str1, str2):
  i = 0
  res = ""
  for c in str1:
    if str2[i] != c:
      return res
    res += c
    i += 1
  return res

def _short_path_dirname(path):
  sp = path.short_path
  return sp[0:len(sp)-len(path.basename)-1]

def _war_impl(ctxt):
  zipper = ctxt.file._zipper

  data_path = ctxt.attr.data_path
  if not data_path:
    data_path = _short_path_dirname(ctxt.outputs.war)
  elif data_path[0] == "/":
    data_path = data_path[1:]
  else:  # relative path
    data_path = _short_path_dirname(ctxt.outputs.war) + "/" + data_path

  war = ctxt.outputs.war
  build_output = war.path + ".build_output"
  cmd = [
      "set -e;rm -rf " + build_output,
      "mkdir -p " + build_output
      ]

  inputs = ctxt.files.jars + [zipper]
  cmd += ["mkdir -p %s" % build_output + "/WEB-INF/lib"]
  for jar in ctxt.files.jars:
    # Add the jar to WEB-INF/lib.
    cmd += _add_file(jar, build_output + "/WEB-INF/lib")
    # Add its runtime classpath to WEB-INF/lib
    if hasattr(jar, "java"):
      inputs += jar.java.transitive_runtime_deps
      for run_jar in jar.java.transitive_runtime_deps:
        cmd += _add_file(run_jar, build_output + "/WEB-INF/lib")
  for jar in ctxt.files._appengine_deps:
    cmd += _add_file(jar, build_output + "/WEB-INF/lib")
    inputs += [jar]

  inputs += ctxt.files.data
  for res in ctxt.files.data:
    # Add the data file
    cmd += _add_file(res, build_output, path = data_path)

  cmd += _make_war(zipper, build_output, war)

  ctxt.action(
      inputs = inputs,
      outputs = [war],
      mnemonic="WAR",
      command="\n".join(cmd),
      use_default_shell_env=True)

  executable = ctxt.outputs.executable
  appengine_sdk = None
  for f in ctxt.files._appengine_sdk:
    if not appengine_sdk:
      appengine_sdk = f.path
    elif not f.path.startswith(appengine_sdk):
      appengine_sdk = _common_substring(appengine_sdk, f.path)

  classpath = [
      "${JAVA_RUNFILES}/%s" % jar.short_path
      for jar in ctxt.files._appengine_jars
      ]
  substitutions = {
    "%{zipper}": ctxt.file._zipper.short_path,
    "%{war}": ctxt.outputs.war.short_path,
    "%{java}": ctxt.file._java.short_path,
    "%{appengine_sdk}": appengine_sdk,
    "%{classpath}":  (":".join(classpath)),
  }
  ctxt.template_action(
      output = executable,
      template = ctxt.file._runner_template,
      substitutions = substitutions,
      executable = True)
  ctxt.template_action(
      output = ctxt.outputs.deploy,
      template = ctxt.file._deploy_template,
      substitutions = substitutions,
      executable = True)

  runfiles = ctxt.runfiles(files = [war, executable]
                           + ctxt.files._appengine_sdk
                           + ctxt.files._appengine_jars
                           + [ctxt.file._java, ctxt.file._zipper])
  return struct(runfiles = runfiles)

appengine_war = rule(
    _war_impl,
    executable = True,
    attrs = {
        "_java": attr.label(
            default=Label("//tools/jdk:java"),
            single_file=True),
        "_zipper": attr.label(
            default=Label("//third_party/ijar:zipper"),
            single_file=True),
        "_runner_template": attr.label(
            default=Label("//tools/build_rules/appengine:runner_template"),
            single_file=True),
        "_deploy_template": attr.label(
            default=Label("//tools/build_rules/appengine:deploy_template"),
            single_file=True),
        "_appengine_sdk": attr.label(
            default=Label("//external:appengine/java/sdk")),
        "_appengine_jars": attr.label(
            default=Label("//external:appengine/java/jars")),
        "_appengine_deps": attr.label_list(
            default=[
                Label("@appengine-java//:api"),
                Label("@commons-lang//jar"),
                Label("//third_party:apache_commons_collections"),
                ]
            ),
        "jars": attr.label_list(allow_files=jar_filetype, mandatory=True),
        "data": attr.label_list(allow_files=True),
        "data_path": attr.string(),
    },
    outputs = {
        "war": "%{name}.war",
        "deploy": "%{name}.deploy",
    })

def java_war(name, data=[], data_path=None, **kwargs):
  native.java_library(name = "lib%s" % name, **kwargs)
  appengine_war(name = name,
                jars = ["lib%s" % name],
                data=data,
                data_path=data_path)