org.springframework.core.env

## Class AbstractEnvironment

- java.lang.Object
- - org.springframework.core.env.AbstractEnvironment

All Implemented Interfaces:
  ConfigurableEnvironment, ConfigurablePropertyResolver, Environment, PropertyResolver

Direct Known Subclasses:
  MockEnvironment, StandardEnvironment

    public abstract class AbstractEnvironment
    extends Object
    implements ConfigurableEnvironment

Abstract base class for `Environment` implementations. Supports the notion of reserved default profile names and enables specifying active and default profiles through the `ACTIVE_PROFILES_PROPERTY_NAME` and `DEFAULT_PROFILES_PROPERTY_NAME` properties.

Concrete subclasses differ primarily on which `PropertySource` objects they add by default. `AbstractEnvironment` adds none. Subclasses should contribute property sources through the protected `customizePropertySources(MutablePropertySources)` hook, while clients should customize using `ConfigurableEnvironment.getPropertySources()` and working against the `MutablePropertySources` API. See `ConfigurableEnvironment` Javadoc for usage examples.

Since:
  3.1
Author:
  Chris Beams
See Also:
  `ConfigurableEnvironment`, `StandardEnvironment`

### Field Summary

Fields
`static String` `ACTIVE_PROFILES_PROPERTY_NAME` Name of property to set to specify active profiles: "spring.profiles.active".
`static String` `DEFAULT_PROFILES_PROPERTY_NAME` Name of property to set to specify profiles active by default: "spring.profiles.default".
`protected Log` `logger`
`protected static String` `RESERVED_DEFAULT_PROFILE_NAME` Name of reserved default profile name: "default".

### Constructor Summary

Constructors
Constructor and Description
`AbstractEnvironment()` Create a new `Environment` instance, calling back to `customizePropertySources(MutablePropertySources)` during construction to allow subclasses to contribute or manipulate `PropertySource` instances as appropriate.

