通过get方法的方式获取配置项信息

这种写法比其他的方法好的一点是，当你需要修改参数名或者参数值的时候，只需要改一个地方就可以了，其他地方根本不用动，面向接口编程。

eureka-server.properties

archaius.dynamicPropertyFactory.Default_getInstanceId=inistanceid
archaius.dynamicPropertyFactory.DEFAULT_GETAPPNAME=getname
archaius.dynamicPropertyFactory.DEFAULT_APPGROUPNAME

package com.liwei.leshop.eureka.config;

/**
 * 常量类
 */
public class Content {
    public static final String URL_CONFIG_NAME = "archaius.dynamicPropertyFactory.URL_CONFIG";
    public static final String DEFAULT_GETINSTANCEID = "archaius.dynamicPropertyFactory.Default_getInstanceId";
    public static final String DEFAULT_GETAPPNAME = "archaius.dynamicPropertyFactory.DEFAULT_GETAPPNAME";
    public static final String SYS_CONFIG_NAME = "archaius.dynamicPropertyFactory.SYS_CONFIG";
    public static final String ENV_CONFIG_NAME = "archaius.dynamicPropertyFactory.ENV_CONFIG";
    public static final String DEFAULT_APPGROUPNAME = "archaius.dynamicPropertyFactory.DEFAULT_APPGROUPNAME";
}

/**
 * server编码
 */
public interface EurekaServiceConfig {

    String getInstanceId();

    String getAppname();

    String getAppGroupName();

}

package com.liwei.leshop.eureka.config;

import java.io.IOException;
import java.io.InputStream;
import java.util.Optional;
import java.util.Properties;

public class PropertiesInstanceConfig implements EurekaServiceConfig {
    public static void main(String[] args) {
        PropertiesInstanceConfig config = PropertiesInstanceConfig.getPropertiesInstanceConfig();
        System.out.println( config.getAppGroupName());
    }
    public static Properties properties = new Properties();

    static volatile PropertiesInstanceConfig instance = null;

    public static PropertiesInstanceConfig getPropertiesInstanceConfig() {
        if (instance == null) {
            synchronized (PropertiesInstanceConfig.class) {
                if (instance == null) {
                    instance = new PropertiesInstanceConfig();
                }
            }
        }
        return instance;
    }

    private PropertiesInstanceConfig() {
        InputStream in = PropertiesInstanceConfig.class.getClassLoader().getResourceAsStream("eureka-server.properties");
        try {
            properties.load(in);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public String getInstanceId() {
        return String.valueOf(Optional.ofNullable(properties.get(Content.DEFAULT_GETINSTANCEID)).orElse("Default_getInstanceId"));
    }

    @Override
    public String getAppname() {
        return String.valueOf(Optional.ofNullable( properties.get(Content.DEFAULT_GETAPPNAME)).orElse("Default_getAppname"));

    }

    @Override
    public String getAppGroupName() {
        return String.valueOf(Optional.ofNullable(properties.get(Content.DEFAULT_GETAPPNAME)).orElse("deflut"));
    }
}