Spring Boot 有哪幾種讀取配置的方式？

Spring Boot 能夠經過 @PropertySource,@Value,@Environment, @ConfigurationProperties 來綁定變量。

Spring Boot讀取配置的幾種方式：

讀取application文件

在application.yml或者properties文件中添加：

info.address=USA
info.company=Spring
info.degree=high

一、@Value註解讀取方式

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class InfoConfig1 {

    @Value("${info.address}")
    private String address;
    
    @Value("${info.company}")
    private String company;
    
    @Value("${info.degree}")
    private String degree;

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getCompany() {
        return company;
    }

    public void setCompany(String company) {
        this.company = company;
    }

    public String getDegree() {
        return degree;
    }

    public void setDegree(String degree) {
        this.degree = degree;
    }
}

二、@ConfigurationProperties註解讀取方式

@Component
@ConfigurationProperties(prefix = "info")
public class InfoConfig2 {

    private String address;
    private String company;
    private String degree;

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getCompany() {
        return company;
    }

    public void setCompany(String company) {
        this.company = company;
    }

    public String getDegree() {
        return degree;
    }

    public void setDegree(String degree) {
        this.degree = degree;
    }
}

讀取指定文件

資源目錄下創建config/db-config.properties:

db.username=root
db.password=123456

一、@PropertySource+@Value註解讀取方式

@Component
@PropertySource(value = {"config/db-config.properties"})
public class DBConfig1 {

    @Value("${db.username}")
    private String username;
    
    @Value("${db.password}")
    private String password;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

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

注意：@PropertySource不支持yml文件讀取。

二、@PropertySource+@ConfigurationProperties註解讀取方式

@Component
@ConfigurationProperties(prefix = "db")
@PropertySource(value = {"config/db-config.properties"})
public class DBConfig2 {

    private String username;
    private String password;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

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

Environment讀取方式

以上全部加載出來的配置均可以經過Environment注入獲取到。

@Autowired
private Environment env;

//獲取參數
String getProperty(String key);

總結

從以上示例來看，Spring Boot能夠經過@PropertySource,@Value,@Environment,@ConfigurationProperties來綁定變量。