### Method Summary

Methods
`boolean` `acceptsProfiles(String... profiles)` 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.
`void` `addActiveProfile(String profile)` Add a profile to the current set of active profiles.
`boolean` `containsProperty(String key)` Return whether the given property key is available for resolution, i.e., the value for the given key is not `null`.
`protected void` `customizePropertySources(MutablePropertySources propertySources)` Customize the set of `PropertySource` objects to be searched by this `Environment` during calls to `getProperty(String)` and related methods.
`protected Set<String>` `doGetActiveProfiles()` Return the set of active profiles as explicitly set through `setActiveProfiles(java.lang.String...)` or if the current set of active profiles is empty, check for the presence of the "spring.profiles.active" property and assign its value to the set of active profiles.
`protected Set<String>` `doGetDefaultProfiles()` Return the set of default profiles explicitly set via `setDefaultProfiles(String...)` or if the current set of default profiles consists only of reserved default profiles, then check for the presence of the "spring.profiles.default" property and assign its value (if any) to the set of default profiles.
`String[]` `getActiveProfiles()` Return the set of profiles explicitly made active for this environment.
`ConfigurableConversionService` `getConversionService()`
`String[]` `getDefaultProfiles()` Return the set of profiles to be active by default when no active profiles have been set explicitly.
`String` `getProperty(String key)` Return the property value associated with the given key, or `null` if the key cannot be resolved.
`<T> T` `getProperty(String key, Class<T> targetType)` Return the property value associated with the given key, or `null` if the key cannot be resolved.
`<T> T` `getProperty(String key, Class<T> targetType, T defaultValue)` Return the property value associated with the given key, or `defaultValue` if the key cannot be resolved.
`String` `getProperty(String key, String defaultValue)` Return the property value associated with the given key, or `defaultValue` if the key cannot be resolved.
`<T> Class<T>` `getPropertyAsClass(String key, Class<T> targetType)` Convert the property value associated with the given key to a `Class` of type `T` or `null` if the key cannot be resolved.
`MutablePropertySources` `getPropertySources()` Return the `PropertySources` for this `Environment` in mutable form, allowing for manipulation of the set of `PropertySource` objects that should be searched when resolving properties against this `Environment` object.
`String` `getRequiredProperty(String key)` Return the property value associated with the given key, converted to the given targetType (never `null`).
`<T> T` `getRequiredProperty(String key, Class<T> targetType)` Return the property value associated with the given key, converted to the given targetType (never `null`).
`protected Set<String>` `getReservedDefaultProfiles()` Return the set of reserved default profile names.
`Map<String,Object>` `getSystemEnvironment()` Return the value of `System.getenv()` if allowed by the current `SecurityManager`, otherwise return a map implementation that will attempt to access individual keys using calls to `System.getenv(String)`.
`Map<String,Object>` `getSystemProperties()` Return the value of `System.getProperties()` if allowed by the current `SecurityManager`, otherwise return a map implementation that will attempt to access individual keys using calls to `System.getProperty(String)`.
`protected boolean` `isProfileActive(String profile)` Return whether the given profile is active, or if active profiles are empty whether the profile should be active by default.
`void` `merge(ConfigurableEnvironment parent)` Append the given parent environment's active profiles, default profiles and property sources to this (child) environment's respective collections of each.
`String` `resolvePlaceholders(String text)` Resolve ${...} placeholders in the given text, replacing them with corresponding property values as resolved by `PropertyResolver.getProperty(java.lang.String)`.
`String` `resolveRequiredPlaceholders(String text)` Resolve ${...} placeholders in the given text, replacing them with corresponding property values as resolved by `PropertyResolver.getProperty(java.lang.String)`.
`void` `setActiveProfiles(String... profiles)` Specify the set of profiles active for this `Environment`.
`void` `setConversionService(ConfigurableConversionService conversionService)` Set the `ConfigurableConversionService` to be used when performing type conversions on properties.
`void` `setDefaultProfiles(String... profiles)` Specify the set of profiles to be made active by default if no other profiles are explicitly made active through `ConfigurableEnvironment.setActiveProfiles(java.lang.String...)`.
`void` `setIgnoreUnresolvableNestedPlaceholders(boolean ignoreUnresolvableNestedPlaceholders)` Set whether to throw an exception when encountering an unresolvable placeholder nested within the value of a given property.
`void` `setPlaceholderPrefix(String placeholderPrefix)` Set the prefix that placeholders replaced by this resolver must begin with.
`void` `setPlaceholderSuffix(String placeholderSuffix)` Set the suffix that placeholders replaced by this resolver must end with.
`void` `setRequiredProperties(String... requiredProperties)` Specify which properties must be present, to be verified by `ConfigurablePropertyResolver.validateRequiredProperties()`.
`void` `setValueSeparator(String valueSeparator)` Specify the separating character between the placeholders replaced by this resolver and their associated default value, or `null` if no such special character should be processed as a value separator.
`String` `toString()`
`protected void` `validateProfile(String profile)` Validate the given profile, called internally prior to adding to the set of active or default profiles.
`void` `validateRequiredProperties()` Validate that each of the properties specified by `ConfigurablePropertyResolver.setRequiredProperties(java.lang.String...)` is present and resolves to a non-`null` value.

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

### Field Detail

#### ACTIVE_PROFILES_PROPERTY_NAME

    public static final String ACTIVE_PROFILES_PROPERTY_NAME

Name of property to set to specify active profiles: "spring.profiles.active". Value may be comma delimited.

Note that certain shell environments such as Bash disallow the use of the period character in variable names. Assuming that Spring's `SystemEnvironmentPropertySource` is in use, this property may be specified as an environment variable as `SPRING_PROFILES_ACTIVE`.

See Also:
  `ConfigurableEnvironment.setActiveProfiles(java.lang.String...)`, Constant Field Values

#### DEFAULT_PROFILES_PROPERTY_NAME

    public static final String DEFAULT_PROFILES_PROPERTY_NAME

Name of property to set to specify profiles active by default: "spring.profiles.default". Value may be comma delimited.

Note that certain shell environments such as Bash disallow the use of the period character in variable names. Assuming that Spring's `SystemEnvironmentPropertySource` is in use, this property may be specified as an environment variable as `SPRING_PROFILES_DEFAULT`.

