I am trying to retrofit Spring DI into an existing application using Spring Boot. I want to use JSR-330 annotations instead of Spring's. I would like to make prototype scope the default so I don't have to use non-JSR-330 scope #Scope("prototype") everywhere. I first tried to install the JSR330ScopeMetadataResolver using:
SpringApplication application = new SpringApplication(OurApplication.class);
ConfigurableApplicationContext context = application.createContext();
context..setScopeMetadataResolver(new Jsr330ScopeMetadataResolver());
application.run(args);
I still get a singleton when injecting a class with no annotation. I then tried using an ApplicationContextInitializer to do the same thing. Either way, I get a singleton injected. In the debugger, I verified with the initializer that Jsr330ScopeMetadataResolver is getting set in the ApplicationContext. In the Jsr330ScopeMetadataResolver instance, I see a map is getting populated in the default constructor with key /value as singleton. I obviously are missing something. Does anyone know what that is?
We finally were able to figure this out. The solution was:
private static final String CONTEXT_PACKAGES_TO_SCAN =
"my.company.package.*";
public static void main(String[] args) {
SpringApplication application = new SpringApplication(
MainApplication.class);
application.addInitializers(new Jsr330Initializer());
application.run(args);
}
public static class Jsr330Initializer implements
ApplicationContextInitializer<AnnotationConfigApplicationContext>
{
#Override
public void initialize(AnnotationConfigApplicationContext context) {
context.setScopeMetadataResolver(new Jsr330ScopeMetadataResolver());
context.scan(CONTEXT_PACKAGES_TO_SCAN);
}
}
The key is to perform context.scan() in the initializer. Packages to scan must end in ".*", or the main application gets added twice and Spring fails to start.
Related
I am trying to create a lightweight web service around a legacy java library to expose it as a web service using Spring Boot. I am new to Spring, while I have a lot of java experiance writing libraries all my web service experiance is in ASP.NET.
I can instantiate an instance of my library object but I can't figure out how to then have that object be injected into my controllers via #Autowired when the application is spun up.
This is my main application:
#SpringBootApplication
public class ResolverWebServiceApplication {
private static ArgumentParser newArgumentParser() {
ArgumentParser parser = ArgumentParsers.newFor("Resolver").build();
// configuring the parser
return parser;
}
public static void main(String[] args) throws ArgumentParserException {
ArgumentParser parser = newArgumentParser();
Namespace ns = parser.parseArgs(args);
ResolverOptions options = new ResolverOptions.Builder(ns)
.build();
ResolverContext context = new ResolverContext(options);
// ^^^ I need to get this injected into my controllers ^^^
SpringApplication.run(ResolverWebServiceApplication.class, args);
}
}
And then a simple controller which needs the class injected:
#RestController
public class VersionController {
#Autowired
private ResolverContext context; // And here the instance needs to be injected.
#GetMapping(path = "/version", produces = MediaType.APPLICATION_JSON_VALUE)
public long version() {
return context.getResolver().getVersionAsLong();
}
}
I could make the context a singleton which the controllers just refer to but I want to be able to test my controllers by mocking the context. There is also obviously a lot of validation and error handeling that needs to be added.
I can't have it be a Bean since I only want to instantiate one for my entire application.
The closest question I have found is this one: Registering an instance as 'singleton' bean at application startup. But I can't put the options in the configuration files. The application might be spun up in a container or on a users machine and requires the ability to accept arguments to initialize the library class. It would be a real usability degradation if someone had to manually edit the application config for these options.
You need to tell spring to consider the required classes from your lib when initializing the application context i.e Configure and let spring know how to create a bean and then let spring handle dependency injection for you.
First of all, add required jar that you have in your build file, say pom.xml for maven, in your current project. Idea is to have it on your classpath when you build the project.
As you said it is legacy lib and I am assuming it is not a spring bean, then
In your configuration class, return it as a bean, using #Bean annotaion.
#Configuration
public class YourConfigurationClass {
#Bean
SomeBean returnSomeBeanFromLegacyLib() {
return new SomeClassFromLib();
}
Once you return this bean from your config, it should be available to Spring Context for dependency injection whereever you #Autowire the required dependency.
