SPRING BOOT启动命令参数及源码详析

java -jar xxx.jar abc def 

java -jar -Dserver.port=8081 xxx.jar

@RestController
public class ArgumentsController {
  @Resource
  private ApplicationArguments arguments;
}

@RestController
public class ParamController {
  @Value("${server.port}")
  private String serverPort;
}

String systemServerPort = System.getProperty("server.port");

java -jar --server.port=8081 xxx.jar

@RestController
public class ArgumentsController {
  @Resource
  private ApplicationArguments arguments;
  @GetMapping("/args")
  public String getArgs() {
    System.out.println("# 非选项参数数量: " + arguments.getNonOptionArgs().size());
    System.out.println("# 选项参数数量: " + arguments.getOptionNames().size());
    System.out.println("# 非选项具体参数:");
    arguments.getNonOptionArgs().forEach(System.out::println);
    System.out.println("# 选项参数具体参数:");
    arguments.getOptionNames().forEach(optionName -> {
      System.out.println("--" + optionName + "=" + arguments.getOptionValues(optionName));
    });
    return "success";
  }
}

public interface ApplicationArguments {
  /**
   * 原始参数数组（未经过处理的参数）
   */
  String[] getSourceArgs();
  /**
   * 选项参数名称
   */
  Set<String> getOptionNames();
  /**
   * 根据名称校验是否包含选项参数
   */
  boolean containsOption(String name);
  /**
   * 根据名称获得选项参数
   */
  List<String> getOptionValues(String name);
  /**
   * 获取非选项参数列表
   */
  List<String> getNonOptionArgs();
}

public ConfigurableApplicationContext run(String... args) {
  try {
    ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
    // ...
    prepareContext(context, environment, listeners, // ...
  } catch (Throwable ex) {
    // ...
  }
  return context;
}

public class DefaultApplicationArguments implements ApplicationArguments {
  private final Source source;
  private final String[] args;
  public DefaultApplicationArguments(String... args) {
    Assert.notNull(args, "Args must not be null");
    this.source = new Source(args);
    this.args = args;
  }
  // ...
  @Override
  public List<String> getOptionValues(String name) {
    List<String> values = this.source.getOptionValues(name);
    return (values != null) ? Collections.unmodifiableList(values) : null;
  }
  private static class Source extends SimpleCommandLinePropertySource {
    Source(String[] args) {
      super(args);
    }
    // ...
  }
}

public SimpleCommandLinePropertySource(String... args) {
  super(new SimpleCommandLineArgsParser().parse(args));
}

class SimpleCommandLineArgsParser {
  public CommandLineArgs parse(String... args) {
    CommandLineArgs commandLineArgs = new CommandLineArgs();
    for (String arg : args) {
      // --开头的选参数解析
      if (arg.startsWith("--")) {
        // 获得key=value或key值
        String optionText = arg.substring(2, arg.length());
        String optionName;
        String optionValue = null;
        // 如果是key=value格式则进行解析
        if (optionText.contains("=")) {
          optionName = optionText.substring(0, optionText.indexOf('='));
          optionValue = optionText.substring(optionText.indexOf('=')+1, optionText.length());
        } else {
          // 如果是仅有key（--foo）则获取其值
          optionName = optionText;
        }
        // 如果optionName为空或者optionValue不为空但optionName为空则抛出异常
        if (optionName.isEmpty() || (optionValue != null && optionValue.isEmpty())) {
          throw new IllegalArgumentException("Invalid argument syntax: " + arg);
        }
        // 封装入CommandLineArgs
        commandLineArgs.addOptionArg(optionName, optionValue);
      } else {
        commandLineArgs.addNonOptionArg(arg);
      }
    }
    return commandLineArgs;
  }
}

private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,
    SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
  // ...
  ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
  // 通过beanFactory将ApplicationArguments的对象注入Spring容器
  beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
  // ...
}