本文以在command窗口执行最简单的 gradle -v 为例子说明

从上文提到的EntryPoint.java开始，调用该类的doAction</p><p>实际调用到Main.java  的doAction

<pre name="code" class="java">    protected void doAction(String[] args, ExecutionListener listener) {
        createActionFactory().convert(Arrays.asList(args)).execute(listener);
    }

convert是一个很重要的函数，

     * <p>Converts the given command-line arguments to an {@link Action} which performs the action requested by the
     * command-line args.

    public Action<ExecutionListener> convert(List<String> args) {
        ServiceRegistry loggingServices = createLoggingServices();

        LoggingConfiguration loggingConfiguration = new LoggingConfiguration();

        return new ExceptionReportingAction(
                new WithLogging(loggingServices, args, loggingConfiguration,
                        new JavaRuntimeValidationAction(
                            new ParseAndBuildAction(loggingServices, args))),
                new BuildExceptionReporter(loggingServices.get(StyledTextOutputFactory.class), loggingConfiguration, clientMetaData()));
    }

在convert函数中， 把

ExceptionReportingAction， WithLogging， ParseAndBuildAction 和 <pre name="code" class="java">JavaRuntimeValidationAction 用构造函数参数的方式‘串联’起来，实现逐步调用的效果

代码走到

ParseAndBuildAction.createAction

    private static class BuiltInActions implements CommandLineAction {
        public void configureCommandLineParser(CommandLineParser parser) {
            parser.option(HELP, "?", "help").hasDescription("Shows this help message.");
            parser.option(VERSION, "version").hasDescription("Print version info.");
        }

        public Runnable createAction(CommandLineParser parser, ParsedCommandLine commandLine) {
            if (commandLine.hasOption(HELP)) {
                return new ShowUsageAction(parser);
            }
            if (commandLine.hasOption(VERSION)) {
                return new ShowVersionAction();
            }
            return null;
        }
    }

进入

    private static class ShowVersionAction implements Runnable {
        public void run() {
            GradleVersion currentVersion = GradleVersion.current();

            final StringBuilder sb = new StringBuilder();
            sb.append("\n------------------------------------------------------------\nGradle ");
            sb.append(currentVersion.getVersion());
            sb.append("\n------------------------------------------------------------\n\nBuild time:   ");
            sb.append(currentVersion.getBuildTime());
            sb.append("\nBuild number: ");
            sb.append(currentVersion.getBuildNumber());
            sb.append("\nRevision:     ");
            sb.append(currentVersion.getRevision());
            sb.append("\n\nGroovy:       ");
            sb.append(GroovySystem.getVersion());
            sb.append("\nAnt:          ");
            sb.append(Main.getAntVersion());
            sb.append("\nJVM:          ");
            sb.append(Jvm.current());
            sb.append("\nOS:           ");
            sb.append(OperatingSystem.current());
            sb.append("\n");

            System.out.println(sb.toString());
        }
    }

Gradle源码入门三