SpringBoot如何动态更新yml文件？

前言

在系统运行过程中，可能由于一些配置项的简单变动需要重新打包启停项目，这对于在运行中的项目会造成数据丢失，客户操作无响应等情况发生，针对这类情况对开发框架进行升级提供yml文件实时修改更新功能

项目依赖

项目基于的是2.0.0.RELEASE版本，所以snakeyaml需要单独引入，高版本已包含在内

            org.yaml
            snakeyaml
            1.23
        

网上大多数方法是引入spring-cloud-context配置组件调用ContextRefresher的refresh方法达到同样的效果，考虑以下两点未使用

• 开发框架使用了logback日志，引入spring-cloud-context会造成日志配置读取错误
• 引入spring-cloud-context会同时引入spring-boot-starter-actuator组件，会开放一些健康检查路由及端口，需要框架安全方面进行额外控制

YML文件内容获取

读取resource文件下的文件需要使用ClassPathResource获取InputStream

public String getTotalYamlFileContent() throws Exception {
        String fileName = "application.yml";
        return getYamlFileContent(fileName);
    }
    public String getYamlFileContent(String fileName) throws Exception {
        ClassPathResource classPathResource = new ClassPathResource(fileName);
        return onvertStreamToString(classPathResource.getInputStream());
    }
    public static String convertStreamToString(InputStream inputStream) throws Exception{
       return IOUtils.toString(inputStream, "utf-8");
    }

YML文件内容更新

我们获取到yml文件内容后可视化显示到前台进行展示修改，将修改后的内容通过yaml.load方法转换成Map结构，再使用yaml.dumpAsMap转换为流写入到文件

public void updateTotalYamlFileContent(String content) throws Exception {
        String fileName = "application.yml";
        updateYamlFileContent(fileName, content);
    }
    public void updateYamlFileContent(String fileName, String content) throws Exception {
        Yaml template = new Yaml();
        Map yamlMap = template.load(content);

        ClassPathResource classPathResource = new ClassPathResource(fileName);

        Yaml yaml = new Yaml();
        //字符输出
        FileWriter fileWriter = new FileWriter(classPathResource.getFile());
        //用yaml方法把map结构格式化为yaml文件结构
        fileWriter.write(yaml.dumpAsMap(yamlMap));
        //刷新
        fileWriter.flush();
        //关闭流
        fileWriter.close();
    }

YML属性刷新

yml属性在程序中读取使用一般有三种

• 使用Value注解

@Value("${system.systemName}")
    private String systemName;

• 通过enviroment注入读取

@Autowired
    private Environment environment;
    
    environment.getProperty("system.systemName")

• 使用ConfigurationProperties注解读取

@Component
@ConfigurationProperties(prefix = "system")
public class SystemConfig {
    private String systemName;
}

Property刷新

我们通过environment.getProperty方法读取的配置集合实际是存储在PropertySources中的，我们只需要把键值对全部取出存储在propertyMap中，将更新后的yml文件内容转换成相同格式的ymlMap，两个Map进行合并，调用PropertySources的replace方法进行整体替换即可

但是yaml.load后的ymlMap和PropertySources取出的propertyMap两者数据解构是不同的，需要进行手动转换

propertyMap集合就是单纯的key，value键值对，key是properties形式的名称，例如system.systemName=>xxxxx集团管理系统

ymlMap集合是key，LinkedHashMap的嵌套层次结构，例如system=>(systemName=>xxxxx集团管理系统)

• 转换方法如下

public HashMap convertYmlMapToPropertyMap(Map yamlMap) {
        HashMap propertyMap = new HashMap();
        for (String key : yamlMap.keySet()) {
            String keyName = key;
            Object value = yamlMap.get(key);
            if (value != null && value.getClass() == LinkedHashMap.class) {
                convertYmlMapToPropertyMapSub(keyName, ((LinkedHashMap) value), propertyMap);
            } else {
                propertyMap.put(keyName, value);
            }
        }
        return propertyMap;
    }

    private void convertYmlMapToPropertyMapSub(String keyName, LinkedHashMap submMap, Map propertyMap) {
        for (String key : submMap.keySet()) {
            String newKey = keyName + "." + key;
            Object value = submMap.get(key);
            if (value != null && value.getClass() == LinkedHashMap.class) {
                convertYmlMapToPropertyMapSub(newKey, ((LinkedHashMap) value), propertyMap);
            } else {
                propertyMap.put(newKey, value);
            }
        }
    }

• 刷新方法如下

String name = "applicationConfig: [classpath:/" + fileName + "]";
        MapPropertySource propertySource = (MapPropertySource) environment.getPropertySources().get(name);
        Map source = propertySource.getSource();
        Map map = new HashMap<>(source.size());
        map.putAll(source);

        Map propertyMap = convertYmlMapToPropertyMap(yamlMap);

        for (String key : propertyMap.keySet()) {
            Object value = propertyMap.get(key);
            map.put(key, value);
        }
        environment.getPropertySources().replace(name, new MapPropertySource(name, map));

注解刷新

不论是Value注解还是ConfigurationProperties注解，实际都是通过注入Bean对象的属性方法使用的，我们先自定注解RefreshValue来修饰属性所在Bean的class

