Spring Boot 有哪几种读取配置的方式？

Spring Boot 能够经过 @PropertySource,@Value,@Environment, @ConfigurationProperties 来绑定变量。

Spring Boot读取配置的几种方式：

读取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注解读取方式

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注解读取方式

@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;
    }
}

读取指定文件

资源目录下创建config/db-config.properties:

db.username=root
db.password=123456

一、@PropertySource+@Value注解读取方式

@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文件读取。

二、@PropertySource+@ConfigurationProperties注解读取方式

@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读取方式

以上全部加载出来的配置均可以经过Environment注入获取到。

@Autowired
private Environment env;

//获取参数
String getProperty(String key);

总结

从以上示例来看，Spring Boot能够经过@PropertySource,@Value,@Environment,@ConfigurationProperties来绑定变量。