If I have:
#Autowired private ApplicationContext ctx;
I can get beans and resources by using one of the the getBean methods. However, I can't figure out how to get property values.
Obviously, I can create a new bean which has an #Value property like:
private #Value("${someProp}") String somePropValue;
What method do I call on the ApplicationContext object to get that value without autowiring a bean?
I usually use the #Value, but there is a situation where the SPeL expression needs to be dynamic, so I can't just use an annotation.
In the case where SPeL expression needs to be dynamic, get the property value manually:
somePropValue = ctx.getEnvironment().getProperty("someProp");
If you are stuck on Spring pre 3.1, you can use
somePropValue = ctx.getBeanFactory().resolveEmbeddedValue("${someProp}");
Assuming that the ${someProp} property comes from a PropertyPlaceHolderConfigurer, that makes things difficult. The PropertyPlaceholderConfigurer is a BeanFactoryPostProcessor and as such only available at container startup time. So the properties are not available to a bean at runtime.
A solution would be to create some sort of a value holder bean that you initialize with the property / properties you need.
#Component
public class PropertyHolder{
#Value("${props.foo}") private String foo;
#Value("${props.bar}") private String bar;
// + getter methods
}
Now inject this PropertyHolder wherever you need the properties and access the properties through the getter methods
Related
I am using spring framework.
I am using objectMapper to desiriale store.json file:
service:
objectMapper.readValue(new File(jsonFilePath), Store.class)
store.json:
{
"type": "Store",
"name": "myStore",
}
Store.class:
#Value("${store.size:1000}")
private Integer sroreSize;
#autowire
private storePersistency storePersistency;
public Store(#JsonProperty("name") String name) {
super(name);
}
I am trying find out how to #autowire beans and #value properties in store.class, beans and properties that exist in applicationContext.
In current example sroreSize and storePersistency still null.
I know that I can inject fields to object mapper and then use #JacksonInject annotation but I have a lot of field to inject - not a good option for me.
Custom desirializer also not a good option for me.
Is there any way not to use custom desirializer or not to inject every bean/property that I need in store.class?
Something that injects all the beans and properties and I simply can use it in Store.class.
So you want some Store fields like storePersistency and sroreSize to be initialized once at application startup (which is when Spring will setup the application context) and then at runtime create multiple different Store objects differing in some fields as name that are initialized by Jackson.
I suggest annotating Store with #Component to get Spring to initialize #Value and #Autowired fields. The #Scope annotation will cause a new independent Store instance to be created each time. Simplified example:
#Component
#Scope(SCOPE_PROTOTYPE)
class Store {
private String name;
#Value("${store.size:1000}")
private Integer sroreSize;
}
Then the key is method readerForUpdating where you can pass an existing instance of Store and Jackson will update that instead of creating a new one as usually:
Store store = context.getBean(Store.class);
objectMapper.readerForUpdating(store).readValue("{\"name\":\"myStore\"}");
Where context is a Spring ApplicationContext reference that I autowired in a test class. You don't need to use the return value of readValue in this case, just inspect the existing store variable and name will be updated.
Java Spring question:
I have a interface MyInterface with one method
void exec (String str);
I have many implementation of MyInterface, say Oneimpl, anotherimpl yetanotherimpl...and so on and can keep adding new implementations.
how do I obtain an instance of a specific implementation using just the name of the implementing class passed as a STRING value , say "someRandomImpl"
The code should be dynamic and can provide a instance of new implementations without code change.
implements ApplicationContextAware
it will autowired ApplicationContext object
use the object like
context.getBean(beanName)
then you get the bean
I am interested to inject a bean reference, which is resolved based on another property on the same bean:
#Autowired
#Qualifier("#{'prefix' + actualQualifier}")
private OtherBean otherBean
private String actualQualifier;
This would ensure that the relationship between "actualQualifier" and "otherBean" is correct.
There is a number of beans configured of the type OtherBean.
I can make sure that "actualQualifier" has a value set before autowiring/injection begins.
I am unable to find any way to reference another property value (in the JavaBean sense) on the same bean that is currently being autowired.
AFAIK, this will not work. SpEL has no access to variables of the enclosing class. And anyway, it looks like #Qualifier does not process SpEL expressions.
I did some tests and never found how to use a SpEL expression as a #Qualifier value. This page from Spring forums (and the error messages from Spring) let me think that in fact #Qualifier only takes a String and does not try to evaluate a SpEL expression.
My conclusion is that way will lead you in a dead end.
As suggested in this other answer, I think you'd better use a selector bean and set otherBean in an init method :
#Bean(initMethod="init")
class MyBean {
...
#Autowired
private BeanSelector beanSelector;
private OtherBean otherBean
private String actualQualifier;
public void init() {
otherBean = beanSelector(actualQualifier);
}
...
}
and put all intelligence about the choice of otherBean in beanSelector.
I have a bean with final field.
public class Foo {
Service service;
final String bar;
public Foo(String bar){};
}
service is not final and has a setter. bar is final and can have many values. I cannot remove the final keyword. I try to create a spring factory that allows to create Foo's instances with injected service and dynamic bar value. factory.create(bar). Foo beans are instanciated at runtime because bar value is not known and unbounded
I have try:
#Configuration, but configuration does not allow parameters not managed by spring or dynamic parameter.
Lookup method needs a no-arg constructor.
Any idea ?
Thanks!
Take a look at ApplicationContext.getBean(String name, Object... args) method. You can pass arguments to bean creation with args parameter.
You can use constructor injection in the Application Context XML as one way to do this:
<bean name="foo" class="com.example.Foo">
<constructor-arg index="0">Bar</constructor-arg>
</bean>
EDIT: Missed that, check out this question: How to use #Autowired in spring
The second answer (not by me)
It looks like you might be able to use #Configurable annotation here.
My spring bean have a constructor with an unique mandatory argument, and I managed to initialize it with the xml configuration :
<bean name="interfaceParameters#ota" class="com.company.core.DefaultInterfaceParameters">
<constructor-arg>
<value>OTA</value>
</constructor-arg>
</bean>
Then I use this bean like this and it works well.
#Resource(name = "interfaceParameters#ota")
private InterfaceParameters interfaceParameters;
But I would like to specify the contructor arg value with the annocations, something like
#Resource(name = "interfaceParameters#ota")
#contructorArg("ota") // I know it doesn't exists!
private InterfaceParameters interfaceParameters;
Is this possible ?
Thanks in advance
First, you have to specify the constructor arg in your bean definition, and not in your injection points. Then, you can utilize spring's #Value annotation (spring 3.0)
#Component
public class DefaultInterfaceParameters {
#Inject
public DefaultInterfaceParameters(#Value("${some.property}") String value) {
// assign to a field.
}
}
This is also encouraged as Spring advises constructor injection over field injection.
As far as I see the problem, this might not suit you, since you appear to define multiple beans of the same class, named differently. For that you cannot use annotations, you have to define these in XML.
However I do not think it is such a good idea to have these different beans. You'd better use only the string values. But I cannot give more information, because I dont know your exact classes.
As Bozho said, instead of constructor arg you could set the property...#PostConstruct will only get called after all the properties are set...so, you will still have your string available ...