RabbitMQ 使用 Policies-HTTP API 绑定和解绑 DLX

需求：

exchange 和 queue 都能重复声明不会影响已有数据，但是 DLX 只能在 queue 第一次创建的时候一起定义，否则运行时就需要通过 WEB UI 或者 rabbitmqctl set_policy 命令行指令来添加 DLX。如果对已经存在的 queue 使用 java API 的方式添加 DLX 绑定则会报错。而我在写demo时定义了默认的 exchange 和 queue，所以希望默认的 dlx 也能通过 java API 方式重复声明。

解决方案：

去官网找了一些 HTTP API 资料，但官网只给出 SET_POLICY 方式，相应的 HTTP API 没有给出具体示例。于是根据已有资料中一些其他的 HTTP API 的规则、WEB UI 中 Policies 接口的存在，还有 SET_POLISY DLX 的规律，猜测 DLX policy HTTP API 的调用方式，最后比较简单地试出了 DLX HTTP API 的调用方式。

代码会跟随 RabbitMQ 的某个小demo不久后会正式分享到 github，现在就直接贴代码吧。

Policies HTTP 设置 DLX 代码：

PS：DELETE 方法中 pattern 为 ""（空字符串）就可以了。这里没有完全优化。

 1 private static final String DEFAULT_DLX_URL = "http://192.168.33.50:15672/api/policies/%2f/DLX"
 2
 3 public static void declareDlxForDefaultQueueViaHttpClient(boolean bind) {
 4         HttpEntityEnclosingRequestBase request;
 5         if (bind) {
 6             request = new HttpPut(DEFAULT_DLX_URL);
 7         } else {
 8             request = new HttpDeleteWithEntity(DEFAULT_DLX_URL);
 9         }
10         CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
11         Credentials credentials = new UsernamePasswordCredentials(DEFAULT_USERNAME, DEFAULT_USER_PWD);
12         // 这里可以用 AuthScope.ANY 替代。表示任何 URL domain 都使用同一个 AUTH
13         credentialsProvider.setCredentials(new AuthScope(DEFAULT_HOST, DEFAULT_MANAGEMENT_PORT), credentials);
14         // BasicAuth 验证由 HttpClient API 来处理
15         CloseableHttpClient httpClient = HttpClientBuilder.create().setDefaultCredentialsProvider(credentialsProvider).build();
16         JSONObject dlxJson = new JSONObject();
17         dlxJson.put("pattern", "origin\\..*");
18         JSONObject definition = new JSONObject();
19         definition.put("dead-letter-exchange", "origin.dlx");
20         dlxJson.put("definition", definition);
21         dlxJson.put("apply-to", "queues");
22         StringEntity entity = new StringEntity(dlxJson.toString(), ContentType.APPLICATION_JSON);
23         // 有些方法不能带请求体，所以请求体不能放到 HttpClient API 里
24         request.setEntity(entity);
25         try {
26             CloseableHttpResponse httpResponse = httpClient.execute(request);
27             int statusCode = httpResponse.getStatusLine().getStatusCode();
28             HttpEntity responseEntity = httpResponse.getEntity();
29             String responseBody = responseEntity == null ? "empty response body" : EntityUtils.toString(responseEntity);
30             log.info("IN declare DLX for DEFAULT QUEUE：request method=" + request.getMethod()
31                     + ", statusCode=" + statusCode + ", responseBody=" + responseBody);
32         } catch (IOException e) {
33             e.printStackTrace();
34         }
35     }

模拟 HttpPut 构造 HttpDeleteWithEntity 代码：

 1 public class HttpDeleteWithEntity extends HttpEntityEnclosingRequestBase {
 2
 3     public final static String METHOD_NAME = "DELETE";
 4
 5     public HttpDeleteWithEntity() {
 6         super();
 7     }
 8
 9     public HttpDeleteWithEntity(final URI uri) {
10         super();
11         setURI(uri);
12     }
13
14     /**
15      * @throws IllegalArgumentException if the uri is invalid.
16      */
17     public HttpDeleteWithEntity(final String uri) {
18         super();
19         setURI(URI.create(uri));
20     }
21
22     @Override
23     public String getMethod() {
24         return METHOD_NAME;
25     }
26 }

pom.xml 代码：

 1 <dependencies>
 2         <!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->
 3         <dependency>
 4             <groupId>org.apache.httpcomponents</groupId>
 5             <artifactId>httpclient</artifactId>
 6             <version>4.5.10</version>
 7         </dependency>
 8
 9         <dependency>
10             <groupId>com.alibaba</groupId>
11             <artifactId>fastjson</artifactId>
12             <version>1.2.62</version>
13         </dependency>
14
15         <dependency>
16             <groupId>junit</groupId>
17             <artifactId>junit</artifactId>
18             <version>4.12</version>
19             <scope>test</scope>
20         </dependency>
21
22         <dependency>
23             <groupId>com.rabbitmq</groupId>
24             <artifactId>amqp-client</artifactId>
25             <version>5.4.3</version>
26             <scope>compile</scope>
27         </dependency>
28
29         <dependency>
30             <groupId>org.projectlombok</groupId>
31             <artifactId>lombok</artifactId>
32             <version>1.18.10</version>
33             <scope>provided</scope>
34         </dependency>
35
36         <!--logback 日志框架，只需要引入这个-->
37         <dependency>
38             <groupId>ch.qos.logback</groupId>
39             <artifactId>logback-classic</artifactId>
40             <version>1.2.3</version>
41         </dependency>
42     </dependencies>

maven dependencies