org.springframework.beans.factory.config
Class PropertyPlaceholderConfigurer

java.lang.Object
  extended by org.springframework.core.io.support.PropertiesLoaderSupport
      extended by org.springframework.beans.factory.config.PropertyResourceConfigurer
          extended by org.springframework.beans.factory.config.PropertyPlaceholderConfigurer
All Implemented Interfaces:
BeanFactoryAware, BeanNameAware, BeanFactoryPostProcessor, Ordered
Direct Known Subclasses:
PreferencesPlaceholderConfigurer, ServletContextPropertyPlaceholderConfigurer

public class PropertyPlaceholderConfigurer
extends PropertyResourceConfigurer
implements BeanNameAware, BeanFactoryAware

A property resource configurer that resolves placeholders in bean property values of context definitions. It pulls values from a properties file into bean definitions.

The default placeholder syntax follows the Ant / Log4J / JSP EL style:

 ${...}

Example XML context definition:

 <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
   <property name="driverClassName"><value>${driver}</value></property>
   <property name="url"><value>jdbc:${dbname}</value></property>
 </bean>
Example properties file:
 driver=com.mysql.jdbc.Driver
 dbname=mysql:mydb
PropertyPlaceholderConfigurer checks simple property values, lists, maps, props, and bean names in bean references. Furthermore, placeholder values can also cross-reference other placeholders, like:
 rootPath=myrootdir
 subPath=${rootPath}/subdir
In contrast to PropertyOverrideConfigurer, this configurer allows to fill in explicit placeholders in context definitions. Therefore, the original definition cannot specify any default values for such bean properties, and the placeholder properties file is supposed to contain an entry for each defined placeholder.

If a configurer cannot resolve a placeholder, a BeanDefinitionStoreException will be thrown. If you want to check against multiple properties files, specify multiple resources via the "locations" setting. You can also define multiple PropertyPlaceholderConfigurers, each with its own placeholder syntax.

Default property values can be defined via "properties", to make overriding definitions in properties files optional. A configurer will also check against system properties (e.g. "user.dir") if it cannot resolve a placeholder with any of the specified properties. This can be customized via "systemPropertiesMode".

Note that the context definition is aware of being incomplete; this is immediately obvious when looking at the XML definition file.

Property values can be converted after reading them in, through overriding the convertPropertyValue method. For example, encrypted values can be detected and decrypted accordingly before processing them.

Since:
02.10.2003
Author:
Juergen Hoeller
See Also:
PropertiesLoaderSupport.setLocations(org.springframework.core.io.Resource[]), PropertiesLoaderSupport.setProperties(java.util.Properties), setPlaceholderPrefix(java.lang.String), setPlaceholderSuffix(java.lang.String), setSystemPropertiesModeName(java.lang.String), System.getProperty(String), PropertyResourceConfigurer.convertPropertyValue(java.lang.String), PropertyOverrideConfigurer

Field Summary
static String DEFAULT_PLACEHOLDER_PREFIX
           
static String DEFAULT_PLACEHOLDER_SUFFIX
           
static int SYSTEM_PROPERTIES_MODE_FALLBACK
          Check system properties if not resolvable in the specified properties.
static int SYSTEM_PROPERTIES_MODE_NEVER
          Never check system properties.
static int SYSTEM_PROPERTIES_MODE_OVERRIDE
          Check system properties first, before trying the specified properties.
 
