Spring Environment（二）源码分析

时间 2019-11-08

原文原文链接

Spring Environment（二）源码分析

Spring 系列目录(http://www.javashuo.com/article/p-kqecupyl-bm.html)html

Spring Environment 属性配置管理系列文章：java

1、Environment 接口

public interface Environment extends PropertyResolver {
    String[] getActiveProfiles();
    String[] getDefaultProfiles();

    // @since 5.1 废弃，改用 Profiles(Profiles.of("dev"))
    @Deprecated
    boolean acceptsProfiles(String... profiles);
    boolean acceptsProfiles(Profiles profiles);
}

Environment 是对 JDK 环境、Servlet 环境的抽象，能够获取剖面相关的信息。同时实现了 PropertyResolver 接口用于解析属性占位符和类型转换，其实是委托给 PropertySourcesPropertyResolver 完成的。spring

在其子类 ConfigurableEnvironment 接口中还提供了设置剖面和相关数据的 API。api

public interface ConfigurableEnvironment extends Environment, ConfigurablePropertyResolver {
    // 1. 设置剖面
    void setActiveProfiles(String... profiles);
    void addActiveProfile(String profile);
    void setDefaultProfiles(String... profiles);

    // 2. 属性源
    MutablePropertySources getPropertySources();
    Map<String, Object> getSystemProperties();
    Map<String, Object> getSystemEnvironment();

    // 3. 合并两个环境信息
    void merge(ConfigurableEnvironment parent);
}

2、Environment 默认实现类

Environment 的主要几个实现以下所示：ide

MockEnvironment：模拟的环境，用于测试时使用；
StandardEnvironment：标准环境，普通 Java 应用时使用，会自动注册 System.getProperties() 和 System.getenv()到环境；
StandardServletEnvironment：标准 Servlet 环境，其继承了 StandardEnvironment，Web 应用时使用，除了 StandardEnvironment 外，会自动注册 ServletConfig（DispatcherServlet）、ServletContext 及 JNDI 实例到环境；

StandardEnvironment 标准的 JDK 环境实现以下，将 OS 和 JVM 相关的配置信息都交由 StandardEnvironment 管理。源码分析

2.1 StandardEnvironment

public class StandardEnvironment extends AbstractEnvironment {
    /** System environment property source name: {@value}. */
    public static final String SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME = "systemEnvironment";

    /** JVM system properties property source name: {@value}. */
    public static final String SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME = "systemProperties";

    @Override
    protected void customizePropertySources(MutablePropertySources propertySources) {
        propertySources.addLast(new MapPropertySource(SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME, getSystemProperties()));
        propertySources.addLast(new SystemEnvironmentPropertySource(SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, getSystemEnvironment()));
    }
}

2.2 StandardServletEnvironment

StandardServletEnvironment 除了注册系统变量外，还会自动注册 ServletConfig（DispatcherServlet）、ServletContext 及 JNDI 实例到环境；测试

public class StandardServletEnvironment extends StandardEnvironment implements ConfigurableWebEnvironment {
    /** Servlet context init parameters property source name: {@value}. */
    public static final String SERVLET_CONTEXT_PROPERTY_SOURCE_NAME = "servletContextInitParams";
    /** Servlet config init parameters property source name: {@value}. */
    public static final String SERVLET_CONFIG_PROPERTY_SOURCE_NAME = "servletConfigInitParams";
    /** JNDI property source name: {@value}. */
    public static final String JNDI_PROPERTY_SOURCE_NAME = "jndiProperties";

    protected void customizePropertySources(MutablePropertySources propertySources) {
        propertySources.addLast(new StubPropertySource(SERVLET_CONFIG_PROPERTY_SOURCE_NAME));
        propertySources.addLast(new StubPropertySource(SERVLET_CONTEXT_PROPERTY_SOURCE_NAME));
        if (JndiLocatorDelegate.isDefaultJndiEnvironmentAvailable()) {
            propertySources.addLast(new JndiPropertySource(JNDI_PROPERTY_SOURCE_NAME));
        }
        super.customizePropertySources(propertySources);
    }

    // 调用 initPropertySources 替换对应的占位符
    @Override
    public void initPropertySources(@Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) {
        WebApplicationContextUtils.initServletPropertySources(getPropertySources(), servletContext, servletConfig);
    }

