spring-boot 自定义 endpoint，让运行时的 java 应用不再是黑盒

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你的 java 应用在运行时对你来说是黑盒吗？你可以查看到 springboot 运行时的各种信息吗？

Spring Boot Actuator

springboot 提供了用于健康检测的 endpoint，提供了查看系统信息、内存、环境等。

1. 添加依赖

   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-actuator</artifactId>
   </dependency>

2. 访问链接

应用启动后访问 http://localhost:8080/health 查看应用启动状态。
端口号可以通过配置文件 management.port=9527 变更

常用 endpoint

1. http://localhost:8080/env 环境变量
2. http://localhost:8080/info 应用信息
3. http://localhost:8080/metrics 内存等应用基本指标
4. http://localhost:8080/dump 线程栈
5. http://localhost:8080/configprops 配置项

3. 开启全部 endpoint & 关闭验权

部分请求会返回 401， 这是因为 endpoint 未开启，或者开启了登录验权，可以通过配置文件进行配置

management.security.enabled=false
endpoints.enabled=true

自定义 endpoint

一、实现 Endpoint 接口

    public interface Endpoint<T> {
    	String getId();
    
    	boolean isEnabled();
    
    	boolean isSensitive();
    
    	T invoke();
    }

1. getId()， 指定了 endpoint 访问 url
2. isEnabled()， 表示是否启用
3. isSensitive()， 表示是否验权
4. invoke()， 页面返回值

实现类通过 @Bean 的形式注入后，再次启动应用，即可通过 url 访问，并返回 invoke 返回值。

    public class CustomEndpoint implements Endpoint {
    
        @Override
        public String getId() {
            return "custom";
        }
    
        @Override
        public boolean isEnabled() {
            return true;
        }
    
        @Override
        public boolean isSensitive() {
            return false;
        }
    
        @Override
        public Object invoke() {
            return "hello endpoint";
        }
    }

    @SpringBootApplication
    public class EndpointApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(EndpointApplication.class, args);
        }
    
    
        @Bean
        public CustomEndpoint customEndpoint() {
            return new CustomEndpoint();
        }
    }

访问 http://localhost:8080/custom 可以看到 invoke 返回的内容。

但是这样，每个 endpoint 都需要单独注入，且没有层级、通配符，不方便管理，为满足需求，尝试做了如下改造

二、继承 EndpointMvcAdapter

2.1 自定义 EndpointAction 接口

用于定制 endpoint 处理行为，可以理解为 invoke 方法的具体实施者，名称用来管理访问路径

    public interface EndpointAction extends Serializable {
        Object execute();
    
        String getName();
    }

2.2 EndpointAction 的多种实现

需要实现的功能，如：读取配置文件、查看内存信息

    @Component
    public class PropertiesAction implements EndpointAction {
    
        @Override
        public Object execute() {
            try {
                return PropertiesLoaderUtils.loadAllProperties("application.properties");
            } catch (IOException e) {
                return "read application fail! error: " + e.getMessage();
            }
        }
    
        @Override
        public String getName() {
            return "properties";
        }
    }

    @Component
    public class VMAction implements EndpointAction {
    
        private static final VMAction INSTANCE = new VMAction();
    
        private String version;
        private String startTime;
        private String initHeap;
        private String maxHeap;
        private Set<String> arguments;
    
        @Override
        public Object execute() {
            INSTANCE.version = System.getProperty("java.runtime.version");
            INSTANCE.startTime = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(ManagementFactory.getRuntimeMXBean().getStartTime());
            INSTANCE.initHeap = String.valueOf(ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getInit() / 1024 / 1024).concat("MB");
            INSTANCE.maxHeap = String.valueOf(ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getMax() / 1024 / 1024).concat("MB");
            INSTANCE.arguments = new HashSet<>(ManagementFactory.getRuntimeMXBean().getInputArguments());
            return INSTANCE;
        }
    
