Do I have to give ids to the elements of a list of Bars ?
<list value-type="foo.Bar">
<bean p:p1="someP1Value" p:p2="aP2Value" />
</list>
I get
Caused by: org.springframework.beans.factory.parsing.BeanDefinitionParsingException:
Configuration problem: Unnamed bean definition specifies neither 'class' nor 'parent'
nor 'factory-bean' - can't generate bean name
for this.
How can I omit the bean ids?
Well, the error message is pretty clear. When defining a <bean/> you must either specify class or parent attribute:
<list>
<bean class="foo.Bar" p:p1="someP1ValueA" p:p2="aP2ValueA"/>
<bean class="foo.Bar" p:p1="someP1ValueB" p:p2="aP2ValueB"/>
<bean class="foo.BarSubclass" p:p1="someP1ValueC" p:p2="aP2ValueC"/>
</list>
If you want to avoid exceesive use of class attribute, you can take advantage of parent feature:
<bean id="bar" abstract="true" class="foo.Bar"/>
<list value-type="foo.Bar">
<bean parent="bar" p:p1="someP1ValueA" p:p2="aP2ValueA"/>
<bean parent="bar" p:p1="someP1ValueB" p:p2="aP2ValueB"/>
<bean parent="bar" p:p1="someP1ValueC" p:p2="aP2ValueC" class="foo.BarSubclass"/>
</list>
What are the p:p1 and p:p2 namespaces?
Related
I have two simple beans. In the first bean it calls a init-method and return string value.
Now I want to this returned string from first bean init-method , inject to my second bean
helloWorldBean3 property newKey. Please advise me on how to implement this requirement.
<bean id="helloWorldBean2" init-method="loadKey"
class="com.java.snippets.enterprise.services.HelloWorld2">
<property name="key" value="${key.supportiveFile}" />
<bean id="helloWorldBean3"
class="com.java.snippets.enterprise.services.HelloWorld">
<property name="newKey" ref="???" />
</bean>
Try using Spring EL like so:
<bean id="helloWorldBean3"
class="com.java.snippets.enterprise.services.HelloWorld">
<property name="newKey" value=""#{helloWorldBean2.loadKey()}"" />
</bean>
I have a factory bean that produces List. But I call this factory multiple times meaning I end up with a lot of beans of type List.
I have another bean that has a property of type List. Somehow I need to put all the List beans in to one single list and provide it as a property using Spring XML.
How do I do this?
<bean id="usefulBean" class="...">
<property name="listProperty" ref="listX1AndX2AndX3AndSoOn">
</bean>
<bean id="listX1" factory-bean="anInstanceFactory" factory-method="create">
...
</bean>
<bean id="listX2" factory-bean="anInstanceFactory" factory-method="create">
...
</bean>
<bean id="listX3" factory-bean="anInstanceFactory" factory-method="create">
...
</bean>
I have the following configuration in my applicationContext.xml:
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>classpath:app.properties</value>
</list>
</property>
</bean>
Now, in my java class, how can I read the values from the file app.properties?
With Spring 3.0 you can use the #Value annotation.
#Component
class MyComponent {
#Value("${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 have a string property which looks similar to the following example:
<property name="mappingData">
<list>
<bean class="com.company.product.longNamingStandard.migration.extractor.FieldMapping">
<property name="elementName" value="entitlement.user"/>
<property name="mapping" value="DocUsers"/>
</bean>
<bean class="com.company.product.longNamingStandard.migration.extractor.FieldMapping">
<property name="elementName" value="entitlement.contributor"/>
<property name="mapping" value="DocContributors"/>
</bean>
</list>
</property>
The long class name(s) effect readability & also create a refactoring overhead.
Is it possible to alias the class name and use a short name to declare the beans? Or is there an alternate best practice I'm missing?
Probably a bit late for you, but hopefully useful for others:
You can use parent beans to accomplish this.
First declare a parent bean as a template:
<bean id="FieldMapping" class="com.company.product.longNamingStandard.migration.extractor.FieldMapping"/>
Then use it elsewhere, using the parent attribute.
<property name="mappingData">
<list>
<bean parent="FieldMapping">
<property name="elementName" value="entitlement.user"/>
<property name="mapping" value="DocUsers"/>
</bean>
<bean parent="FieldMapping">
<property name="elementName" value="entitlement.contributor"/>
<property name="mapping" value="DocContributors"/>
</bean>
</list>
</property>
Please note my convention here is to use upper case id's here for the parent template beans.
each <bean/> comes with an attribute of name and id to help you reference those beans later in your configuration.
I would suggest using the id for declaring the bean.
your config could look like:
<bean id="fooBean" class="com.example.foo"/>
<bean id="barBean" class="com.example.bar"/>
<list>
<ref>fooBean</ref>
<ref>barBean</ref>
</list>
You may try to represent your mapping in some short form, and then convert it to the list of FieldMappings. For example, mappings from your snippet may be represented as a map.
As a theoretic exercise in Spring 3 you can do this with Spring Expression Language (if FieldMapping has the apropriate constructor):
<util:map id = "m">
<entry name = "entitlement.user" value = "DocUsers" />
<entry name = "entitlement.contributor" value = "DocContributors" />
</util:map>
...
<property name = "mappingData"
value = "#{m.![new com.company.product.longNamingStandard.migration.extractor.FieldMapping(key, value)]}" />
If this expression is too obscure, you may implement a FactoryBean to take a short form of your mapping data (for example, a map, as in this example) and return a configured list of FieldMappings:
<property name = "mappingData">
<bean class = "FieldMappingListFactoryBean">
<property name = "mappings">
<map>
<entry name = "entitlement.user" value = "DocUsers" />
<entry name = "entitlement.contributor" value = "DocContributors" />
</map>
</property>
</bean>
</property>
However, if your field mappings are some kind of reusable DSL, you may try to think about implementing a namespace extension.
I found a way to simulate an effect similar to a "import com.Foo;" in java code. The best option I could find was to use a PropertyPlaceholderConfigurer with local properties defined. Using your example, here's the configuration that you would put at the top of your spring config file to define a "class_FieldMapping" property:
<bean
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<description>Define properties equivalent to "import foo;" in java source</description>
<property name="properties">
<props>
<prop key="class_FieldMapping">com.company.product.longNamingStandard.migration.extractor.FieldMapping</prop>
</props>
</property>
</bean>
Then, you can use that property within your beans:
<property name="mappingData">
<list>
<bean class="${class_FieldMapping}">
...
</bean>
<bean class="${class_FieldMapping}">
...
</bean>
</list>
</property>
This has the benefit that use can also use it for things where you actually need the class name, and can't reference an instance of an object:
<util:constant static-field="${class_FieldMapping}.MYSTATICVAR" />
Why not declare those inner beans as separate top-level beans with their own names, and then reference them in the list ?
If I use PropertyPlaceholderConfigurer it leads to several exceptions in debug log. It works, but it seems it doesn't work on the first try.
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.