How to read values from properties file?

Configure PropertyPlaceholder in your context:

<context:property-placeholder location="classpath*:my.properties"/>

Then you refer to the properties in your beans:

@Component
class MyClass {
  @Value("${my.property.name}")
  private String[] myValues;
}

To parse property with multiple comma-separated values:

my.property.name=aaa,bbb,ccc

If that doesn't work, you can define a bean with properties, inject and process it manually:

<bean id="myProperties"
      class="org.springframework.beans.factory.config.PropertiesFactoryBean">
  <property name="locations">
    <list>
      <value>classpath*:my.properties</value>
    </list>
  </property>
</bean>

and the bean:

@Component
class MyClass {
  @Resource(name="myProperties")
  private Properties myProperties;

  @PostConstruct
  public void init() {
    // do whatever you need with properties
  }
}

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There are various ways to achieve the same. Below are some commonly used ways in spring-

Using PropertyPlaceholderConfigurer Using PropertySource Using ResourceBundleMessageSource Using PropertiesFactoryBean and many more........................

Assuming ds.type is key in your property file.

Using PropertyPlaceholderConfigurer

Register PropertyPlaceholderConfigurer bean-

<context:property-placeholder location="classpath:path/filename.properties"/>

or

<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
  <property name="locations" value="classpath:path/filename.properties" ></property>
</bean>

or

@Configuration
public class SampleConfig {
 @Bean
 public static PropertySourcesPlaceholderConfigurer placeHolderConfigurer() {
  return new PropertySourcesPlaceholderConfigurer();
  //set locations as well.
 }
}

After registering PropertySourcesPlaceholderConfigurer, you can access the value-

@Value("${ds.type}")private String attr; 

Using PropertySource

In the latest spring version you don't need to register PropertyPlaceHolderConfigurer with @PropertySource, I found a good link to understand version compatibility-

@PropertySource("classpath:path/filename.properties")
@Component
public class BeanTester {
    @Autowired Environment environment; 
    public void execute() {
        String attr = this.environment.getProperty("ds.type");
    }
}

Using ResourceBundleMessageSource

Register Bean-

<bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
  <property name="basenames">
    <list>
      <value>classpath:path/filename.properties</value>
    </list>
  </property>
</bean>

Access Value-

((ApplicationContext)context).getMessage("ds.type", null, null);

or

@Component
public class BeanTester {
    @Autowired MessageSource messageSource; 
    public void execute() {
        String attr = this.messageSource.getMessage("ds.type", null, null);
    }
}

Using PropertiesFactoryBean

Register Bean-

<bean id="properties"
      class="org.springframework.beans.factory.config.PropertiesFactoryBean">
  <property name="locations">
    <list>
      <value>classpath:path/filename.properties</value>
    </list>
  </property>
</bean>

Wire Properties instance into your class-

@Component
public class BeanTester {
    @Autowired Properties properties; 
    public void execute() {
        String attr = properties.getProperty("ds.type");
    }
}

---

In configuration class

@Configuration
@PropertySource("classpath:/com/myco/app.properties")
public class AppConfig {
   @Autowired
   Environment env;

   @Bean
   public TestBean testBean() {
       TestBean testBean = new TestBean();
       testBean.setName(env.getProperty("testbean.name"));
       return testBean;
   }
}

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Here is an additional answer that was also great help for me to understand how it worked : http://www.javacodegeeks.com/2013/07/spring-bean-and-propertyplaceholderconfigurer.html

any BeanFactoryPostProcessor beans have to be declared with a static, modifier

@Configuration
@PropertySource("classpath:root/test.props")
public class SampleConfig {
 @Value("${test.prop}")
 private String attr;
 @Bean
 public SampleService sampleService() {
  return new SampleService(attr);
 }

 @Bean
 public static PropertySourcesPlaceholderConfigurer placeHolderConfigurer() {
  return new PropertySourcesPlaceholderConfigurer();
 }
}

---

If you need to manually read a properties file without using @Value.

