JAVA SE系列

1. 判断一个字符串是否是一个有效的罗马数字

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// 正则
private static final Pattern ROMAN = Pattern.compile("^(?=.)M*(C[MD]|D?C{0,3})(X[CL]|L?X{0,3})(I[XV]|V?I{0,3})$");

2. 判断一个数是否是2的整数次幂

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private static boolean isPowerOfTwo(int val) {
    return (val & -val) == val;
}

分割线

Spring 生态

1. 使用代码方式，根据条件动态排除spring boot的自动装配

  • 实现 EnvironmentPostProcessor 接口

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    public class ExcludeEnvironmentPostProcessor implements EnvironmentPostProcessor {

        private static final Logger LOGGER = LoggerFactory.getLogger(ExcludeEnvironmentPostProcessor.class);

        private static final String CONDITION_KEY = "exclude.activemq";

        private static final String SPRING_EXCLUDE_KEY = "spring.autoconfigure.exclude";

        private static final String[] CUSTOM_EXCLUDES = {"org.springframework.boot.autoconfigure.jms.activemq.ActiveMQAutoConfiguration"};

        @Override
        public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
            // 拿到条件
            String condition = environment.getProperty(CONDITION_KEY);
            if (!Boolean.parseBoolean(condition)) {
                return;
            }

            // 排除掉 activemq 自动装配
            Binder binder = Binder.get(environment);
            List<String> targetExcludes = new ArrayList<>();
            // org.springframework.boot.autoconfigure.AutoConfigurationImportSelector.getExcludeAutoConfigurationsProperty
            List<String> oldExcludes = binder.bind(SPRING_EXCLUDE_KEY, String[].class).map(Arrays::asList).orElse(Collections.emptyList());
            // 原来排除的
            targetExcludes.addAll(oldExcludes);
            // 新增需要排除的
            targetExcludes.addAll(Arrays.asList(CUSTOM_EXCLUDES));

            MutablePropertySources propertySources = environment.getPropertySources();
            Properties prop = new Properties();
            prop.put(SPRING_EXCLUDE_KEY, String.join(",", targetExcludes));
            propertySources.addFirst(new PropertiesPropertySource("customExcludeProperties", prop));
        }
    }

  • 在 META-INF/spring.factories 文件中进行配置

    org.springframework.boot.env.EnvironmentPostProcessor=com.xxx.xxx.ExcludeEnvironmentPostProcessor

    image-20241218164910621