通过实现
InstantiationAwareBeanPostProcessorAdapter接口在系统启动时过滤筛选对应的Bean存储下来，在更新yml文件时通过spring的event通知更新对应

bean的属性即可

• 注册事件使用EventListener注解

@EventListener
    public void updateConfig(ConfigUpdateEvent configUpdateEvent) {
        if(mapper.containsKey(configUpdateEvent.key)){
            List fieldPairList = mapper.get(configUpdateEvent.key);
            if(fieldPairList.size()>0){
                for (FieldPair fieldPair:fieldPairList) {
                    fieldPair.updateValue(environment);
                }
            }
        }
    }

• 通知触发事件使用ApplicationContext的publishEvent方法

@Autowired
    private ApplicationContext applicationContext;
    
    for (String key : propertyMap.keySet()) {
       applicationContext.publishEvent(new YamlConfigRefreshPostProcessor.ConfigUpdateEvent(this, key));
    }

YamlConfigRefreshPostProcessor的完整代码如下

@Component
public class YamlConfigRefreshPostProcessor extends InstantiationAwareBeanPostProcessorAdapter implements EnvironmentAware {
    private Map> mapper = new HashMap<>();
    private Environment environment;

    @Override
    public boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
        processMetaValue(bean);
        return super.postProcessAfterInstantiation(bean, beanName);
    }

    @Override
    public void setEnvironment(Environment environment) {
        this.environment = environment;
    }

    private void processMetaValue(Object bean) {
        Class clz = bean.getClass();
        if (!clz.isAnnotationPresent(RefreshValue.class)) {
            return;
        }

        if (clz.isAnnotationPresent(ConfigurationProperties.class)) {
            //@ConfigurationProperties注解
            ConfigurationProperties config = (ConfigurationProperties) clz.getAnnotation(ConfigurationProperties.class);
            for (Field field : clz.getDeclaredFields()) {
                String key = config.prefix() + "." + field.getName();
                if(mapper.containsKey(key)){
                    mapper.get(key).add(new FieldPair(bean, field, key));
                }else{
                    List fieldPairList = new ArrayList<>();
                    fieldPairList.add(new FieldPair(bean, field, key));
                    mapper.put(key, fieldPairList);
                }
            }
        } else {
            //@Valuez注解
            try {
                for (Field field : clz.getDeclaredFields()) {
                    if (field.isAnnotationPresent(Value.class)) {
                        Value val = field.getAnnotation(Value.class);
                        String key = val.value().replace("${", "").replace("}", "");
                        if(mapper.containsKey(key)){
                            mapper.get(key).add(new FieldPair(bean, field, key));
                        }else{
                            List fieldPairList = new ArrayList<>();
                            fieldPairList.add(new FieldPair(bean, field, key));
                            mapper.put(key, fieldPairList);
                        }
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
                System.exit(-1);
            }
        }
    }

    public static class FieldPair {
        private static PropertyPlaceholderHelper propertyPlaceholderHelper = new PropertyPlaceholderHelper("${", "}",
                ":", true);
        private Object bean;
        private Field field;
        private String value;

        public FieldPair(Object bean, Field field, String value) {
            this.bean = bean;
            this.field = field;
            this.value = value;
        }

        public void updateValue(Environment environment) {
            boolean access = field.isAccessible();
            if (!access) {
                field.setAccessible(true);
            }
            try {
                if (field.getType() == String.class) {
                    String updateVal = environment.getProperty(value);
                    field.set(bean, updateVal);
                }
                else if (field.getType() == Integer.class) {
                    Integer updateVal = environment.getProperty(value,Integer.class);
                    field.set(bean, updateVal);
                }
                else if (field.getType() == int.class) {
                    int updateVal = environment.getProperty(value,int.class);
                    field.set(bean, updateVal);
                }
                else if (field.getType() == Boolean.class) {
                    Boolean updateVal = environment.getProperty(value,Boolean.class);
                    field.set(bean, updateVal);
                }
                else if (field.getType() == boolean.class) {
                    boolean updateVal = environment.getProperty(value,boolean.class);
                    field.set(bean, updateVal);
                }
                else {
                    String updateVal = environment.getProperty(value);
                    field.set(bean, JSONObject.parseObject(updateVal, field.getType()));
                }
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
            field.setAccessible(access);
        }

        public Object getBean() {
            return bean;
        }

        public void setBean(Object bean) {
            this.bean = bean;
        }

        public Field getField() {
            return field;
        }

        public void setField(Field field) {
            this.field = field;
        }

        public String getValue() {
            return value;
        }

        public void setValue(String value) {
            this.value = value;
        }
    }

    public static class ConfigUpdateEvent extends ApplicationEvent {
        String key;

        public ConfigUpdateEvent(Object source, String key) {
            super(source);
            this.key = key;
        }
    }

    @EventListener
    public void updateConfig(ConfigUpdateEvent configUpdateEvent) {
        if(mapper.containsKey(configUpdateEvent.key)){
            List fieldPairList = mapper.get(configUpdateEvent.key);
            if(fieldPairList.size()>0){
                for (FieldPair fieldPair:fieldPairList) {
                    fieldPair.updateValue(environment);
                }
            }
        }
    }
}