其中 customizePropertySources 方法是在其父类 AbstractEnvironment 的构造方法中调用的，此时 ServletConfig 和 ServletContext 相关的信息还未初始化，所以须要一个占位符，在初始化 WEB 时自动替换。this

public static void initServletPropertySources(MutablePropertySources sources,
        @Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) {

    Assert.notNull(sources, "'propertySources' must not be null");
    String name = StandardServletEnvironment.SERVLET_CONTEXT_PROPERTY_SOURCE_NAME;
    if (servletContext != null && sources.contains(name) && sources.get(name) instanceof StubPropertySource) {
        sources.replace(name, new ServletContextPropertySource(name, servletContext));
    }
    name = StandardServletEnvironment.SERVLET_CONFIG_PROPERTY_SOURCE_NAME;
    if (servletConfig != null && sources.contains(name) && sources.get(name) instanceof StubPropertySource) {
        sources.replace(name, new ServletConfigPropertySource(name, servletConfig));
    }
}

3、AbstractEnvironment

Environment 的源码很是简单，就很少说了。spa

3.1 属性定义

(1) 常量code

// 为 true 时 getSystemEnvironment() 返回空集合，屏蔽 OS 相关信息
public static final String IGNORE_GETENV_PROPERTY_NAME = "spring.getenv.ignore";

// 剖面相关的配置
public static final String ACTIVE_PROFILES_PROPERTY_NAME = "spring.profiles.active";
public static final String DEFAULT_PROFILES_PROPERTY_NAME = "spring.profiles.default";
protected static final String RESERVED_DEFAULT_PROFILE_NAME = "default";

(2) 属性

// 剖面信息，查找时先从 activeProfiles 再从 defaultProfiles 中查找
private final Set<String> activeProfiles = new LinkedHashSet<>();
private final Set<String> defaultProfiles = new LinkedHashSet<>(getReservedDefaultProfiles());

// 属性源
private final MutablePropertySources propertySources = new MutablePropertySources();
// propertyResolver 用于解析属性占位符和类型转换
private final ConfigurablePropertyResolver propertyResolver =
            new PropertySourcesPropertyResolver(this.propertySources);

3.2 剖面相关的 API

public boolean acceptsProfiles(String... profiles) {
    Assert.notEmpty(profiles, "Must specify at least one profile");
    for (String profile : profiles) {
        if (StringUtils.hasLength(profile) && profile.charAt(0) == '!') {
            if (!isProfileActive(profile.substring(1))) {
                return true;
            }
        } else if (isProfileActive(profile)) {
            return true;
        }
    }
    return false;
}

protected boolean isProfileActive(String profile) {
    // 只要 profile 不为空且不以 ! 开头
    validateProfile(profile);
    Set<String> currentActiveProfiles = doGetActiveProfiles();
    return (currentActiveProfiles.contains(profile) ||
            (currentActiveProfiles.isEmpty() && doGetDefaultProfiles().contains(profile)));
}

获取剖面信息以下：

@Override
public String[] getActiveProfiles() {
    return StringUtils.toStringArray(doGetActiveProfiles());
}

// 获取 activeProfiles，defaultProfiles 相似
protected Set<String> doGetActiveProfiles() {
    synchronized (this.activeProfiles) {
        if (this.activeProfiles.isEmpty()) {
            String profiles = getProperty(ACTIVE_PROFILES_PROPERTY_NAME);
            if (StringUtils.hasText(profiles)) {
                setActiveProfiles(StringUtils.commaDelimitedListToStringArray(
                        StringUtils.trimAllWhitespace(profiles)));
            }
        }
        return this.activeProfiles;
    }
}

3.3 获取属性

private final ConfigurablePropertyResolver propertyResolver =
        new PropertySourcesPropertyResolver(this.propertySources);

@Override
public String getProperty(String key) {
    return this.propertyResolver.getProperty(key);
}

获取属性都委托给 propertyResolver 完成了，propertyResolver 持有 propertySources 数据源，能够解析占位符和进行类型转换。

PropertyResolver 的使用参考：http://www.javashuo.com/article/p-pgbhqkkt-bs.html

天天用心记录一点点。内容也许不重要，但习惯很重要！