nacos统一配置中心第2 章：PropertySourceLocator

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李延 LV6 2021-06-18

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# 作用

我们在前面分析中知道spring-cloud是通过在父文的PropertySourceLocator对象加载配置的。

# 加载

![image](//cdn.hiboot.cn/5040bf65c87b4ba2a5dccccb82fc8559.png)

在nacos-config包中我们看到了对NacosPropertySourceLocator类的加载。

# 主要方法

我们直接看它的locateCollection方法

这个方法是使用父类的默认实现

```java

default Collection<PropertySource<?>> locateCollection(Environment environment) {
		return locateCollection(this, environment);
	}

static Collection<PropertySource<?>> locateCollection(PropertySourceLocator locator, Environment environment) {
		PropertySource<?> propertySource = locator.locate(environment);
		if (propertySource == null) {
			return Collections.emptyList();
		}
		if (CompositePropertySource.class.isInstance(propertySource)) {
			Collection<PropertySource<?>> sources = ((CompositePropertySource) propertySource).getPropertySources();
			List<PropertySource<?>> filteredSources = new ArrayList<>();
			for (PropertySource<?> p : sources) {
				if (p != null) {
					filteredSources.add(p);
				}
			}
			return filteredSources;
		}
		else {
			return Arrays.asList(propertySource);
		}
	}

```

这里我们看到又去调用了子类中的locate方法

```java
@Override
	public PropertySource<?> locate(Environment env) {
		nacosConfigProperties.setEnvironment(env);
		ConfigService configService = nacosConfigManager.getConfigService();

if (null == configService) {
			log.warn("no instance of config service found, can't load config from nacos");
			return null;
		}
		long timeout = nacosConfigProperties.getTimeout();
		nacosPropertySourceBuilder = new NacosPropertySourceBuilder(configService,
				timeout);
		String name = nacosConfigProperties.getName();

String dataIdPrefix = nacosConfigProperties.getPrefix();
		if (StringUtils.isEmpty(dataIdPrefix)) {
			dataIdPrefix = name;
		}

if (StringUtils.isEmpty(dataIdPrefix)) {
			dataIdPrefix = env.getProperty("spring.application.name");
		}

CompositePropertySource composite = new CompositePropertySource(
				NACOS_PROPERTY_SOURCE_NAME);

loadSharedConfiguration(composite);
		loadExtConfiguration(composite);
		loadApplicationConfiguration(composite, dataIdPrefix, nacosConfigProperties, env);
		return composite;
	}

```

前面都是一些对于配置的加载，主要是loadApplicationConfiguration方法

```java

private void loadApplicationConfiguration(
			CompositePropertySource compositePropertySource, String dataIdPrefix,
			NacosConfigProperties properties, Environment environment) {
		String fileExtension = properties.getFileExtension();
		String nacosGroup = properties.getGroup();
		// load directly once by default
		loadNacosDataIfPresent(compositePropertySource, dataIdPrefix, nacosGroup,
				fileExtension, true);
		// load with suffix, which have a higher priority than the default
		loadNacosDataIfPresent(compositePropertySource,
				dataIdPrefix + DOT + fileExtension, nacosGroup, fileExtension, true);
		// Loaded with profile, which have a higher priority than the suffix
		for (String profile : environment.getActiveProfiles()) {
			String dataId = dataIdPrefix + SEP1 + profile + DOT + fileExtension;
			loadNacosDataIfPresent(compositePropertySource, dataId, nacosGroup,
					fileExtension, true);
		}

}
```

其中有一个主要的方法loadNacosDataIfPresent 加载变量这里一共分为3种情况：

1. 只根据服务名称加载
2. 服务名称与文档类型拼接后加载
3. 根据启动的不提环境加载对应文件

我们具体看一下 loadNacosDataIfPresent 方法

```java
private void loadNacosDataIfPresent(final CompositePropertySource composite,
			final String dataId, final String group, String fileExtension,
			boolean isRefreshable) {
		if (null == dataId || dataId.trim().length() < 1) {
			return;
		}
		if (null == group || group.trim().length() < 1) {
			return;
		}
		NacosPropertySource propertySource = this.loadNacosPropertySource(dataId, group,
				fileExtension, isRefreshable);
		this.addFirstPropertySource(composite, propertySource, false);
	}

```

我们看到通过loadNacosPropertySource加载便利，并通过addFirstPropertySource将其添加到CompositePropertySource对象中

```java
	private NacosPropertySource loadNacosPropertySource(final String dataId,
			final String group, String fileExtension, boolean isRefreshable) {
		//刷新计数
		if (NacosContextRefresher.getRefreshCount() != 0) {
			if (!isRefreshable) {
				return NacosPropertySourceRepository.getNacosPropertySource(dataId,
						group);
			}
		}
		return nacosPropertySourceBuilder.build(dataId, group, fileExtension,
				isRefreshable);
	}

