我有一堆Spring bean，它们是通过注释从类路径中获取的，例如。
@Repository("personDao")
public class PersonDaoImpl extends AbstractDaoImpl implements PersonDao {
// Implementation omitted
}
在Spring XML文件中，定义了一个PropertyPlaceholderConfigurer:
<bean id="propertyConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location" value="/WEB-INF/app.properties" />
</bean>
我想将app. properties中的一个属性注入到上面所示的bean中。我不能简单地做一些
<bean class="com.example.PersonDaoImpl">
<property name="maxResults" value="${results.max}"/>
</bean>
因为PersonDaoImpl没有出现在Spring XML文件中(它是通过注释从类路径中获取的)。我已经了解到以下内容:
@Repository("personDao")
public class PersonDaoImpl extends AbstractDaoImpl implements PersonDao {
@Resource(name = "propertyConfigurer")
protected void setProperties(PropertyPlaceholderConfigurer ppc) {
// Now how do I access results.max?
}
}
但我不清楚我如何从ppc访问我感兴趣的财产?
在我们得到Spring 3之前——它允许您使用注释直接将属性常量注入到bean中——我写了PropertyPlaceholderConfigurer bean的一个子类，它做同样的事情。所以，你可以标记你的属性设置，Spring会自动将你的属性连接到你的bean中，就像这样:
@Property(key="property.key", defaultValue="default")
public void setProperty(String property) {
this.property = property;
}
注释如下:
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.FIELD})
public @interface Property {
String key();
String defaultValue() default "";
}
PropertyAnnotationAndPlaceholderConfigurer如下所示:
public class PropertyAnnotationAndPlaceholderConfigurer extends PropertyPlaceholderConfigurer {
private static Logger log = Logger.getLogger(PropertyAnnotationAndPlaceholderConfigurer.class);
@Override
protected void processProperties(ConfigurableListableBeanFactory beanFactory, Properties properties) throws BeansException {
super.processProperties(beanFactory, properties);
for (String name : beanFactory.getBeanDefinitionNames()) {
MutablePropertyValues mpv = beanFactory.getBeanDefinition(name).getPropertyValues();
Class clazz = beanFactory.getType(name);
if(log.isDebugEnabled()) log.debug("Configuring properties for bean="+name+"["+clazz+"]");
if(clazz != null) {
for (PropertyDescriptor property : BeanUtils.getPropertyDescriptors(clazz)) {
Method setter = property.getWriteMethod();
Method getter = property.getReadMethod();
Property annotation = null;
if(setter != null && setter.isAnnotationPresent(Property.class)) {
annotation = setter.getAnnotation(Property.class);
} else if(setter != null && getter != null && getter.isAnnotationPresent(Property.class)) {
annotation = getter.getAnnotation(Property.class);
}
if(annotation != null) {
String value = resolvePlaceholder(annotation.key(), properties, SYSTEM_PROPERTIES_MODE_FALLBACK);
if(StringUtils.isEmpty(value)) {
value = annotation.defaultValue();
}
if(StringUtils.isEmpty(value)) {
throw new BeanConfigurationException("No such property=["+annotation.key()+"] found in properties.");
}
if(log.isDebugEnabled()) log.debug("setting property=["+clazz.getName()+"."+property.getName()+"] value=["+annotation.key()+"="+value+"]");
mpv.addPropertyValue(property.getName(), value);
}
}
for(Field field : clazz.getDeclaredFields()) {
if(log.isDebugEnabled()) log.debug("examining field=["+clazz.getName()+"."+field.getName()+"]");
if(field.isAnnotationPresent(Property.class)) {
Property annotation = field.getAnnotation(Property.class);
PropertyDescriptor property = BeanUtils.getPropertyDescriptor(clazz, field.getName());
if(property.getWriteMethod() == null) {
throw new BeanConfigurationException("setter for property=["+clazz.getName()+"."+field.getName()+"] not available.");
}
Object value = resolvePlaceholder(annotation.key(), properties, SYSTEM_PROPERTIES_MODE_FALLBACK);
if(value == null) {
value = annotation.defaultValue();
}
if(value == null) {
throw new BeanConfigurationException("No such property=["+annotation.key()+"] found in properties.");
}
if(log.isDebugEnabled()) log.debug("setting property=["+clazz.getName()+"."+field.getName()+"] value=["+annotation.key()+"="+value+"]");
mpv.addPropertyValue(property.getName(), value);
}
}
}
}
}
}
请随意修改口味
使用Spring的“PropertyPlaceholderConfigurer”类
一个简单的示例，显示作为bean的属性动态读取的属性文件
<bean id="placeholderConfig"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>/WEB-INF/classes/config_properties/dev/database.properties</value>
</list>
</property>
</bean>
<bean id="devDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
<property name="driverClass" value="${dev.app.jdbc.driver}"/>
<property name="jdbcUrl" value="${dev.app.jdbc.url}"/>
<property name="user" value="${dev.app.jdbc.username}"/>
<property name="password" value="${dev.app.jdbc.password}"/>
<property name="acquireIncrement" value="3"/>
<property name="minPoolSize" value="5"/>
<property name="maxPoolSize" value="10"/>
<property name="maxStatementsPerConnection" value="11000"/>
<property name="numHelperThreads" value="8"/>
<property name="idleConnectionTestPeriod" value="300"/>
<property name="preferredTestQuery" value="SELECT 0"/>
</bean>
属性文件
dev.app.jdbc.driver = com.mysql.jdbc.Driver
dev.app.jdbc.url = jdbc: mysql: / / localhost: 3306 / addvertisement
dev.app.jdbc.username =根
dev.app.jdbc.password =根