See Also:
  `ConfigurableEnvironment.setDefaultProfiles(java.lang.String...)`, Constant Field Values

#### RESERVED_DEFAULT_PROFILE_NAME

    protected static final String RESERVED_DEFAULT_PROFILE_NAME

Name of reserved default profile name: "default". If no default profile names are explicitly and no active profile names are explicitly set, this profile will automatically be activated by default.

See Also:
  `getReservedDefaultProfiles()`, `ConfigurableEnvironment.setDefaultProfiles(java.lang.String...)`, `ConfigurableEnvironment.setActiveProfiles(java.lang.String...)`, `DEFAULT_PROFILES_PROPERTY_NAME`, `ACTIVE_PROFILES_PROPERTY_NAME`, Constant Field Values

#### logger

    protected final Log logger

### Constructor Detail

#### AbstractEnvironment

    public AbstractEnvironment()

Create a new `Environment` instance, calling back to `customizePropertySources(MutablePropertySources)` during construction to allow subclasses to contribute or manipulate `PropertySource` instances as appropriate.

See Also:
  `customizePropertySources(MutablePropertySources)`

### Method Detail

#### customizePropertySources

    protected void customizePropertySources(MutablePropertySources propertySources)

Customize the set of `PropertySource` objects to be searched by this `Environment` during calls to `getProperty(String)` and related methods.

Subclasses that override this method are encouraged to add property sources using `MutablePropertySources.addLast(PropertySource)` such that further subclasses may call `super.customizePropertySources()` with predictable results. For example:

     public class Level1Environment extends AbstractEnvironment {
         @Override
         protected void customizePropertySources(MutablePropertySources propertySources) {
             super.customizePropertySources(propertySources); // no-op from base class
             propertySources.addLast(new PropertySourceA(...));
             propertySources.addLast(new PropertySourceB(...));
         }
     }

     public class Level2Environment extends Level1Environment {
         @Override
         protected void customizePropertySources(MutablePropertySources propertySources) {
             super.customizePropertySources(propertySources); // add all from superclass
             propertySources.addLast(new PropertySourceC(...));
             propertySources.addLast(new PropertySourceD(...));
         }
     }

In this arrangement, properties will be resolved against sources A, B, C, D in that order. That is to say that property source "A" has precedence over property source "D". If the `Level2Environment` subclass wished to give property sources C and D higher precedence than A and B, it could simply call `super.customizePropertySources` after, rather than before adding its own:

     public class Level2Environment extends Level1Environment {
         @Override
         protected void customizePropertySources(MutablePropertySources propertySources) {
             propertySources.addLast(new PropertySourceC(...));
             propertySources.addLast(new PropertySourceD(...));
             super.customizePropertySources(propertySources); // add all from superclass
         }
     }

The search order is now C, D, A, B as desired.

Beyond these recommendations, subclasses may use any of the `add&#42;`, `remove`, or `replace` methods exposed by `MutablePropertySources` in order to create the exact arrangement of property sources desired.

The base implementation in `customizePropertySources(org.springframework.core.env.MutablePropertySources)` registers no property sources.

Note that clients of any `ConfigurableEnvironment` may further customize property sources via the `getPropertySources()` accessor, typically within an `ApplicationContextInitializer`. For example:

     ConfigurableEnvironment env = new StandardEnvironment();
     env.getPropertySources().addLast(new PropertySourceX(...));

## A warning about instance variable access

Instance variables declared in subclasses and having default initial values should not be accessed from within this method. Due to Java object creation lifecycle constraints, any initial value will not yet be assigned when this callback is invoked by the `AbstractEnvironment()` constructor, which may lead to a `NullPointerException` or other problems. If you need to access default values of instance variables, leave this method as a no-op and perform property source manipulation and instance variable access directly within the subclass constructor. Note that assigning values to instance variables is not problematic; it is only attempting to read default values that must be avoided.

See Also:
  `MutablePropertySources`, `PropertySourcesPropertyResolver`, `ApplicationContextInitializer`

#### getReservedDefaultProfiles

    protected Set<String> getReservedDefaultProfiles()

Return the set of reserved default profile names. This implementation returns "default". Subclasses may override in order to customize the set of reserved names.

