自定義MessageConverter--消息轉換器

咱們在進行發送消息的時候，正常狀況下消息體爲二進制的數據方式進行傳輸，若是但願內部幫咱們進行轉換，或者指定自定義的轉換器，就須要用到MessageConverter

• 自定義經常使用轉換器：MessageConverter，通常來說都須要實現這個接口
• 重寫下面兩個方法： toMessage:java對象轉換爲Message fromMessage:Message對象轉換爲java對象
• Json轉換器：Jackson2JsonMessageConverter:能夠進行Java對象的轉換功能
• DefaultJackson2JavaTypeMapper映射器：能夠進行java對象的映射關係
• 自定義二進制轉換器：好比圖片類型、PDF、PPT、流媒體

在pom.xml文件中加入依賴：

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>2.10.0</version>
    </dependency>
    
    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.10.0</version>
    </dependency>

1.完成將byte數組轉換成String字符串

上節的適配器不變，在適配器中添加一個轉換器TextMessageConverter，

//1.適配器方式：默認是有本身的方法的名字的：handleMessage
        MessageListenerAdapter adapter = new MessageListenerAdapter(new MessageDelegate()); //本身指定一個默認的方法名
        adapter.setDefaultListenerMethod("consumeMessage"); //也能夠加一個轉換器：從字節數組轉換爲String
        adapter.setMessageConverter(new TextMessageConverter()); container.setMessageListener(adapter);

TextMessageConverter代碼：

package com.dwz.spring.converter; import org.springframework.amqp.core.Message; import org.springframework.amqp.core.MessageProperties; import org.springframework.amqp.support.converter.MessageConversionException; import org.springframework.amqp.support.converter.MessageConverter; public class TextMessageConverter implements MessageConverter { //將其它對象轉換成Message
 @Override public Message toMessage(Object object, MessageProperties messageProperties) throws MessageConversionException { return new Message(object.toString().getBytes(), messageProperties); } //將Message對象轉換成String
 @Override public Object fromMessage(Message message) throws MessageConversionException { String contentType = message.getMessageProperties().getContentType(); if(null != contentType && contentType.contains("text")) { System.err.println("contentType：--String--" + contentType); return new String(message.getBody()); } return message.getBody(); } }

此時咱們適配器自定義的委託對象MessageDelegate的consumeMessage()接收的參數類型要與 fromMessage()返回的類型一致

MessageDelegate類以下：

public class MessageDelegate {
    public void consumeMessage(String messageBody) { System.err.println("consumeMessage默認方法，消息內容：String--" + messageBody); }
}

測試代碼：

 @Test public void testMessage02() { //建立消息
        MessageProperties messageProperties = new MessageProperties(); messageProperties.setContentType("text/plain"); Message message = new Message("spring consumeMessage消息".getBytes(), messageProperties); rabbitTemplate.send("topic001", "spring.abc", message); rabbitTemplate.convertAndSend("topic001", "spring.amqp", "hello object message send!"); rabbitTemplate.convertAndSend("topic002", "rabbit.amqp", "hello object message send!"); }

2. 支持json格式的轉換器

添加Order和Packaged這兩個類

Order類：

package com.dwz.spring.entity; import java.io.Serializable; public class Order implements Serializable{ private static final long serialVersionUID = 1L; private String id; private String name; private String content; public Order() { super(); // TODO Auto-generated constructor stub
 } public Order(String id, String name, String content) { super(); this.id = id; this.name = name; this.content = content; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getContent() { return content; } public void setContent(String content) { this.content = content; } }

Packaged類：

package com.dwz.spring.entity; import java.io.Serializable; public class Packaged implements Serializable{ /** * */
    private static final long serialVersionUID = 1L; private String id; private String name; private String description; public Packaged() { super(); // TODO Auto-generated constructor stub
 } public Packaged(String id, String name, String description) { super(); this.id = id; this.name = name; this.description = description; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getDescription() { return description; } public void setDescription(String description) { this.description = description; } }

設置適配器中setMessageConverter(jackson2JsonMessageConverter)轉換器參數

MessageListenerAdapter adapter = new MessageListenerAdapter(new MessageDelegate()); adapter.setDefaultListenerMethod("consumeMessage"); Jackson2JsonMessageConverter jackson2JsonMessageConverter = new Jackson2JsonMessageConverter(); adapter.setMessageConverter(jackson2JsonMessageConverter); container.setMessageListener(adapter);

MessageDelegate類的consumeMessage()的入參修改成Map<String, Object>以下：

public void consumeMessage(Map<String, Object> messageBody) { System.err.println("consumeMessage的map方法，消息內容：" + messageBody); }

