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2020/9/24

Spring Boot 使用@ConfigurationProperties 綁定properties至Bean

Spring除了能使用@Value把properties配置設定值注入到成員變數中外,也可透過@ConfigurationProperties將properties檔內容綁定到Bean類的屬性。

範例環境:

  • Java 8
  • Spring Boot 2.3.2.RELEASE
  • Maven
  • Lombok

system.properites在Maven專案的src/main/resources classpath目錄,為要注入bean的properties檔。

system.properties

system.name=Demo system
system.version=1.0.0
system.url=192.168.0.111
system.port=8080

注入system.properites內容的bean,在類別名稱前加上@ConfigurationProperties,屬性prefix可設定key的前綴。

SystemProperties

package com.abc.demo.properties;

import lombok.Getter;
import lombok.Setter;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

@Getter
@Setter
@ConfigurationProperties(prefix = "system")
@Component
public class SystemProperties {

    private String name;    // system.name
    private String version; // system.version
    private String url;     // system.url
    private String port;    // system.port

}

記得在配置類設定@PropertySource指定classpath下的system.properties

DemoApplication

package com.abc.demo;

import com.abc.demo.properties.SystemProperties;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.PropertySource;

@PropertySource("classpath:system.properties")
@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {

        ApplicationContext ctx = SpringApplication.run(DemoApplication.class, args);
        SystemProperties systemProperties = ctx.getBean(SystemProperties.class);

        System.out.println(systemProperties.getName());
        System.out.println(systemProperties.getVersion());
        System.out.println(systemProperties.getUrl());
        System.out.println(systemProperties.getPort());
        
        // 菜鳥工程師肉豬
    }

}

啟動專案印出結果。

Demo system
1.0.0
192.168.0.111
8080


SystemProperties除了用一般的@Compoment註冊為bean外,可改用在配置類加上@EnableConfigurationProperties注釋來註冊指定的類,例如修改如下。

DemoApplication

package com.abc.demo;

import com.abc.demo.properties.SystemProperties;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.PropertySource;
...

@EnableConfigurationProperties(SystemProperties.class) // 註冊SystemProperties為bean
@PropertySource("classpath:system.properties")
@SpringBootApplication
public class DemoApplication {
    ...
}


@EnableConfigurationProperties指定的類不能同時使用@Compoment,否則啟動時會出現
org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'com.abc.demo.properties.SystemProperties' available: expected single matching bean but found 2: systemProperties,system-com.abc.demo.properties.SystemProperties錯誤。

SystemProperties

package com.abc.demo.properties;

import lombok.Getter;
import lombok.Setter;
import org.springframework.boot.context.properties.ConfigurationProperties;

@Getter
@Setter
@ConfigurationProperties(prefix = "system")
//@Component // <-- @EnableConfigurationProperties指定的類不能同時使用@Compoment
public class SystemProperties {

    private String name;    // system.name
    private String version; // system.version
    private String url;     // system.url
    private String port;    // system.port

}

參考github


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