Spring @PropertySource example
In Spring, you can use @PropertySource annotation to externalize your configuration to a properties file. In this tutorial, we will show you how to use @PropertySource to read a properties file and display the values with @Value and Environment.
P.S @PropertySource has been available since Spring 3.1
1. @PropertySource and @Value
A classic example, read a properties file and display with ${}.
config.properties
mongodb.url=1.2.3.4 mongodb.db=hello
AppConfigMongoDB
package com.mkyong.config; import org.springframework.beans.factory.annotation.Value; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.PropertySource; import org.springframework.context.support.PropertySourcesPlaceholderConfigurer; //... @Configuration @ComponentScan(basePackages = { "com.mkyong.*" }) @PropertySource("classpath:config.properties") public class AppConfigMongoDB { //1.2.3.4 @Value("${mongodb.url}") private String mongodbUrl; //hello @Value("${mongodb.db}") private String defaultDb; @Bean public MongoTemplate mongoTemplate() throws Exception { MongoClientOptions mongoOptions = new MongoClientOptions.Builder().maxWaitTime(1000 * 60 * 5).build(); MongoClient mongo = new MongoClient(mongodbUrl, mongoOptions); MongoDbFactory mongoDbFactory = new SimpleMongoDbFactory(mongo, defaultDb); return new MongoTemplate(mongoDbFactory); //To resolve ${} in @Value @Bean public static PropertySourcesPlaceholderConfigurer propertyConfigInDev() { return new PropertySourcesPlaceholderConfigurer();
Note
To resolve ${} in @Values, you must register a static PropertySourcesPlaceholderConfigurer in either XML or annotation configuration file.
2. @PropertySource and Environment
Spring recommends to use Environment to get the property values.
AppConfigMongoDB
package com.mkyong.config; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.PropertySource; import org.springframework.core.env.Environment; //... @Configuration @ComponentScan(basePackages = { "com.mkyong.*" }) @PropertySource("classpath:config.properties") public class AppConfigMongoDB { @Autowired private Environment env; @Bean public MongoTemplate mongoTemplate() throws Exception { String mongodbUrl = env.getProperty("mongodb.url"); String defaultDb = env.getProperty("mongodb.db"); MongoClientOptions mongoOptions = new MongoClientOptions.Builder().maxWaitTime(1000 * 60 * 5).build(); MongoClient mongo = new MongoClient(mongodbUrl, mongoOptions); MongoDbFactory mongoDbFactory = new SimpleMongoDbFactory(mongo, defaultDb); return new MongoTemplate(mongoDbFactory);
3. More @PropertySource Examples
More common examples.
3.1 Example to resolve ${} within @PropertySource resource locations.
@Configuration @PropertySource("file:${app.home}/app.properties") public class AppConfig { @Autowired Environment env;
Set a system property during startup.
System.setProperty("app.home", "test"); java -jar -Dapp.home="/home/mkyon/test" example.jar
3.2 Include multiple properties files.
@Configuration @PropertySource({ "classpath:config.properties", "classpath:db.properties" //if same key, this will 'win' }) public class AppConfig { @Autowired Environment env;
Note
If a property key is duplicated, the last declared file will ‘win’ and override.
4. Spring 4 and @PropertySources
Some enhancements on Spring 4.
4.1 Introduces new @PropertySources to support Java 8 and better way to include multiple properties files.
@Configuration @PropertySources({ @PropertySource("classpath:config.properties"), @PropertySource("classpath:db.properties") }) public class AppConfig { //...
4.2 Allow @PropertySource to ignore the not found properties file.
@Configuration @PropertySource("classpath:missing.properties") public class AppConfig { //...
If missing.properties is not found, the system is unable to start and throws FileNotFoundException
Caused by: java.io.FileNotFoundException: class path resource [missiong.properties] cannot be opened because it does not exist
In Spring 4, you can use ignoreResourceNotFound to ignore the not found properties file
@Configuration @PropertySource(value="classpath:missing.properties", ignoreResourceNotFound=true) public class AppConfig { //...
@PropertySources({ @PropertySource(value = "classpath:missing.properties", ignoreResourceNotFound=true), @PropertySource("classpath:config.properties") })
Done.
References
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