- 现象：收到消息会打印告警消息:：Could not convert incoming message with content-type [null]
- 解决：
RabbitMQ已经实现了Jackson的消息转换（Jackson2JsonMessageConverter），由于考虑到效率，如下使用Gson实现消息转换。
如下消息的转换类的接口MessageConverter，Jackson2JsonMessageConverter的父类AbstractJsonMessageConverter针对json转换的基类。
我们实现Gson2JsonMessageConverter转换类也继承AbstractJsonMessageConverter。
引入Gson的pom
1. <dependency>
2. <groupId>com.google.code.gson</groupId>
3. <artifactId>gson</artifactId>
4. <version>2.3</version>
5. </dependency>转换类实现如下：
1. package cn.slimsmart.rabbitmq.demo.spring.tag;
2.
3. import java.io.IOException;
4. import java.io.UnsupportedEncodingException;
5.
6. import org.apache.commons.logging.Log;
7. import org.apache.commons.logging.LogFactory;
8. import org.springframework.amqp.core.Message;
9. import org.springframework.amqp.core.MessageProperties;
10. import org.springframework.amqp.support.converter.AbstractJsonMessageConverter;
11. import org.springframework.amqp.support.converter.ClassMapper;
12. import org.springframework.amqp.support.converter.DefaultClassMapper;
13. import org.springframework.amqp.support.converter.MessageConversionException;
14.
15. import com.google.gson.Gson;
16.
17. public class Gson2JsonMessageConverter extends AbstractJsonMessageConverter {
18.
19. private static Log log = LogFactory.getLog(Gson2JsonMessageConverter.class);
20.
21. private static ClassMapper classMapper = new DefaultClassMapper();
22.
23. private static Gson gson = new Gson();
24.
25. public Gson2JsonMessageConverter() {
26. super();
27. }
28.
29. @Override
30. protected Message createMessage(Object object,
31. MessageProperties messageProperties) {
32. byte[] bytes = null;
33. try {
34. String jsonString = gson.toJson(object);
35. bytes = jsonString.getBytes(getDefaultCharset());
36. }
37. catch (IOException e) {
38. throw new MessageConversionException(
39. "Failed to convert Message content", e);
40. }
41. messageProperties.setContentType(MessageProperties.CONTENT_TYPE_JSON);
42. messageProperties.setContentEncoding(getDefaultCharset());
43. if (bytes != null) {
44. messageProperties.setContentLength(bytes.length);
45. }
46. classMapper.fromClass(object.getClass(),messageProperties);
47. return new Message(bytes, messageProperties);
48. }
49.
50. @Override
51. public Object fromMessage(Message message)
52. throws MessageConversionException {
53. Object content = null;
54. MessageProperties properties = message.getMessageProperties();
55. if (properties != null) {
56. String contentType = properties.getContentType();
57. if (contentType != null && contentType.contains("json")) {
58. String encoding = properties.getContentEncoding();
59. if (encoding == null) {
60. encoding = getDefaultCharset();
61. }
62. try {
63. Class<?> targetClass = getClassMapper().toClass(
64. message.getMessageProperties());
65. content = convertBytesToObject(message.getBody(),
66. encoding, targetClass);
67. }
68. catch (IOException e) {
69. throw new MessageConversionException(
70. "Failed to convert Message content", e);
71. }
72. }
73. else {
74. log.warn("Could not convert incoming message with content-type ["
75. + contentType + "]");
76. }
77. }
78. if (content == null) {
79. content = message.getBody();
80. }
81. return content;
82. }
83.
84. private Object convertBytesToObject(byte[] body, String encoding,
85. Class<?> clazz) throws UnsupportedEncodingException {
86. String contentAsString = new String(body, encoding);
87. return gson.fromJson(contentAsString, clazz);
88. }
89. }
