4 ways to read configuration in Spring Boot, recommended to collect!

In Spring Boot projects, reading the contents of configuration files is basically involved. This article will talk about several common ways to read configuration files.

Value annotation

In application.propertiesConfiguration file configuration item:

name=tian

Read in java code:

/**
 * @author tianwc  公众号：java后端技术全栈、面试专栏
 * @version 1.0.0
 * @date 2023年07月02日 21:00
 * 博客地址：<a href="http://woaijava.cc/">博客地址</a>
 */
@RestController
@RequestMapping("/configuration")
public class ConfigurationController {

    @Value("${name}")
    private String name;

    @GetMapping("/index")
    public String test() {
        return name;
    }
}

Verify:

GET

http://localhost:8089/configuration/index

Return parameters:

tian

This type usually does not have a prefix, and single configuration items will be read in this way.

If there is the same prefix configuration, then we can use the following method.

ConfigurationProperties annotation

In application.propertiesConfiguration file configuration items:

user.userName=tian1
user.age=21

In javadiam Read in:

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

/**
 * @author tianwc  公众号：java后端技术全栈、面试专栏
 * @version 1.0.0
 * @date 2023年07月02日 21:07
 * 博客地址：<a href="http://woaijava.cc/">博客地址</a>
 */
@Component
@ConfigurationProperties(prefix = "user")
public class PreConfiguration {
    private String userName;
    private Integer age;

    //set get 省略
}

Verification:

GET

http://localhost:8089/preconfiguration/index

us Usually, a type of configuration items is set as a prefix, processed uniformly, and object-oriented.

But, how to deal with multiple reads (array type)?

We can use the following method.

也是ConfigurationProperties注解

在application.properties配置文件配置项：

vip.userList[0].name=tian01
vip.userList[0].age=20
vip.userList[1].name=tian02
vip.userList[1].age=21

定义一个User类：

public class User {
    private String name;
    private Integer age;
    
    //set get toString 省略
}

配置读取类：

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

import java.util.List;

/**
 * @author tianwc  公众号：java后端技术全栈、面试专栏
 * @version 1.0.0
 * @date 2023年07月02日 21:24
 * 博客地址：<a href="http://woaijava.cc/">博客地址</a>
 */
@Component
@ConfigurationProperties(prefix = "vip")
public class UserListConfiguration {
    private List<User> userList;
    // set get 省略
}

如果我们自定义一个custom.properties配置文件，那又该如何读取呢？

PropertySource注解

在application.properties配置文件配置项：

realName=tian3

代码实现

@RestController
@RequestMapping("/propertySource")
@PropertySource("classpath:custom.properties")
public class PropertySourceController {

    @Value("${realName}")
    private String realName;
    @GetMapping("/index")
    public String test() {
        return realName;
    }
}

验证：

GET

http://localhost:8089/propertySource/index

返回参数：tian3

那么，问题又来了，我们可能会因为一个配置项需要改，或者是上线后发现配置项不对，这时候就需要重启服务了，为了避免这样重启服务，我们可以引入分布式配置中心。

分布式配置中心有很多实现方案，比如Nacos、Zookeeper、Qconf、disconf、Apache Commons Configuration、Spring Cloud Config等。

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