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SpringBoot RestTemplate 相关问题和解决思路

1.   采用spring resttemplate方案，适用场景
2.   被调服务端需要Bearer token验证的方案设计
3.   被调服务端需要SSL验证的架构设计
4.   如何实现请求失败重试，利用spring retry
5.   如何快速进行模型转换，避免adapter，setter and getter.
6.   如何对接口和方法进行缓存， 利用spring cache和hibernate 二级缓存技术
7.   如何实现 x-trace功能，追踪整个请求链条。

• 后端需要向其他服务发起Rest请求调用，拿到结果并返回

使用Spring Rest Tempalte， https://spring.io/guides/gs/consuming-rest/

RestTemplate restTemplate = new RestTemplate();

• 被调用服务启用token机制，需要在每个请求里注入 Authorization: Beaer TOKEN****

为了使得获取和注入token机制与业务功能代码解耦，需要在resttemplate注入自定义interceptor https://www.tutorialspoint.com/spring_boot/spring_boot_interceptor.htm

interceptor file:

public class DemoInterceptor implements ClientHttpRequestInterceptor {
    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, 
    ClientHttpRequestExecution execution){
        //get token here.
        String tokenValue = String.format("%s %s", "Authorization", "XXXXXXXXXXX");
        request.getHeaders().add("Authorization", tokenValue);
    }
}

resttemplate add interceptor

DemoInterceptor ris = new DemoInterceptor();
restTemplate.setInterceptors(Arrays.asList({ris});

• 使用https调用服务

把cert文件生成jks证书, 生成方式参考：

openssl pkcs12 -export -in server.crt  -inkey server.key -out server.pkcs12
keytool -importkeystore -srckeystore server.pkcs12 -destkeystore server-keystore.jks -srcstoretype pkcs12

新建ssl request builder

public class SslRequestFactoryBuilder {   
    private static Logger logger = LoggerFactory.getLogger(SslRequestFactoryBuilder.class);
    public ClientHttpRequestFactory build(SslOption sslOption) {
        HttpClientBuilder httpClientBuilder = HttpClients.custom();
        if (sslOption != null && sslOption.getEnable() != null && sslOption.getEnable()) {
            logger.info("ssl connection is being enabled");
            SSLContext sslContext = getSslContext(sslOption);
            httpClientBuilder.setSSLContext(sslContext);
        } else {
            logger.info("ssl connection not active, use http instead");
        }
        CloseableHttpClient client = httpClientBuilder.build();
        ClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(client);
        ClientHttpRequestFactory bufferRequestFactory = new BufferingClientHttpRequestFactory(requestFactory);
        return bufferRequestFactory;
    }
    private SSLContext getSslContext(SslOption sslOption) {
        SSLContext sslContext;
        try {
            sslContext = SSLContextBuilder
                    .create()
                    .loadKeyMaterial(ResourceUtils.getFile(sslOption.getKeyStore()),
                            sslOption.getKeyStorePassword().toCharArray(),
                            sslOption.getKeyPass().toCharArray())
                    .loadTrustMaterial(ResourceUtils.getFile(sslOption.getTrustStore()),
                            sslOption.getTrustStorePassword().toCharArray())
                    .build();
        } catch (Exception e) {
            logger.error("ssl restTemplate initialize failed!");
            throw new RuntimeException("ssl restTemplate initialize failed!", e);
        }
        return sslContext;
    }
}

resttemplate add interceptor

ClientHttpRequestFactory requestFactory = builder.buildPool(sslOption)
restTemplate.setRequestFactory(requestFactory);

• 请求失败重试

添加spring retry依赖 https://www.baeldung.com/spring-retry, enable retrying

@Retryable(
        value = {RetryException.class},
        maxAttemptsExpression = "2",
        backoff = @Backoff(5000))
public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
    ClientHttpResponse response = execution.execute(request, body);
    // if error, throw exception
    throw new RetryException("retry");
    return response;
}

• 请求数据结果与领域模型转换

添加 Dozer 转换框架, http://dozer.sourceforge.net/

compile('net.sf.dozer:dozer:5.4.0')

定义class A 和 B， A为数据DTO, B为领域模型

class A{

    @mapping("at1")
    private String attr1;
    
    @mapping("at2")
    private String attr2;
    private String attr3;
    ...
}

class B{
    private String at1;
    private String at2;
    ...
}

源数据转为目标数据

Mapper mapper = new DozerBeanMapper();
B b = mapper.map(a, B.class)

• 处于性能考虑，需要对请求结果进行缓存

采用 Spring Cache + ehcache方案,https://www.baeldung.com/spring-boot-ehcache

添加项目依赖,spring boot enable cache

compile('javax.cache:cache-api')
compile('org.ehcache:ehcache:3.6.1')
compile('org.springframework.boot:spring-boot-starter-cache')

新增cache配置

@Configuration
public class ProfileCacheConfig implements JCacheManagerCustomizer {
    private static Logger logger = LoggerFactory.getLogger(ProfileCacheConfig.class);
    @Autowired
    private ProfileProperties profileProperties;
    @Override
    public void customize(CacheManager cacheManager) {
        CacheProperty cacheProperty = profileProperties.getCache();
        cacheManager.createCache("CACHE_NAME", new MutableConfiguration<>()
                .setExpiryPolicyFactory(ModifiedExpiryPolicy.factoryOf(new Duration(TimeUnit.MINUTES, cacheProperty.getProfileExpireMinutes())))
                .setStoreByValue(false));
    }
}

 

在方法上面添加cacheable注解，启用缓存

@Cacheable(value = "CACHE_NAME", key = "#param")
public void method(string param){
    ******
}

• 给每个请求添加x-trace链路跟踪

采用MDC方案，将生成的x-trace-Id注入到request,response的header里面

拦截每个前端发送给每个后端的请求, 继承HandlerInterceptorAdapter，生成x-trace-Id, 注入到 MDC context里面

public class XTraceInterceptor extends HandlerInterceptorAdapter {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        String xTraceId = generateTraceId();
        MDC.put("x-trace-Id", xTraceId);
        response.setHeader("x-trace-Id", xTraceId);
        return true;
    }

    private String generateTraceId() {
        String randomId = UUID.randomUUID().toString();
        String xTraceId = String.format("%s-%s", "demo", randomId);
        return xTraceId;
    }
}

拓展WebMvcConfigurationSupport，将XTraceInterceptor注入

public class AppConfig extends WebMvcConfigurationSupport {
    @Override
    protected void addInterceptors(InterceptorRegistry registry) {
        XTraceInterceptor xtrace = new XTraceInterceptor();
        registry.addInterceptor(loggerInterceptor);
        super.addInterceptors(registry);
    }
}

restTemplate调用服务的时候,新建interceptor,在取出来注入到request header当中

public class LoggingRequestInterceptor implements ClientHttpRequestInterceptor {
    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, 
    ClientHttpRequestExecution execution) throws IOException {
        String xTraceId = MDC.get(LoggerAttributeKeys.X_TRACE_ID);
        if (xTraceId != null) {
            request.getHeaders().add(LoggerAttributeKeys.X_TRACE_ID, xTraceId);
        }
        ClientHttpResponse response = execution.execute(request, body);
        return response;
    }
}