public class A{
private B b;
}
public class B{
}
applicationContext.xml
<bean id="aBean" class="A">
<property name="b"> ??? </property>
</bean>
How to create an instance of A with b = null when using context.getBean("aBean")?
I have tried <property name="b"><null/></property>, but this doesn't work.
Actually it will be null by default. No need for specific configuration, i.e. just omit <property> element.
And actually
<bean id="aBean" class="A">
<property name="b"><null /></property>
</bean>
should work: http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/beans.html#beans-null-element
Huh? Just don't do anything.
<bean id="aBean" class="A"/>
In Java object references are null by default.
Related
I am trying to use consul for centralised configuration for spring application. When I use annotation based configuration like Example 1 it works perfectly.
//Example 1
#Configuration
#EnableConsulPropertySource({"root/api/defaults", "root/global/defaults"})
public class ApplicationConfiguration {
#Value("httpclient.pool.maxtotal")
private int maxTotal;
#Value("httpclient.pool.defaultmaxperroute")
private int maxPerRoute;
...
}
However I could not find a way to use consul properties directly in xml.
<bean id="properties" class="org.springframework.SomeBeanToEnableConsulInXMLConfig">
<property name="locations">
<list>
<value>root/api/defaults</value>
<value>root/global/defaults</value>
</list>
</property>
</bean>
...
<bean name="http.client" class="com.xxx.HTTPClient">
<property name="maxTotal" value="${httpclient.pool.maxtotal}" />
<property name="defaultMaxPerRoute" value="${httpclient.pool.defaultmaxperroute}" />
</bean>
Does spring has something like SomeBeanToEnableConsulInXMLConfig or any hints on implementing this class?
I'm trying to inject a list of Class. I want a list of classes, not objects.
My class looks like this:
public class CodeServiceImpl{
private List<Class<?>> codeList;
// getter and setter
My spring configuration file (I'm not using annotations but xml) is
<bean id="myCodeServiceImpl" class = "net.croz.service.CodeServiceImpl">
<property name="codeList">
<list>
<ref bean="myAddress"/>
<ref bean="myCity"/>
<ref bean="myCountry"/>
</list>
</property>
</bean>
<bean id="myAddress" class="java.lang.Class" factory-method="forName">
<constructor-arg value="net.croz.model.Address"/>
</bean>
<bean id="myCity" class="java.lang.Class" factory-method="forName">
<constructor-arg value="net.croz.model.City"/>
</bean>
<bean id="myCountry" class="java.lang.Class" factory-method="forName">
<constructor-arg value="net.croz.model.Country"/>
</bean>
But the list codeList isn't being populated. It ends up being a null object. Thank you for your help.
Actually it works as is:
<bean class="com.my.proj.Foo">
<constructor-arg value="java.lang.String, org.springframework.util.StringUtils, byte[]"/>
</bean>
where Foo is:
public class Foo {
private final List<Class<?>> codeList;
public Foo(Class<?>... codeList) {
this.codeList = Arrays.asList(codeList);
}
}
The ConversionService does the stuff for converting comma-separated string to the Class<?>[] and tries to resolve each class on its own using BeanClassLoader
I am trying to inject the aspects in a service. For this service I am creating a proxied object using classic way.
I have written a bean- baseProxy of type (ProxyFactoryBean) which contains a list of all the required advices.
<bean id="baseProxy" class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="interceptorNames">
<list>
<value>methodInvocationAdvice</value>
</list>
</property>
</bean>
I am creating a proxy for the service like this :
<bean id="singproxy" parent="baseProxy">
<property name="target" ref="singtarget" />
<property name="targetClass" value="com.spring.learning.SingingService"></property>
</bean>
Which doesn't work but when I revert these two properties and write like this :
<bean id="singproxy" parent="baseProxy">
<property name="targetClass" value="com.spring.learning.SingingService"></property>
<property name="target" ref="singtarget" />
</bean>
To my surprise it works fine. In spring does it matter on the order for bean ? Or its a special case with ProxyFactoryBean?
I tried with Spring 3.0 I am not sure same behavior exists with previous versions.
Concerning target and targetClass, It's one or the other, but not both. Here's the relevant source (from org.springframework.aop.framework.AdvisedSupport), a parent class of ProxyFactoryBean:
public void setTarget(Object target) {
setTargetSource(new SingletonTargetSource(target));
}
public void setTargetSource(TargetSource targetSource) {
this.targetSource = (targetSource != null ? targetSource : EMPTY_TARGET_SOURCE);
}
public void setTargetClass(Class targetClass) {
this.targetSource = EmptyTargetSource.forClass(targetClass);
}
As you can see, both setTarget() and setTargetClass() write to the same field, so the last assignment wins.
I have the following configuration in my applicationContext.xml:
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>classpath:app.properties</value>
</list>
</property>
</bean>
Now, in my java class, how can I read the values from the file app.properties?
With Spring 3.0 you can use the #Value annotation.
#Component
class MyComponent {
#Value("${valueKey}")
private String valueFromPropertyFile;
}
Actually PropertyPlaceholderConfigurer is useful to inject values to spring context using properties.
Example XML context definition:
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName"><value>${driver}</value></property>
<property name="url"><value>jdbc:${dbname}</value></property>
</bean>`
Example properties file:
driver=com.mysql.jdbc.Driver
dbname=mysql:mydb
Or you can create bean like
<bean name="myBean" value="${some.property.key}" />
and then inject this bean into your class
I want to do something like the following in spring:
<beans>
...
<bean id="bean1" ... />
<bean id="bean2">
<property name="propName" value="bean1.foo" />
...
I would think that this would access the getFoo() method of bean1 and call the setPropName() method of bean2, but this doesn't seem to work.
What I understood:
You have a bean (bean1) with a
property called "foo"
You have another bean (bean2) with a
property named "propName", wich also
has to have the same "foo" that in
bean1.
why not doing this:
<beans>
...
<bean id="foo" class="foopackage.foo"/>
<bean id="bean1" class="foopackage.bean1">
<property name="foo" ref="foo"/>
</bean>
<bean id="bean2" class="foopackage.bean2">
<property name="propName" ref="foo"/>
</bean>
....
</beans>
Doing this, your bean2 is not coupled to bean1 like in your example. You can change bean1 and bean2 without affecting each other.
If you REALLY need to do the injection you proposed, you can use:
<util:property-path id="propName" path="bean1.foo"/>
You need to use PropertyPathFactoryBean:
<bean id="bean2" depends-on="bean1">
<property name="propName">
<bean class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
<property name="targetBeanName" value="bean1"/>
<property name="propertyPath" value="foo"/>
</bean>
</property>
</bean>
I think you have to inject bean1, then get foo manually because of a timing issue. When does the framework resolve the value of the target bean?
You could create a pointer bean and configure that.
class SpringRef {
private String targetProperty;
private Object targetBean;
//getters/setters
public Object getValue() {
//resolve the value of the targetProperty on targetBean.
}
}
Common-BeanUtils should be helpful.