See Also:
  `RESERVED_DEFAULT_PROFILE_NAME`, `doGetDefaultProfiles()`

#### getActiveProfiles

    public String[] getActiveProfiles()

Description copied from interface: `Environment`
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 "spring.profiles.active" as a system property or by calling `ConfigurableEnvironment.setActiveProfiles(String...)`.

If no profiles have explicitly been specified as active, then any default profiles will automatically be activated.

Specified by:
  `getActiveProfiles` in interface `Environment`
See Also:
  `Environment.getDefaultProfiles()`, `ConfigurableEnvironment.setActiveProfiles(java.lang.String...)`, `ACTIVE_PROFILES_PROPERTY_NAME`

#### doGetActiveProfiles

    protected Set<String> doGetActiveProfiles()

Return the set of active profiles as explicitly set through `setActiveProfiles(java.lang.String...)` or if the current set of active profiles is empty, check for the presence of the "spring.profiles.active" property and assign its value to the set of active profiles.

See Also:
  `getActiveProfiles()`, `ACTIVE_PROFILES_PROPERTY_NAME`

#### setActiveProfiles

    public void setActiveProfiles(String... profiles)

Description copied from interface: `ConfigurableEnvironment`
Specify the set of profiles active for this `Environment`. Profiles are evaluated during container bootstrap to determine whether bean definitions should be registered with the container.

Any existing active profiles will be replaced with the given arguments; call with zero arguments to clear the current set of active profiles. Use `ConfigurableEnvironment.addActiveProfile(java.lang.String)` to add a profile while preserving the existing set.

Specified by:
  `setActiveProfiles` in interface `ConfigurableEnvironment`
See Also:
  `ConfigurableEnvironment.addActiveProfile(java.lang.String)`, `ConfigurableEnvironment.setDefaultProfiles(java.lang.String...)`, `Profile`, `ACTIVE_PROFILES_PROPERTY_NAME`

#### addActiveProfile

    public void addActiveProfile(String profile)

Description copied from interface: `ConfigurableEnvironment`
Add a profile to the current set of active profiles.

Specified by:
  `addActiveProfile` in interface `ConfigurableEnvironment`
See Also:
  `ConfigurableEnvironment.setActiveProfiles(java.lang.String...)`

#### getDefaultProfiles

    public String[] getDefaultProfiles()

Description copied from interface: `Environment`
Return the set of profiles to be active by default when no active profiles have been set explicitly.

Specified by:
  `getDefaultProfiles` in interface `Environment`
See Also:
  `Environment.getActiveProfiles()`, `ConfigurableEnvironment.setDefaultProfiles(java.lang.String...)`, `DEFAULT_PROFILES_PROPERTY_NAME`

#### doGetDefaultProfiles

    protected Set<String> doGetDefaultProfiles()

Return the set of default profiles explicitly set via `setDefaultProfiles(String...)` or if the current set of default profiles consists only of reserved default profiles, then check for the presence of the "spring.profiles.default" property and assign its value (if any) to the set of default profiles.

See Also:
  `AbstractEnvironment()`, `getDefaultProfiles()`, `DEFAULT_PROFILES_PROPERTY_NAME`, `getReservedDefaultProfiles()`

#### setDefaultProfiles

    public void setDefaultProfiles(String... profiles)

Specify the set of profiles to be made active by default if no other profiles are explicitly made active through `ConfigurableEnvironment.setActiveProfiles(java.lang.String...)`.

Calling this method removes overrides any reserved default profiles that may have been added during construction of the environment.

Specified by:
  `setDefaultProfiles` in interface `ConfigurableEnvironment`
See Also:
  `AbstractEnvironment()`, `getReservedDefaultProfiles()`

#### acceptsProfiles

    public boolean acceptsProfiles(String... profiles)

Description copied from interface: `Environment`
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 not active. For example,

    env.acceptsProfiles("p1", "!p2")

will return true if profile 'p1' is active or 'p2' is not active.

Specified by:
  `acceptsProfiles` in interface `Environment`
See Also:
  `Environment.getActiveProfiles()`, `Environment.getDefaultProfiles()`

#### isProfileActive

    protected boolean isProfileActive(String profile)

Return whether the given profile is active, or if active profiles are empty whether the profile should be active by default.