Fields inherited from class org.springframework.core.io.support.PropertiesLoaderSupport
logger, XML_FILE_EXTENSION
 
Constructor Summary
PropertyPlaceholderConfigurer()
           
 
Method Summary
protected  String parseStringValue(String strVal, Properties props, String originalPlaceholder)
          Parse the given String value recursively, to be able to resolve nested placeholders (when resolved property values in turn contain placeholders again).
protected  void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, Properties props)
          Apply the given Properties to the bean factory.
protected  String resolvePlaceholder(String placeholder, Properties props)
          Resolve the given placeholder using the given properties.
protected  String resolvePlaceholder(String placeholder, Properties props, int systemPropertiesMode)
          Resolve the given placeholder using the given properties, performing a system properties check according to the given mode.
 void setBeanFactory(BeanFactory beanFactory)
          Only necessary to check that we're not parsing our own bean definition, to avoid failing on unresolvable placeholders in properties file locations.
 void setBeanName(String beanName)
          Only necessary to check that we're not parsing our own bean definition, to avoid failing on unresolvable placeholders in properties file locations.
 void setIgnoreUnresolvablePlaceholders(boolean ignoreUnresolvablePlaceholders)
          Set whether to ignore unresolvable placeholders.
 void setPlaceholderPrefix(String placeholderPrefix)
          Set the prefix that a placeholder string starts with.
 void setPlaceholderSuffix(String placeholderSuffix)
          Set the suffix that a placeholder string ends with.
 void setSystemPropertiesMode(int systemPropertiesMode)
          Set how to check system properties: as fallback, as override, or never.
 void setSystemPropertiesModeName(String constantName)
          Set the system property mode by the name of the corresponding constant, e.g.
 
Methods inherited from class org.springframework.beans.factory.config.PropertyResourceConfigurer
convertProperties, convertPropertyValue, getOrder, postProcessBeanFactory, setOrder
 
Methods inherited from class org.springframework.core.io.support.PropertiesLoaderSupport
loadProperties, mergeProperties, setFileEncoding, setIgnoreResourceNotFound, setLocalOverride, setLocation, setLocations, setProperties, setPropertiesPersister
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

DEFAULT_PLACEHOLDER_PREFIX

public static final String DEFAULT_PLACEHOLDER_PREFIX
See Also:
Constant Field Values

DEFAULT_PLACEHOLDER_SUFFIX

public static final String DEFAULT_PLACEHOLDER_SUFFIX
See Also:
Constant Field Values

SYSTEM_PROPERTIES_MODE_NEVER

public static final int SYSTEM_PROPERTIES_MODE_NEVER
Never check system properties.

See Also:
Constant Field Values

SYSTEM_PROPERTIES_MODE_FALLBACK

public static final int SYSTEM_PROPERTIES_MODE_FALLBACK
Check system properties if not resolvable in the specified properties. This is the default.

See Also:
Constant Field Values

SYSTEM_PROPERTIES_MODE_OVERRIDE

public static final int SYSTEM_PROPERTIES_MODE_OVERRIDE
Check system properties first, before trying the specified properties. This allows system properties to override any other property source.

See Also:
Constant Field Values
Constructor Detail

PropertyPlaceholderConfigurer

public PropertyPlaceholderConfigurer()
Method Detail

setPlaceholderPrefix

public void setPlaceholderPrefix(String placeholderPrefix)
Set the prefix that a placeholder string starts with. The default is "${".

See Also:
DEFAULT_PLACEHOLDER_PREFIX

setPlaceholderSuffix

public void setPlaceholderSuffix(String placeholderSuffix)
Set the suffix that a placeholder string ends with. The default is "}".

See Also:
DEFAULT_PLACEHOLDER_SUFFIX

setSystemPropertiesModeName

public void setSystemPropertiesModeName(String constantName)
                                 throws IllegalArgumentException
Set the system property mode by the name of the corresponding constant, e.g. "SYSTEM_PROPERTIES_MODE_OVERRIDE".

Parameters:
constantName - name of the constant
Throws:
IllegalArgumentException - if an invalid constant was specified
See Also:
setSystemPropertiesMode(int)

setSystemPropertiesMode

public void setSystemPropertiesMode(int systemPropertiesMode)
Set how to check system properties: as fallback, as override, or never. For example, will resolve ${user.dir} to the "user.dir" system property.

The default is "fallback": If not being able to resolve a placeholder with the specified properties, a system property will be tried. "override" will check for a system property first, before trying the specified properties. "never" will not check system properties at all.