#SpringBootApplication
public class MainApplication {
#Autowired
static BibliographyIndexer bi;
public static void main(String[] args) {
SpringApplication.run(MainApplication.class, args);
bi.reindex();
}
}
#Repository
public class BibliographyIndexer {
...
}
Whenever I access the properties of bi I get a NullPointerException. I know the #Autowired notation didn't work. But why?
Note: both classes are under the same package.
Additional question: Since I want to run a method upon the start of the spring application. Is this the best approach since #pepevalbe's answer already gave me the workaround I needed. Is there another way to run a method upon the start of the spring application?
Because you can't #Autorwire an static class. It doesn't get initialized so you get a NPE when trying to use it.
There are workarounds to wire a bean into a static class, but it is strongly discouraged.
EDIT:
If you need to execute code after initilization you could add an event listener:
#SpringBootApplication
public class MainApplication {
#Autowired
BibliographyIndexer bi;
public static void main(String[] args) {
SpringApplication.run(MainApplication.class, args);
}
#EventListener(ApplicationReadyEvent.class)
public void doAfterStartUp() {
bi.reindex();
}
}
There are several reasons #Autowired might not work.
When a new instance is created not by Spring but by for example manually calling a constructor, the instance of the class will not be registered in the Spring context and thus not available for dependency injection. Also when you use #Autowired in the class of which you created a new instance, the Spring context will not be known to it and thus most likely this will also fail.
Another reason can be that the class you want to use #Autowired in, is not picked up by the ComponentScan. This can basically be because of two reasons.
The package is outside the ComponentScan search path. Move the package to a scanned location or configure the ComponentScan to fix this.
The class in which you want to use #Autowired does not have a Spring annotation. Add one of the following annotatons to the class: #Component, #Repository, #Service, #Controller, #Configuration. They have different behaviors so choose carefully........
Your problem is that you cannot use bi in main because main is static.
Making bi static doesn't help because static fields will not be #Autowired (It is possible but does not make sense in the concepts of Dependency Injection).
Remove static and move bi.reindex() to a new method annotated with #PostConstruct. It will be executed after the MainApplication-bean is fully initialized and here you can use your injected bi.
In main method you can refer to context and from it get access to bean BibliographyIndexer. In static main spring can not creates and injects bean so this is how you can get it from context.
public static void main(String[] args) {
ApplicationContext context = SpringApplication.run(MainApplication.class, args);
BibliographyIndexer bibliographyIndexer = context.getBean(BibliographyIndexer.class);
bibliographyIndexer.reindex();
}
You can also do as in answer from pepevalbe and execute this code after initialization.
I implemented spring-boot application and now I want to use it as a lib for non-spring application.
How can I initialize lib classes so autowired dependencies work as expected?Obviously if I create class instance with 'new', all autowired dependencies will be null.
The theory is that you need to instantiate an application context for your Spring Boot dependency to live in, then extract a bean from there and make use of it.
In practice, in your Spring Boot dependency you should have an Application.java class or similar, in which a main method starts the application. Start by adding there a method like this:
public static ApplicationContext initializeContext(final String[] args) {
return SpringApplication.run(Application.class, args);
}
Next step, in you main application, when you see fit (I'd say during startup but might as well be the first time you need to use your dependency) you need to run this code:
final String[] args = new String[0]; // configure the Spring Boot app as needed
final ApplicationContext context = Application.initializeContext(args); // createSpring application context
final YourBean yourBean = (YourBean)context.getBean("yourBean"); // get a reference of your bean from the application context
From here you can use your beans as you see fit.
I'm not sure how you will handle to wait until the context is fully loaded before you try to access some beans from your Constructor etc. But if you just want to access context without creating components manually try one of those:
1) Simply Inject ApplicationContext
#Inject
private ApplicationContext context;
or
2) Implement ApplicationContextAware
public class ApplicationContext implements ApplicationContextAware {
private ApplicationContext context;
#Override
public void setApplicationContext(ApplicationContext context) {
this.context = context;
}
// just quick example, better to set it to your custom singleton class
public static ApplicationContext getContext() {
return context;
}
}
Then use context.getBean(SomeServiceFromLibrary.class);
I am trying to get Quartz working with Spring Boot, and am not managing to get the injection working correctly. I am basing myself on the example shown here
Here is my boot class:
#ComponentScan
#EnableAutoConfiguration
public class MyApp {
#Autowired
private DataSource dataSource;
#Bean
public JobFactory jobFactory() {
return new SpringBeanJobFactory();
}
#Bean
public SchedulerFactoryBean quartz() {
final SchedulerFactoryBean bean = new SchedulerFactoryBean();
bean.setJobFactory(jobFactory());
bean.setDataSource(dataSource);
bean.setConfigLocation(new ClassPathResource("quartz.properties"));
...