Thanks for the well written page by Lokesh Gupta : Blog

https://i.stack.imgur.com/BUczm.png

package utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.ResourceUtils;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import java.io.File;


public class Utils {

    private static final Logger LOGGER = LoggerFactory.getLogger(Utils.class.getName());

    public static Properties fetchProperties(){
        Properties properties = new Properties();
        try {
            File file = ResourceUtils.getFile("classpath:application.properties");
            InputStream in = new FileInputStream(file);
            properties.load(in);
        } catch (IOException e) {
            LOGGER.error(e.getMessage());
        }
        return properties;
    }
}

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Another way is using a ResourceBundle. Basically you get the bundle using its name without the '.properties'

private static final ResourceBundle resource = ResourceBundle.getBundle("config");

And you recover any value using this:

private final String prop = resource.getString("propName");

---

You need to put a PropertyPlaceholderConfigurer bean in your application context and set its location property.

See details here : http://www.zparacha.com/how-to-read-properties-file-in-spring/

You might have to modify your property file a bit for this thing to work.

Hope it helps.

---

I wanted an utility class which is not managed by spring, so no spring annotations like @Component, @Configuration etc. But I wanted the class to read from application.properties

I managed to get it working by getting the class to be aware of the Spring Context, hence is aware of Environment, and hence environment.getProperty() works as expected.

To be explicit, I have:

application.properties

mypath=somestring

Utils.java

import org.springframework.core.env.Environment;

// No spring annotations here
public class Utils {
    public String execute(String cmd) {
        // Making the class Spring context aware
        ApplicationContextProvider appContext = new ApplicationContextProvider();
        Environment env = appContext.getApplicationContext().getEnvironment();

        // env.getProperty() works!!!
        System.out.println(env.getProperty("mypath")) 
    }
}

ApplicationContextProvider.java (see Spring get current ApplicationContext)

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

@Component
public class ApplicationContextProvider implements ApplicationContextAware {
    private static ApplicationContext CONTEXT;

    public ApplicationContext getApplicationContext() {
        return CONTEXT;
    }

    public void setApplicationContext(ApplicationContext context) throws BeansException {
        CONTEXT = context;
    }

    public static Object getBean(String beanName) {
        return CONTEXT.getBean(beanName);
    }
}

---

 [project structure]: http://i.stack.imgur.com/RAGX3.jpg
-------------------------------
    package beans;

        import java.util.Properties;
        import java.util.Set;

        public class PropertiesBeans {

            private Properties properties;

            public void setProperties(Properties properties) {
                this.properties = properties;
            }

            public void getProperty(){
                Set keys = properties.keySet();
                for (Object key : keys) {
                    System.out.println(key+" : "+properties.getProperty(key.toString()));
                }
            }

        }
    ----------------------------

        package beans;

        import org.springframework.context.ApplicationContext;
        import org.springframework.context.support.ClassPathXmlApplicationContext;

        public class Test {

            public static void main(String[] args) {
                // TODO Auto-generated method stub
                ApplicationContext ap = new ClassPathXmlApplicationContext("resource/spring.xml");
                PropertiesBeans p = (PropertiesBeans)ap.getBean("p");
                p.getProperty();
            }

        }
    ----------------------------

 - driver.properties

    Driver = com.mysql.jdbc.Driver
    url = jdbc:mysql://localhost:3306/test
    username = root
    password = root
    ----------------------------



     <beans xmlns="http://www.springframework.org/schema/beans"
               xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
               xmlns:util="http://www.springframework.org/schema/util"
               xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd">

            <bean id="p" class="beans.PropertiesBeans">
                <property name="properties">
                    <util:properties location="classpath:resource/driver.properties"/>
                </property>
            </bean>

        </beans>

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I'll recommend reading this link https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-external-config.html from SpringBoot docs about injecting external configs. They didn't only talk about retrieving from a properties file but also YAML and even JSON files. I found it helpful. I hope you do too.

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