Spring环境

spring 运行环境 包含了 计算机的环境和Spring 配置的一些环境 这些环境配置 存在在 Environment 中我们可以通过Environment配置

public interface Environment extends PropertyResolver {

    /**
     * Return the set of profiles explicitly made active for this environment. Profiles
     * are used for creating logical groupings of bean definitions to be registered
     * conditionally, for example based on deployment environment.  Profiles can be
     * activated by setting {@linkplain AbstractEnvironment#ACTIVE_PROFILES_PROPERTY_NAME
     * "spring.profiles.active"} as a system property or by calling
     * {@link ConfigurableEnvironment#setActiveProfiles(String...)}.
     * <p>If no profiles have explicitly been specified as active, then any
     * {@linkplain #getDefaultProfiles() default profiles} will automatically be activated.
     * @see #getDefaultProfiles
     * @see ConfigurableEnvironment#setActiveProfiles
     * @see AbstractEnvironment#ACTIVE_PROFILES_PROPERTY_NAME
     */
    String[] getActiveProfiles();

    /**
     * Return the set of profiles to be active by default when no active profiles have
     * been set explicitly.
     * @see #getActiveProfiles
     * @see ConfigurableEnvironment#setDefaultProfiles
     * @see AbstractEnvironment#DEFAULT_PROFILES_PROPERTY_NAME
     */
    String[] getDefaultProfiles();

    /**
     * Return whether one or more of the given profiles is active or, in the case of no
     * explicit active profiles, whether one or more of the given profiles is included in
     * the set of default profiles. If a profile begins with '!' the logic is inverted,
     * i.e. the method will return true if the given profile is <em>not</em> active.
     * For example, <pre class="code">env.acceptsProfiles("p1", "!p2")</pre> will
     * return {@code true} if profile 'p1' is active or 'p2' is not active.
     * @throws IllegalArgumentException if called with zero arguments
     * or if any profile is {@code null}, empty or whitespace-only
     * @see #getActiveProfiles
     * @see #getDefaultProfiles
     */
    boolean acceptsProfiles(String... profiles);

}

public interface PropertyResolver {

    /**
     * Return whether the given property key is available for resolution,
     * i.e. if the value for the given key is not {@code null}.
     */
    boolean containsProperty(String key);

    /**
     * Return the property value associated with the given key,
     * or {@code null} if the key cannot be resolved.
     * @param key the property name to resolve
     * @see #getProperty(String, String)
     * @see #getProperty(String, Class)
     * @see #getRequiredProperty(String)
     */
    String getProperty(String key);

    /**
     * Return the property value associated with the given key, or
     * {@code defaultValue} if the key cannot be resolved.
     * @param key the property name to resolve
     * @param defaultValue the default value to return if no value is found
     * @see #getRequiredProperty(String)
     * @see #getProperty(String, Class)
     */
    String getProperty(String key, String defaultValue);

    /**
     * Return the property value associated with the given key,
     * or {@code null} if the key cannot be resolved.
     * @param key the property name to resolve
     * @param targetType the expected type of the property value
     * @see #getRequiredProperty(String, Class)
     */
    <T> T getProperty(String key, Class<T> targetType);

    /**
     * Return the property value associated with the given key,
     * or {@code defaultValue} if the key cannot be resolved.
     * @param key the property name to resolve
     * @param targetType the expected type of the property value
     * @param defaultValue the default value to return if no value is found
     * @see #getRequiredProperty(String, Class)
     */
    <T> T getProperty(String key, Class<T> targetType, T defaultValue);

    /**
     * Convert the property value associated with the given key to a {@code Class}
     * of type {@code T} or {@code null} if the key cannot be resolved.
     * @throws org.springframework.core.convert.ConversionException if class specified
     * by property value cannot be found or loaded or if targetType is not assignable
     * from class specified by property value
     * @see #getProperty(String, Class)
     * @deprecated as of 4.3, in favor of {@link #getProperty} with manual conversion
     * to {@code Class} via the application's {@code ClassLoader}
     */
    @Deprecated
    <T> Class<T> getPropertyAsClass(String key, Class<T> targetType);

    /**
     * Return the property value associated with the given key (never {@code null}).
     * @throws IllegalStateException if the key cannot be resolved
     * @see #getRequiredProperty(String, Class)
     */
    String getRequiredProperty(String key) throws IllegalStateException;

    /**
     * Return the property value associated with the given key, converted to the given
     * targetType (never {@code null}).
     * @throws IllegalStateException if the given key cannot be resolved
     */
    <T> T getRequiredProperty(String key, Class<T> targetType) throws IllegalStateException;

    /**
     * Resolve ${...} placeholders in the given text, replacing them with corresponding
     * property values as resolved by {@link #getProperty}. Unresolvable placeholders with
     * no default value are ignored and passed through unchanged.
     * @param text the String to resolve
     * @return the resolved String (never {@code null})
     * @throws IllegalArgumentException if given text is {@code null}
     * @see #resolveRequiredPlaceholders
     * @see org.springframework.util.SystemPropertyUtils#resolvePlaceholders(String)
     */
    String resolvePlaceholders(String text);

    /**
     * Resolve ${...} placeholders in the given text, replacing them with corresponding
     * property values as resolved by {@link #getProperty}. Unresolvable placeholders with
     * no default value will cause an IllegalArgumentException to be thrown.
     * @return the resolved String (never {@code null})
     * @throws IllegalArgumentException if given text is {@code null}
     * or if any placeholders are unresolvable
     * @see org.springframework.util.SystemPropertyUtils#resolvePlaceholders(String, boolean)
     */
    String resolveRequiredPlaceholders(String text) throws IllegalArgumentException;

}

设置环境

public class PropertyPlaceholderConfigurer extends PlaceholderConfigurerSupport {

    protected String resolvePlaceholder(String placeholder, Properties props, int systemPropertiesMode) {
        String propVal = null;
        if (systemPropertiesMode == SYSTEM_PROPERTIES_MODE_OVERRIDE) {
            propVal = resolveSystemProperty(placeholder);
        }
        if (propVal == null) {
            propVal = resolvePlaceholder(placeholder, props);
        }
        if (propVal == null && systemPropertiesMode == SYSTEM_PROPERTIES_MODE_FALLBACK) {
            propVal = resolveSystemProperty(placeholder);
        }
        return propVal;
    }

}