SpringBoot整合OSS中的设计模式----单例模式

在SpringBoot项目中使用OSS存储上传的图片，需要配置OSS设置信息。避免对象的重复创建，确保一个类只有一个实例，并提供一个全局访问点来访问该实例，于是用到了单例模式，这里复习一下单例模式。

单线程----懒汉式

@Data
@Component
@ConfigurationProperties(prefix = "aliyun.oss")
public class AliyunOssUtil {

    private static String endpoint;

    private static String accessKeyId;

    private static String accessKeySecret;

    private String bucketName;

    private static OSS ossClient = null;
    
    public static OSS getInstance(){
        if (null == ossClient){
            ossClient = new OSSClientBuilder().build(endpoint, accessKeyId, accessKeySecret);
        }
        return ossClient;
    }
}

多线程----懒汉式

@Data
@Component
@ConfigurationProperties(prefix = "aliyun.oss")
public class AliyunOssUtil {

    private static String endpoint;

    private static String accessKeyId;

    private static String accessKeySecret;

    private String bucketName;

    private static OSS ossClient = null;

    public static synchronized OSS getInstance(){
        if (null == ossClient){
            ossClient = new OSSClientBuilder().build(endpoint, accessKeyId, accessKeySecret);
        }
        return ossClient;
    }

双重检查锁----懒汉式

@Data
@Component
@ConfigurationProperties(prefix = "aliyun.oss")
public class AliyunOssUtil {

    private static String endpoint;

    private static String accessKeyId;

    private static String accessKeySecret;

    private String bucketName;

    private static OSS ossClient = null;

    public static OSS getInstance(){
        if (null == ossClient){
            synchronized (AliyunOssUtil.class){
                if (null == ossClient) {
                    ossClient = new OSSClientBuilder().build(endpoint, accessKeyId, accessKeySecret);
                }
            }
        }
        return ossClient;
    }
}

静态内部类----懒汉式（推荐）

@Data
@Component
@ConfigurationProperties(prefix = "aliyun.oss")
public class AliyunOssUtil {

    private static String endpoint;

    private static String accessKeyId;

    private static String accessKeySecret;

    private String bucketName;

    private static final class OssClientHolder {
        static final OSS ossClient = new OSSClientBuilder().build(endpoint, accessKeyId, accessKeySecret);
    }

    public static OSS getInstance(){
        return OssClientHolder.ossClient;
    }
}

饿汉式，在类初始化时已经自行实例化。

@Data
@Component
@ConfigurationProperties(prefix = "aliyun.oss")
public class AliyunOssUtil {

    private static String endpoint;

    private static String accessKeyId;

    private static String accessKeySecret;

    private String bucketName;

    private static final OSS ossClient = new OSSClientBuilder().build(endpoint, accessKeyId, accessKeySecret);

    public static OSS getInstance(){
        return ossClient;
    }
}