return bean;
}
public static void main(String[] args) {
SpringApplication.run(MyApp.class, args);
}
}
When the quartz() method is invoked by Spring, dataSource is null. However, if I change the return type of the quartz() method to Object, dataSource is correctly injected with the datasource created by reading application.properties, the bean is built, everything works and I get a subsequent error saying that Quartz has been unable to retrieve any jobs from the database, which is normal as I haven't put the schema in place yet.
I have tried adding a #DependsOn("dataSource") annotation on the quartz() method but that doesn't make any difference.
This class is the only class annotated with #Configuration.
Here are my dependencies (I'm using Maven but present them like this for space reasons):
org.springframework.boot:spring-boot-starter-actuator:1.0.0.RC4
org.springframework.boot:spring-boot-starter-jdbc:1.0.0.RC4
org.springframework.boot:spring-boot-starter-web:1.0.0.RC4
org.quartz-scheduler:quartz:2.2.1
org.springframework:spring-support:2.0.8
And the parent:
org.springframework.boot:spring-boot-starter-parent:1.0.0.RC4
Finally the content of quartz.properties:
org.quartz.threadPool.threadCount = 3
org.quartz.jobStore.class=org.springframework.scheduling.quartz.LocalDataSourceJobStore
org.quartz.jobStore.driverDelegateClass=org.quartz.impl.jdbcjobstore.PostgreSQLDelegate
What am I doing wrong?
(I have seen this question, but that question initialises the datasource in the #Configuration class)
Your app starts up (with a schema error, which is expected) if I use "org.springframework:spring-context-support:4.0.2.RELEASE" ("org.springframework:spring-support:2.0.8" if it ever existed must be nearly 10 years old now and certainly isn't compatible with Boot or Quartz 2).
I have a web application with spring 3.0. I need to run a class with main method from a cron that uses beans defined in appcontext xml(using component scan annocations). I have my main class in same src directory.
How can I inject beans from web context into main method. I tried to do it using
ApplicationContext context = new ClassPathXmlApplicationContext("appservlet.xml");
I tried to use AutoWired and it returns a null bean. So I used Application ctx and this is creating a new context (as expected) when I run main method. But is it possible that I can use existing beans from container.
#Autowired
static DAO dao;
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("xman- servlet.xml");
TableClient client = context.getBean(TableClient.class);
client.start(context);
}
You can not inject a Spring bean into any object that was not created by spring. Another way to say that is: Spring can only inject into objects that it manages.
Since you are creating the context, you will need to call getBean for your DAO object.
Check out Spring Batch it may be useful to you.
You may use a spring context for your main application, and reuse the same beans as the webapp. You could even reuse some Spring XML configuration files, provided they don't define beans which only make sense in a webapp context (request-scope, web controllers, etc.).
But you'll get different instances, since you'll have two JVMs running. If you really want to reuse the same bean instances, then your main class should remotely call some method of a bean in your webapp, using a web service, or HttpInvoker.
Try with this Main:
public class Main {
public static void main(String[] args) {
Main p = new Main();
p.start(args);
}
#Autowired
private MyBean myBean;
private void start(String[] args) {
ApplicationContext context =
new ClassPathXmlApplicationContext("classpath*:/META-INF/spring/applicationContext*.xml");
System.out.println("The method of my Bean: " + myBean.getStr());
}
}
And this Bean:
#Service
public class MyBean {
public String getStr() {
return "mybean!";
}
}
In order to address this issue, I have created https://jira.springsource.org/browse/SPR-9044. If you like the proposed approach, please vote for it.
Spring boot provides an official solution for this. Download a skeleton from
https://start.spring.io/
and make sure packaging in the pom.xml is set to jar. As long as you don't include any web dependency the application will remain a console app.