Throws:
  `IllegalArgumentException` - per `validateProfile(String)`

#### validateProfile

    protected void validateProfile(String profile)

Validate the given profile, called internally prior to adding to the set of active or default profiles.

Subclasses may override to impose further restrictions on profile syntax.

Throws:
  `IllegalArgumentException` - if the profile is null, empty, whitespace-only or begins with the profile NOT operator (!).
See Also:
  `acceptsProfiles(java.lang.String...)`, `addActiveProfile(java.lang.String)`, `setDefaultProfiles(java.lang.String...)`

#### getPropertySources

    public MutablePropertySources getPropertySources()

Description copied from interface: `ConfigurableEnvironment`
Return the `PropertySources` for this `Environment` in mutable form, allowing for manipulation of the set of `PropertySource` objects that should be searched when resolving properties against this `Environment` object. The various `MutablePropertySources` methods such as `addFirst`, `addLast`, `addBefore` and `addAfter` allow for fine-grained control over property source ordering. This is useful, for example, in ensuring that certain user-defined property sources have search precedence over default property sources such as the set of system properties or the set of system environment variables.

Specified by:
  `getPropertySources` in interface `ConfigurableEnvironment`
See Also:
  `customizePropertySources(org.springframework.core.env.MutablePropertySources)`

#### getSystemEnvironment

    public Map<String,Object> getSystemEnvironment()

Description copied from interface: `ConfigurableEnvironment`
Return the value of `System.getenv()` if allowed by the current `SecurityManager`, otherwise return a map implementation that will attempt to access individual keys using calls to `System.getenv(String)`.

Note that most `Environment` implementations will include this system environment map as a default `PropertySource` to be searched. Therefore, it is recommended that this method not be used directly unless bypassing other property sources is expressly intended.

Calls to `Map.get(Object)` on the Map returned will never throw `IllegalAccessException`; in cases where the SecurityManager forbids access to a property, `null` will be returned and an INFO-level log message will be issued noting the exception.

Specified by:
  `getSystemEnvironment` in interface `ConfigurableEnvironment`

#### getSystemProperties

    public Map<String,Object> getSystemProperties()

Description copied from interface: `ConfigurableEnvironment`
Return the value of `System.getProperties()` if allowed by the current `SecurityManager`, otherwise return a map implementation that will attempt to access individual keys using calls to `System.getProperty(String)`.

Note that most `Environment` implementations will include this system properties map as a default `PropertySource` to be searched. Therefore, it is recommended that this method not be used directly unless bypassing other property sources is expressly intended.

Calls to `Map.get(Object)` on the Map returned will never throw `IllegalAccessException`; in cases where the SecurityManager forbids access to a property, `null` will be returned and an INFO-level log message will be issued noting the exception.

Specified by:
  `getSystemProperties` in interface `ConfigurableEnvironment`

#### merge

    public void merge(ConfigurableEnvironment parent)

Description copied from interface: `ConfigurableEnvironment`
Append the given parent environment's active profiles, default profiles and property sources to this (child) environment's respective collections of each.

For any identically-named `PropertySource` instance existing in both parent and child, the child instance is to be preserved and the parent instance discarded. This has the effect of allowing overriding of property sources by the child as well as avoiding redundant searches through common property source types, e.g. system environment and system properties.

Active and default profile names are also filtered for duplicates, to avoid confusion and redundant storage.

The parent environment remains unmodified in any case. Note that any changes to the parent environment occurring after the call to `merge` will not be reflected in the child. Therefore, care should be taken to configure parent property sources and profile information prior to calling `merge`.

Specified by:
  `merge` in interface `ConfigurableEnvironment`
Parameters:
  `parent` - the environment to merge with
See Also:
  `AbstractApplicationContext.setParent(org.springframework.context.ApplicationContext)`

#### containsProperty

    public boolean containsProperty(String key)

Description copied from interface: `PropertyResolver`
Return whether the given property key is available for resolution, i.e., the value for the given key is not `null`.

Specified by:
  `containsProperty` in interface `PropertyResolver`

#### getProperty

    public String getProperty(String key)

Description copied from interface: `PropertyResolver`
Return the property value associated with the given key, or `null` if the key cannot be resolved.

