问题
I have a Spring-Boot-Application as a multimodule-Project in maven. The structure is as follows:
Parent-Project
|--MainApplication
|--Module1
|--ModuleN
In the MainApplication project there is the main() method class annotated with @SpringBootApplication and so on. This project has, as always, an application.properties file which is loaded automatically. So I can access the values with the @Value annotation
@Value("${myapp.api-key}")
private String apiKey;
Within my Module1 I want to use a properties file as well (called module1.properties), where the modules configuration is stored. This File will only be accessed and used in the module. But I cannot get it loaded. I tried it with @Configuration and @PropertySource but no luck.
@Configuration
@PropertySource(value = "classpath:module1.properties")
public class ConfigClass {
How can I load a properties file with Spring-Boot and access the values easily? Could not find a valid solution.
My Configuration
@Configuration
@PropertySource(value = "classpath:tmdb.properties")
public class TMDbConfig {
@Value("${moviedb.tmdb.api-key}")
private String apiKey;
public String getApiKey() {
return apiKey;
}
@Bean
public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
return new PropertySourcesPlaceholderConfigurer();
}
}
Calling the Config
@Component
public class TMDbWarper {
@Autowired
private TMDbConfig tmdbConfig;
private TmdbApi tmdbApi;
public TMDbWarper(){
tmdbApi = new TmdbApi(tmdbConfig.getApiKey());
}
I'm getting an NullPointerException in the constructor when I autowire the warper.
回答1:
For field injection:
Fields are injected right after construction of a bean, before any config methods are invoked. Such a config field does not have to be public. Refer Autowired annotation for complete usage. Use constructor injection in this case like below:
@Component
public class TMDbWarper {
private TMDbConfig tmdbConfig;
private TmdbApi tmdbApi;
@Autowired
public TMDbWarper(final TMDbConfig tmdbConfig){
this.tmdbConfig = tmdbConfig;
tmdbApi = new TmdbApi(tmdbConfig.getApiKey());
}
(or)
Use @PostConstruct to initialise like below:
@Component
public class TMDbWarper {
@Autowired
private TMDbConfig tmdbConfig;
private TmdbApi tmdbApi;
@PostConstruct
public void init() {
// any initialisation method
tmdbConfig.getConfig();
}
回答2:
Autowiring is performed just after the creation of the object(after calling the constructor via reflection). So NullPointerException is expected in your constructor as tmdbConfig field would be null during invocation of constructor
You may fix this by using the @PostConstruct callback method as shown below:
@Component
public class TMDbWarper {
@Autowired
private TMDbConfig tmdbConfig;
private TmdbApi tmdbApi;
public TMDbWarper() {
}
@PostConstruct
public void init() {
tmdbApi = new TmdbApi(tmdbConfig.getApiKey());
}
public TmdbApi getTmdbApi() {
return this.tmdbApi;
}
}
Rest of your configuration seems correct to me.
Hope this helps.
回答3:
Here is a Spring Boot multi-module example where you can get properties in different module. Let's say I have main application module, dataparse-module, datasave-module.
StartApp.java in application module:
@SpringBootApplication
public class StartApp {
public static void main(String[] args) {
SpringApplication.run(StartApp.class, args);
}
}
Configuration in dataparse-module. ParseConfig.java:
@Configuration
public class ParseConfig {
@Bean
public XmlParseService xmlParseService() {
return new XmlParseService();
}
}
XmlParseService.java:
@Service
public class XmlParseService {...}
Configuration in datasave-module. SaveConfig.java:
@Configuration
@EnableConfigurationProperties(ServiceProperties.class)
@Import(ParseConfig.class)//get beans from dataparse-module - in this case XmlParseService
public class SaveConfig {
@Bean
public SaveXmlService saveXmlService() {
return new SaveXmlService();
}
}
ServiceProperties.java:
@ConfigurationProperties("datasave")
public class ServiceProperties {
private String message;
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
}
application.properties in datasave-module in resource/config folder:
datasave.message=Multi-module Maven project!
threads.xml.number=5
file.location.on.disk=D:\temp\registry
Then in datasave-module you can use all your properties either through @Value.
SaveXmlService.java:
@Service
public class SaveXmlService {
@Autowired
XmlParseService xmlParseService;
@Value("${file.location.on.disk: none}")
private String fileLocation;
@Value("${threads.xml.number: 3}")
private int numberOfXmlThreads;
...
}
Or through ServiceProperties:
Service.java:
@Component
public class Service {
@Autowired
ServiceProperties serviceProperties;
public String message() {
return serviceProperties.getMessage();
}
}
回答4:
I had this situation before, I noticed that the properties file was not copied to the jar.
I made the following to get it working:
In the resources folder, I have created a unique package, then stored my application.properties file inside it. e.g: com/company/project
In the configuration file e.g: TMDBConfig.java I have referenced the full path of my .properties file:
@Configuration @PropertySource("classpath:/com/company/project/application.properties") public class AwsConfig
Build and run, it will work like magic.
回答5:
You could autowire and use the Enviornment bean to read the property
@Configuration
@PropertySource(value = "classpath:tmdb.properties")
public class TMDbConfig {
@Autowired
private Environment env;
public String getApiKey() {
return env.getRequiredProperty("moviedb.tmdb.api-key");
}
}
This should guarantee that property is read from the context when you invoke the getApiKey() method regardless of when the @Value expression is resolved by PropertySourcesPlaceholderConfigurer.
来源：https://stackoverflow.com/questions/46784051/spring-boot-multi-module-project-load-property-file