        @Override
        public String getName() {
            return "vm";
        }
    
        public String getVersion() {
            return version;
        }
    
        public String getStartTime() {
            return startTime;
        }
    
        public String getInitHeap() {
            return initHeap;
        }
    
        public String getMaxHeap() {
            return maxHeap;
        }
    
        public Set<String> getArguments() {
            return arguments;
        }
    }

    @Component
    public class DefaultAction implements EndpointAction {
    
    
        private static final DefaultAction INSTANCE = new DefaultAction();
    
        public static DefaultAction getInstance() {
            return INSTANCE;
        }
    
        @Override
        public Object execute() {
            return "try /help for action list";
        }
    
        @Override
        public String getName() {
            return "default";
        }
    
    }

2.3 继承 EndpointMvcAdapter

1. 注入 action map，根据 name 获取 bean 实现
2. 通过 url mapping 匹配 action

    public class CustomEndpointAdapter extends EndpointMvcAdapter {
    
    
        private Map<String, EndpointAction> endpointActionMap = new HashMap<>();
    
        @Autowired
        public void setEndpointActionMap(List<EndpointAction> endpointActionList) {
            endpointActionList.forEach(endpointAction -> endpointActionMap.put(endpointAction.getName(), endpointAction));
        }
    
        public CustomEndpointAdapter() {
            super(new CustomEndpoint());
        }
    
        @RequestMapping(value = "/{name:.*}",
                method = RequestMethod.GET, produces = {
                ActuatorMediaTypes.APPLICATION_ACTUATOR_V1_JSON_VALUE,
                MediaType.APPLICATION_JSON_VALUE}
        )
        @ResponseBody
        @HypermediaDisabled
        public Object dispatcher(@PathVariable String name) {
            if ("help".equalsIgnoreCase(name)) {
                return endpointActionMap.keySet().stream().map(key -> getName() + "/" + key).collect(toSet());
            } else {
                return endpointActionMap.getOrDefault(name, DefaultAction.getInstance()).execute();
            }
        }
    
    }

2.4 定制 endpoint 作为入口

    public class CustomEndpoint implements Endpoint {
    
        @Override
        public String getId() {
            return "custom";
        }
    
        @Override
        public boolean isEnabled() {
            return true;
        }
    
        @Override
        public boolean isSensitive() {
            return false;
        }
    
        @Override
        public Object invoke() {
            return DefaultAction.getInstance().execute();
        }
    }

2.5 启动时注入

    @SpringBootApplication
    public class EndpointApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(EndpointApplication.class, args);
        }
    
    
        @Bean
        @ConditionalOnMissingBean
        @ConditionalOnClass(CustomEndpoint.class)
        public CustomEndpointAdapter customEndpointAdapter() {
            return new CustomEndpointAdapter();
        }
    }

测试

揪心的测试环节，启动 webEnvironment 环境，通过 TestRestTemplate 访问 endpoint 的 mapping，比对返回值即可

    @RunWith(SpringRunner.class)
    @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
    public class PropertiesActionTest {
    
        private TestRestTemplate restTemplate;
    
        @Value("${management.port}")
        private String managementPort;
    
        @Before
        public void setupMockMvc() {
            restTemplate = new TestRestTemplate();
        }
    
        @Test
        public void test_properties_action() throws Exception {
            String path = "http://localhost:" + managementPort + "/custom/properties";
            Map<String, String> result = restTemplate.getForObject(path, HashMap.class);
            assertEquals(result.get("management.port"), managementPort);
        }
    
        @Test
        public void test_help() throws Exception {
            String path = "http://localhost:" + managementPort + "/custom/help";
            Set<String> result = restTemplate.getForObject(path, Set.class);
            assertTrue(result.contains("custom/properties"));
        }
    
        @Test
        public void test_rand() throws Exception {
            String path = "http://localhost:" + managementPort + "/custom/" + new Random().nextInt();
            String result = restTemplate.getForObject(path, String.class);
            assertEquals("try /help for action list", result);
    
        }
    
    }