See Also:
SYSTEM_PROPERTIES_MODE_NEVER, SYSTEM_PROPERTIES_MODE_FALLBACK, SYSTEM_PROPERTIES_MODE_OVERRIDE, setSystemPropertiesModeName(java.lang.String)

setIgnoreUnresolvablePlaceholders

public void setIgnoreUnresolvablePlaceholders(boolean ignoreUnresolvablePlaceholders)
Set whether to ignore unresolvable placeholders. Default is false: An exception will be thrown if a placeholder cannot not be resolved.


setBeanName

public void setBeanName(String beanName)
Only necessary to check that we're not parsing our own bean definition, to avoid failing on unresolvable placeholders in properties file locations. The latter case can happen with placeholders for system properties in resource locations.

Specified by:
setBeanName in interface BeanNameAware
Parameters:
beanName - the name of the bean in the factory
See Also:
PropertiesLoaderSupport.setLocations(org.springframework.core.io.Resource[]), ResourceEditor

setBeanFactory

public void setBeanFactory(BeanFactory beanFactory)
Only necessary to check that we're not parsing our own bean definition, to avoid failing on unresolvable placeholders in properties file locations. The latter case can happen with placeholders for system properties in resource locations.

Specified by:
setBeanFactory in interface BeanFactoryAware
Parameters:
beanFactory - owning BeanFactory (may not be null). The bean can immediately call methods on the factory.
See Also:
PropertiesLoaderSupport.setLocations(org.springframework.core.io.Resource[]), ResourceEditor

processProperties

protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess,
                                 Properties props)
                          throws BeansException
Description copied from class: PropertyResourceConfigurer
Apply the given Properties to the bean factory.

Specified by:
processProperties in class PropertyResourceConfigurer
Parameters:
beanFactoryToProcess - the bean factory used by the application context
props - the Properties to apply
Throws:
BeansException - in case of errors

parseStringValue

protected String parseStringValue(String strVal,
                                  Properties props,
                                  String originalPlaceholder)
                           throws BeanDefinitionStoreException
Parse the given String value recursively, to be able to resolve nested placeholders (when resolved property values in turn contain placeholders again).

Parameters:
strVal - the String value to parse
props - the Properties to resolve placeholders against
originalPlaceholder - the original placeholder, used to detect circular references between placeholders. Only non-null if we're parsing a nested placeholder.
Throws:
BeanDefinitionStoreException - if invalid values are encountered
See Also:
resolvePlaceholder(String, java.util.Properties, int)

resolvePlaceholder

protected String resolvePlaceholder(String placeholder,
                                    Properties props,
                                    int systemPropertiesMode)
Resolve the given placeholder using the given properties, performing a system properties check according to the given mode.

Default implementation delegates to resolvePlaceholder (placeholder, props) before/after the system properties check.

Subclasses can override this for custom resolution strategies, including customized points for the system properties check.

Parameters:
placeholder - the placeholder to resolve
props - the merged properties of this configurer
systemPropertiesMode - the system properties mode, according to the constants in this class
Returns:
the resolved value, of null if none
See Also:
setSystemPropertiesMode(int), System.getProperty(java.lang.String), resolvePlaceholder(String, java.util.Properties)

resolvePlaceholder

protected String resolvePlaceholder(String placeholder,
                                    Properties props)
Resolve the given placeholder using the given properties. Default implementation simply checks for a corresponding property key.

Subclasses can override this for customized placeholder-to-key mappings or custom resolution strategies, possibly just using the given properties as fallback.

Note that system properties will still be checked before respectively after this method is invoked, according to the system properties mode.

Parameters:
placeholder - the placeholder to resolve
props - the merged properties of this configurer
Returns:
the resolved value, of null if none
See Also:
setSystemPropertiesMode(int)


Copyright (c) 2002-2005 The Spring Framework Project.