Specified by:
  `getProperty` in interface `PropertyResolver`
Parameters:
  `key` - the property name to resolve
See Also:
  `PropertyResolver.getProperty(String, String)`, `PropertyResolver.getProperty(String, Class)`, `PropertyResolver.getRequiredProperty(String)`

#### getProperty

    public String getProperty(String key,
                     String defaultValue)

Description copied from interface: `PropertyResolver`
Return the property value associated with the given key, or `defaultValue` if the key cannot be resolved.

Specified by:
  `getProperty` in interface `PropertyResolver`
Parameters:
  `key` - the property name to resolve
  `defaultValue` - the default value to return if no value is found
See Also:
  `PropertyResolver.getRequiredProperty(String)`, `PropertyResolver.getProperty(String, Class)`

#### getProperty

    public <T> T getProperty(String key,
                    Class<T> targetType)

Description copied from interface: `PropertyResolver`
Return the property value associated with the given key, or `null` if the key cannot be resolved.

Specified by:
  `getProperty` in interface `PropertyResolver`
Parameters:
  `key` - the property name to resolve
  `targetType` - the expected type of the property value
See Also:
  `PropertyResolver.getRequiredProperty(String, Class)`

#### getProperty

    public <T> T getProperty(String key,
                    Class<T> targetType,
                    T defaultValue)

Description copied from interface: `PropertyResolver`
Return the property value associated with the given key, or `defaultValue` if the key cannot be resolved.

Specified by:
  `getProperty` in interface `PropertyResolver`
Parameters:
  `key` - the property name to resolve
  `targetType` - the expected type of the property value
  `defaultValue` - the default value to return if no value is found
See Also:
  `PropertyResolver.getRequiredProperty(String, Class)`

#### getPropertyAsClass

    public <T> Class<T> getPropertyAsClass(String key,
                                  Class<T> targetType)

Description copied from interface: `PropertyResolver`
Convert the property value associated with the given key to a `Class` of type `T` or `null` if the key cannot be resolved.

Specified by:
  `getPropertyAsClass` in interface `PropertyResolver`
See Also:
  `PropertyResolver.getProperty(String, Class)`

#### getRequiredProperty

    public String getRequiredProperty(String key)
                               throws IllegalStateException

Description copied from interface: `PropertyResolver`
Return the property value associated with the given key, converted to the given targetType (never `null`).

Specified by:
  `getRequiredProperty` in interface `PropertyResolver`
Throws:
  `IllegalStateException` - if the key cannot be resolved
See Also:
  `PropertyResolver.getRequiredProperty(String, Class)`

#### getRequiredProperty

    public <T> T getRequiredProperty(String key,
                            Class<T> targetType)
                          throws IllegalStateException

Description copied from interface: `PropertyResolver`
Return the property value associated with the given key, converted to the given targetType (never `null`).

Specified by:
  `getRequiredProperty` in interface `PropertyResolver`
Throws:
  `IllegalStateException` - if the given key cannot be resolved

#### setRequiredProperties

    public void setRequiredProperties(String... requiredProperties)

Description copied from interface: `ConfigurablePropertyResolver`
Specify which properties must be present, to be verified by `ConfigurablePropertyResolver.validateRequiredProperties()`.

Specified by:
  `setRequiredProperties` in interface `ConfigurablePropertyResolver`

#### validateRequiredProperties

    public void validateRequiredProperties()
                                    throws MissingRequiredPropertiesException

Description copied from interface: `ConfigurablePropertyResolver`
Validate that each of the properties specified by `ConfigurablePropertyResolver.setRequiredProperties(java.lang.String...)` is present and resolves to a non-`null` value.

Specified by:
  `validateRequiredProperties` in interface `ConfigurablePropertyResolver`
Throws:
  `MissingRequiredPropertiesException` - if any of the required properties are not resolvable.

#### resolvePlaceholders

    public String resolvePlaceholders(String text)

Description copied from interface: `PropertyResolver`
Resolve ${...} placeholders in the given text, replacing them with corresponding property values as resolved by `PropertyResolver.getProperty(java.lang.String)`. Unresolvable placeholders with no default value are ignored and passed through unchanged.

