Null Pointer Exception Spring Autowired in JavaFX

Question

I am trying to autowire my datamodel class into various controller classes using the Autowired annotation and I keep getting a null pointer exception, I would like to keep my configuration XML based and avoid using the application context implementation if possible. a snippet of the code and spring-config file is below

Spring-Config

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-2.5.xsd">

    <context:annotation-config/>

    <bean id="datamodel" class="com.filemanager.datamodel.DataModel" autowire="byType"/>

</beans>

Data Model Class

public class DataModel {

    private ObservableList<Song> windowDisplaySongs;

    public void test() {
        System.out.println("Hey, this is working");
    }

    public ObservableList<Song> getWindowDisplaySongs() {
        return windowDisplaySongs;
    }
    public void setWindowDisplaySongs(ObservableList<Song> windowDisplaySongs) {
        this.windowDisplaySongs = windowDisplaySongs;
    }
}

Controller that has dependency on Model

public class FileBrowserController implements Initializable {

    @Autowired
    DataModel dataModel;

    @Override
    public void initialize(URL location, ResourceBundle resources) {

        dataModel.test();
    }
}

Things that I have tried

Using the component annotation above the model class, and above the model and controller class
Using the controller annotation above the controller class
Renaming the datamodel reference to match the name within the spring-config file
Using the qualifier annotation to specify that the datamodel reference should match the name in the spring config file.
Using the model reference in a method other than the init method
Removing the autowire="byType" from the config file
Creating an application context in the main method by using the code below, I was able to use the getBean() method with this, but I would like to use autowired to automatically inject the dependencies instead of having to call the getBean() method each time.
```
ApplicationContext ctx = new ClassPathXmlApplicationContext("config/spring-config.xml");
```
Following the solutions to other null pointer spring issues already on Stackoverflow:

score 1 · Answer 1 · answered Apr 11 '18 at 08:47

1

The FileBrowserController class should be annotated as @Controller so spring knows it should inject properties there. Also @Autowiring without qualifier checks if you have a bean with the name of the property. In your case:

@Autowired
DataModel dataModel;

Check for bean with id dataModel but your bean is defined with different name :

<bean id="datamodel"...

Spot the difference? :) you can either change the bean id or you can use Qualifier to make it even clearer

@Autowired
@Qualifier("datamodel")
DataModel dataModel;

answered Apr 11 '18 at 08:47

Veselin Davidov

7,031
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Thank you for your I help, however, I tried the solution and still didn't have any luck but just for a little clarification, isn't the controller annotation the same as the component annotation? I was always under the impression that component was basically the generic stereotype and the controller, service, and repository stereotypes were more specialized but they all accomplished the same thing? – oznomal Apr 11 '18 at 09:19

Null Pointer Exception Spring Autowired in JavaFX

1 Answers1