```

这里我们看到一个NacosContextRefresher.getRefreshCount。对于变量刷新的控制，这快内容我们统一放在变量刷新统一说明。

一直debug nacosPropertySourceBuilder.build代码最后会到下面内容：

```java

private String getConfigInner(String tenant, String dataId, String group, long timeoutMs) throws NacosException {
        group = null2defaultGroup(group);
        ParamUtils.checkKeyParam(dataId, group);
        ConfigResponse cr = new ConfigResponse();
        
        cr.setDataId(dataId);
        cr.setTenant(tenant);
        cr.setGroup(group);
        
        // 优先使用本地配置
        String content = LocalConfigInfoProcessor.getFailover(agent.getName(), dataId, group, tenant);
        if (content != null) {
            LOGGER.warn("[{}] [get-config] get failover ok, dataId={}, group={}, tenant={}, config={}", agent.getName(),
                    dataId, group, tenant, ContentUtils.truncateContent(content));
            cr.setContent(content);
            configFilterChainManager.doFilter(null, cr);
            content = cr.getContent();
            return content;
        }
        
        try {
            String[] ct = worker.getServerConfig(dataId, group, tenant, timeoutMs);
            cr.setContent(ct[0]);
            
            configFilterChainManager.doFilter(null, cr);
            content = cr.getContent();
            
            return content;
        } catch (NacosException ioe) {
            if (NacosException.NO_RIGHT == ioe.getErrCode()) {
                throw ioe;
            }
            LOGGER.warn("[{}] [get-config] get from server error, dataId={}, group={}, tenant={}, msg={}",
                    agent.getName(), dataId, group, tenant, ioe.toString());
        }
        
        LOGGER.warn("[{}] [get-config] get snapshot ok, dataId={}, group={}, tenant={}, config={}", agent.getName(),
                dataId, group, tenant, ContentUtils.truncateContent(content));
        content = LocalConfigInfoProcessor.getSnapshot(agent.getName(), dataId, group, tenant);
        cr.setContent(content);
        configFilterChainManager.doFilter(null, cr);
        content = cr.getContent();
        return content;
    }
```

这里我们看到主要分为两步：
1. 通过LocalConfigInfoProcessor 加载本地缓存
2. 通过worker.getServerConfig加载远程变量

## 远程

我们先看worker.getServerConfig
```java

public String[] getServerConfig(String dataId, String group, String tenant, long readTimeout)
            throws NacosException {
        String[] ct = new String[2];
        if (StringUtils.isBlank(group)) {
            group = Constants.DEFAULT_GROUP;
        }
        
        HttpRestResult<String> result = null;
        try {
            Map<String, String> params = new HashMap<String, String>(3);
            if (StringUtils.isBlank(tenant)) {
                params.put("dataId", dataId);
                params.put("group", group);
            } else {
                params.put("dataId", dataId);
                params.put("group", group);
                params.put("tenant", tenant);
            }
            result = agent.httpGet(Constants.CONFIG_CONTROLLER_PATH, null, params, agent.getEncode(), readTimeout);
        } catch (Exception ex) {
            String message = String
                    .format("[%s] [sub-server] get server config exception, dataId=%s, group=%s, tenant=%s",
                            agent.getName(), dataId, group, tenant);
            LOGGER.error(message, ex);
            throw new NacosException(NacosException.SERVER_ERROR, ex);
        }
```

这里我们看到最后也是去调用了API接口。其中接口为BASE_PATH + "/configs"

## 本地缓存LocalConfigInfoProcessor

```java

public static String getFailover(String serverName, String dataId, String group, String tenant) {
        File localPath = getFailoverFile(serverName, dataId, group, tenant);
        if (!localPath.exists() || !localPath.isFile()) {
            return null;
        }
        
        try {
            return readFile(localPath);
        } catch (IOException ioe) {
            LOGGER.error("[" + serverName + "] get failover error, " + localPath, ioe);
            return null;
        }
    }
```

代码很简单就是去读取本地的文件。我们看一下这个文件路径

```java

static {
        LOCAL_FILEROOT_PATH =
                System.getProperty("JM.LOG.PATH", System.getProperty("user.home")) + File.separator + "nacos"
                        + File.separator + "config";
        LOCAL_SNAPSHOT_PATH =
                System.getProperty("JM.SNAPSHOT.PATH", System.getProperty("user.home")) + File.separator + "nacos"
                        + File.separator + "config";
        LOGGER.info("LOCAL_SNAPSHOT_PATH:{}", LOCAL_SNAPSHOT_PATH);
    }
```

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nacos统一配置中心 第2 章：PropertySourceLocator

nacos统一配置中心第2 章：PropertySourceLocator