spring annotations i never had the chance to use part 2: @ConfigurationProperties

Few days ago, I accidentally stumbled upon a Spring annotation from Spring Boot project while I was checking something else.

We all know how to bind property values with "@Value" to the classes and we all know that this can be quite cumbersome if there are multiple properties to bind. Spring Boot is here to help. You can use "@ConfigurationProperties" and bind multiple values quite concisely. We will give a prefix to differentiate other configs from ours. e.g. "@ConfigurationProperties(prefix = "jdbc")".
Any field this annotated class has is populated with property values from the property resource. For instance if it has a username parameter then property resource with "jdbc.username" key will populate this field. The most practical way of using this annotation is using it with "@Configuration".


You can check how we create the config class.

package com.sezinkarli.tryconfigprops;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Configuration;

import javax.annotation.PostConstruct;
import java.util.HashMap;
import java.util.Map;

@Configuration
@ConfigurationProperties(prefix = "jdbc")
public class JdbcConfig
{
    private String user;
    private String password;
    private String url;
    private String driver;

    public String getUser()
    {
        return user;
    }

    public void setUser(String user)
    {
        this.user = user;
    }

    public String getPassword()
    {
        return password;
    }

    public void setPassword(String password)
    {
        this.password = password;
    }

    public String getUrl()
    {
        return url;
    }

    public void setUrl(String url)
    {
        this.url = url;
    }

    public String getDriver()
    {
        return driver;
    }

    public void setDriver(String driver)
    {
        this.driver = driver;
    }

    public String getProperty(String key)
    {
        return propertyMap.get(key);
    }
}

And below you can check the properties we map from application properties

jdbc.user=myJdbcUser
jdbc.password=myPwd
jdbc.url=myUrl
jdbc.driver=myJdbcDriver

After that you can easily get these values by injecting the configuration class to somewhere.

@Service
public class YourService
{

    @Autowired
    private JdbcConfig jdbcConfig;
}

You can also check here for a working toy project using "@ConfigurationProperties".

mongodb default configuration in spring boot

I'm trying to integrate mongodb to my spring boot application. I create a db aptly named "mydb" and was wondering how mongodb classes were able to connect to my database without any configuration and why they were not retrieving my data. Answer to both is of course "default configuration" for mongodb.

You can see mongodb defaults that spring boot uses:

host: localhost
port: 27017
db: test

My mongodb is at localhost:27017, but as I'm using "mydb" instead of "test" no data is retrieved. So I have to override the default configuration by adding

spring.data.mongodb.uri=mongodb://localhost:27017/mydb

to my application.properties file.