org.springframework.beans.factory.config

Class PlaceholderConfigurerSupport

java.lang.Object

org.springframework.core.io.support.PropertiesLoaderSupport

org.springframework.beans.factory.config.PropertyResourceConfigurer

org.springframework.beans.factory.config.PlaceholderConfigurerSupport

All Implemented Interfaces:

Aware, BeanFactoryAware, BeanNameAware, BeanFactoryPostProcessor, Ordered, PriorityOrdered

Direct Known Subclasses:

PropertyPlaceholderConfigurer, PropertySourcesPlaceholderConfigurer

public abstract class PlaceholderConfigurerSupport
extends PropertyResourceConfigurer
implements BeanNameAware, BeanFactoryAware

Abstract base class for property resource configurers that resolve placeholders in bean definition property values. Implementations pull values from a properties file or other property source into bean definitions.

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

${...}

Example XML bean definition:

<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"/>
    <property name="driverClassName" value="${driver}"/>
    <property name="url" value="jdbc:${dbname}"/>
</bean>

Example properties file:

 driver=com.mysql.jdbc.Driver
 dbname=mysql:mydb

Annotated bean definitions may take advantage of property replacement using the @Value annotation:

@Value("${person.age}")

Implementations check 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, subclasses of this type allow filling in of explicit placeholders in bean definitions.

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 property. You can also define multiple configurers, each with its own placeholder syntax. Use ignoreUnresolvablePlaceholders to intentionally suppress throwing an exception if a placeholder cannot be resolved.

Default property values can be defined globally for each configurer instance via the properties property, or on a property-by-property basis using the default value separator which is ":" by default and customizable via setValueSeparator(String).

Example XML property with default value:

<property name="url" value="jdbc:${dbname:defaultdb}"/>

Since:

3.1

Author:

Chris Beams, Juergen Hoeller

See Also:

PropertyPlaceholderConfigurer, PropertySourcesPlaceholderConfigurer

Field Summary

Fields

Modifier and Type	Field and Description
static String	DEFAULT_PLACEHOLDER_PREFIX Default placeholder prefix: "${"
static String	DEFAULT_PLACEHOLDER_SUFFIX Default placeholder suffix: "}"
static String	DEFAULT_VALUE_SEPARATOR Default value separator: ":"
protected boolean	ignoreUnresolvablePlaceholders
protected String	nullValue
protected String	placeholderPrefix Defaults to "${"
protected String	placeholderSuffix Defaults to "}"
protected String	valueSeparator Defaults to ":"

Fields inherited from class org.springframework.core.io.support.PropertiesLoaderSupport

localOverride, localProperties, logger

Fields inherited from interface org.springframework.core.Ordered

HIGHEST_PRECEDENCE, LOWEST_PRECEDENCE

Constructor Summary

Constructors

Constructor and Description
PlaceholderConfigurerSupport()

Method Summary

Modifier and Type	Method and Description
protected void	doProcessProperties(ConfigurableListableBeanFactory beanFactoryToProcess, StringValueResolver valueResolver)
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	setNullValue(String nullValue) Set a value that should be treated as null when resolved as a placeholder value: e.g.
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	setValueSeparator(String valueSeparator) Specify the separating character between the placeholder variable and the associated default value, or null if no such special character should be processed as a value separator.

Methods inherited from class org.springframework.beans.factory.config.PropertyResourceConfigurer

convertProperties, convertProperty, convertPropertyValue, getOrder, postProcessBeanFactory, processProperties, setOrder

Methods inherited from class org.springframework.core.io.support.PropertiesLoaderSupport

loadProperties, mergeProperties, setFileEncoding, setIgnoreResourceNotFound, setLocalOverride, setLocation, setLocations, setProperties, setPropertiesArray, 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

Default placeholder prefix: "${"

See Also:

Constant Field Values

DEFAULT_PLACEHOLDER_SUFFIX

public static final String DEFAULT_PLACEHOLDER_SUFFIX

Default placeholder suffix: "}"

See Also:

Constant Field Values

DEFAULT_VALUE_SEPARATOR

public static final String DEFAULT_VALUE_SEPARATOR

Default value separator: ":"

See Also:

Constant Field Values

placeholderPrefix

protected String placeholderPrefix

Defaults to "${"

placeholderSuffix

protected String placeholderSuffix

Defaults to "}"

valueSeparator

protected String valueSeparator

Defaults to ":"

ignoreUnresolvablePlaceholders

protected boolean ignoreUnresolvablePlaceholders

nullValue

protected String nullValue

Constructor Detail

PlaceholderConfigurerSupport

public PlaceholderConfigurerSupport()

Method Detail

setPlaceholderPrefix

public void setPlaceholderPrefix(String placeholderPrefix)

Set the prefix that a placeholder string starts with. The default is "${".

setPlaceholderSuffix

public void setPlaceholderSuffix(String placeholderSuffix)

Set the suffix that a placeholder string ends with. The default is "}".

setValueSeparator

public void setValueSeparator(String valueSeparator)

Specify the separating character between the placeholder variable and the associated default value, or null if no such special character should be processed as a value separator. The default is ":".

setNullValue

public void setNullValue(String nullValue)

Set a value that should be treated as null when resolved as a placeholder value: e.g. "" (empty String) or "null".

Note that this will only apply to full property values, not to parts of concatenated values.

By default, no such null value is defined. This means that there is no way to express null as a property value unless you explicitly map a corresponding value here.

setIgnoreUnresolvablePlaceholders

public void setIgnoreUnresolvablePlaceholders(boolean ignoreUnresolvablePlaceholders)

Set whether to ignore unresolvable placeholders.

Default is "false": An exception will be thrown if a placeholder fails to resolve. Switch this flag to "true" in order to preserve the placeholder String as-is in such a case, leaving it up to other placeholder configurers to resolve it.

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. Note that this name is the actual bean name used in the factory, which may differ from the originally specified name: in particular for inner bean names, the actual bean name might have been made unique through appending "#..." suffixes. Use the BeanFactoryUtils.originalBeanName(String) method to extract the original bean name (without suffix), if desired.

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 (never null). The bean can immediately call methods on the factory.

See Also:

PropertiesLoaderSupport.setLocations(org.springframework.core.io.Resource[]), ResourceEditor

doProcessProperties

protected void doProcessProperties(ConfigurableListableBeanFactory beanFactoryToProcess,
                                   StringValueResolver valueResolver)