Specified by:
  `resolvePlaceholders` in interface `PropertyResolver`
Parameters:
  `text` - the String to resolve
Returns:
  the resolved String (never `null`)
See Also:
  `PropertyResolver.resolveRequiredPlaceholders(java.lang.String)`, `SystemPropertyUtils.resolvePlaceholders(String)`

#### resolveRequiredPlaceholders

    public String resolveRequiredPlaceholders(String text)
                                       throws IllegalArgumentException

Description copied from interface: `PropertyResolver`
Resolve ${...} placeholders in the given text, replacing them with corresponding property values as resolved by `PropertyResolver.getProperty(java.lang.String)`. Unresolvable placeholders with no default value will cause an IllegalArgumentException to be thrown.

Specified by:
  `resolveRequiredPlaceholders` in interface `PropertyResolver`
Returns:
  the resolved String (never `null`)
Throws:
  `IllegalArgumentException` - if given text is `null`
See Also:
  `SystemPropertyUtils.resolvePlaceholders(String, boolean)`

#### setIgnoreUnresolvableNestedPlaceholders

    public void setIgnoreUnresolvableNestedPlaceholders(boolean ignoreUnresolvableNestedPlaceholders)

Description copied from interface: `ConfigurablePropertyResolver`
Set whether to throw an exception when encountering an unresolvable placeholder nested within the value of a given property. A `false` value indicates strict resolution, i.e. that an exception will be thrown. A `true` value indicates that unresolvable nested placeholders should be passed through in their unresolved ${...} form.

Implementations of `PropertyResolver.getProperty(String)` and its variants must inspect the value set here to determine correct behavior when property values contain unresolvable placeholders.

Specified by:
  `setIgnoreUnresolvableNestedPlaceholders` in interface `ConfigurablePropertyResolver`

#### setConversionService

    public void setConversionService(ConfigurableConversionService conversionService)

Description copied from interface: `ConfigurablePropertyResolver`
Set the `ConfigurableConversionService` to be used when performing type conversions on properties.

Note: as an alternative to fully replacing the `ConversionService`, consider adding or removing individual `Converter` instances by drilling into `ConfigurablePropertyResolver.getConversionService()` and calling methods such as `#addConverter`.

Specified by:
  `setConversionService` in interface `ConfigurablePropertyResolver`
See Also:
  `PropertyResolver.getProperty(String, Class)`, `ConfigurablePropertyResolver.getConversionService()`, `ConverterRegistry.addConverter(org.springframework.core.convert.converter.Converter<?, ?>)`

#### getConversionService

    public ConfigurableConversionService getConversionService()

Specified by:
  `getConversionService` in interface `ConfigurablePropertyResolver`
Returns:
  the `ConfigurableConversionService` used when performing type conversions on properties.

  The configurable nature of the returned conversion service allows for the convenient addition and removal of individual `Converter` instances:

       ConfigurableConversionService cs = env.getConversionService();
       cs.addConverter(new FooConverter());

See Also:
  `PropertyResolver.getProperty(String, Class)`, `ConverterRegistry.addConverter(org.springframework.core.convert.converter.Converter<?, ?>)`

#### setPlaceholderPrefix

    public void setPlaceholderPrefix(String placeholderPrefix)

Description copied from interface: `ConfigurablePropertyResolver`
Set the prefix that placeholders replaced by this resolver must begin with.

Specified by:
  `setPlaceholderPrefix` in interface `ConfigurablePropertyResolver`

#### setPlaceholderSuffix

    public void setPlaceholderSuffix(String placeholderSuffix)

Description copied from interface: `ConfigurablePropertyResolver`
Set the suffix that placeholders replaced by this resolver must end with.

Specified by:
  `setPlaceholderSuffix` in interface `ConfigurablePropertyResolver`

#### setValueSeparator

    public void setValueSeparator(String valueSeparator)

Description copied from interface: `ConfigurablePropertyResolver`
Specify the separating character between the placeholders replaced by this resolver and their associated default value, or `null` if no such special character should be processed as a value separator.

Specified by:
  `setValueSeparator` in interface `ConfigurablePropertyResolver`

#### toString

    public String toString()

Overrides:
  `toString` in class `Object`