測試代碼：

/** * 支持json格式的轉換器 * @throws JsonProcessingException */ @Test public void testSendJsonMessage() throws JsonProcessingException { Order order = new Order(); order.setId("001"); order.setName("消息訂單"); order.setContent("描述信息"); ObjectMapper mapper = new ObjectMapper(); String json = mapper.writeValueAsString(order); System.err.println("order 4 json:" + json); MessageProperties messageProperties = new MessageProperties(); //這裏必定要修改contentType爲application/json
        messageProperties.setContentType("application/json"); Message message = new Message(json.getBytes(), messageProperties); rabbitTemplate.send("topic001", "spring.order", message); }

 3.支持java對象轉換

更改適配器部分代碼，完成Jackson2JsonMessageConverter轉換器的DefaultJackson2JavaTypeMapper設置

//1.2 DefaultJackson2JavaTypeMapper 和 Jackson2JsonMessageConverter 支持java對象轉換
        MessageListenerAdapter adapter = new MessageListenerAdapter(new MessageDelegate()); adapter.setDefaultListenerMethod("consumeMessage"); Jackson2JsonMessageConverter jackson2JsonMessageConverter = new Jackson2JsonMessageConverter(); DefaultJackson2JavaTypeMapper javaTypeMapper = new DefaultJackson2JavaTypeMapper(); //若是使用RabbitMQ默認的轉換方式，並不會涉及到本章遇到的信任package問題，若是想自定義消息轉換而且使用DefaultClassMapper做爲映射， //確定會出現信任package的問題，因此若是須要自定義轉換的小夥伴，記住要設置trustedPackages。
        javaTypeMapper.addTrustedPackages("com.dwz.spring.entity"); jackson2JsonMessageConverter.setJavaTypeMapper(javaTypeMapper); adapter.setMessageConverter(jackson2JsonMessageConverter); container.setMessageListener(adapter);

MessageDelegate類的consumeMessage()的入參修改成Order對象以下：

public void consumeMessage(Order order) { System.err.println("order對象，消息內容, id：" + order.getId() +", name:" + order.getName() +", content:" + order.getContent()); }

測試代碼：

/** * json與java對象之間的轉換 * @throws JsonProcessingException */ @Test public void testSendJavaMessage() throws JsonProcessingException { Order order = new Order(); order.setId("001"); order.setName("消息訂單"); order.setContent("描述信息"); ObjectMapper mapper = new ObjectMapper(); String json = mapper.writeValueAsString(order); System.err.println("order 4 json:" + json); MessageProperties messageProperties = new MessageProperties(); //這裏必定要修改contentType爲application/json
        messageProperties.setContentType("application/json"); messageProperties.getHeaders().put("__TypeId__", "com.dwz.spring.entity.Order"); Message message = new Message(json.getBytes(), messageProperties); rabbitTemplate.send("topic001", "spring.order", message); }

4.支持java對象多映射轉換

更改適配器部分代碼，加入多個typeid和對象的映射

//1.3 DefaultJackson2JavaTypeMapper 和 Jackson2JsonMessageConverter 支持java對象多映射轉換
        MessageListenerAdapter adapter = new MessageListenerAdapter(new MessageDelegate()); adapter.setDefaultListenerMethod("consumeMessage"); Jackson2JsonMessageConverter jackson2JsonMessageConverter = new Jackson2JsonMessageConverter(); DefaultJackson2JavaTypeMapper javaTypeMapper = new DefaultJackson2JavaTypeMapper(); Map<String, Class<?>> idClassMapping = new HashMap<String, Class<?>>(); idClassMapping.put("order", Order.class); idClassMapping.put("packaged", Packaged.class); javaTypeMapper.setIdClassMapping(idClassMapping); jackson2JsonMessageConverter.setJavaTypeMapper(javaTypeMapper); adapter.setMessageConverter(jackson2JsonMessageConverter); container.setMessageListener(adapter);

MessageDelegate類的consumeMessage()添加入參爲Order和Packaged對象的兩個重載方法以下：

public void consumeMessage(Order order) { System.err.println("order對象，消息內容, id：" + order.getId() +", name:" + order.getName() +", content:" + order.getContent()); } public void consumeMessage(Packaged pack) { System.err.println("Packaged對象，消息內容, id：" + pack.getId() +", name:" + pack.getName() +", description:" + pack.getDescription()); }

測試代碼：

要在Headers中添加

messageProperties2.getHeaders().put("__TypeId__", "packaged");

 @Test public void testSendMappingMessage() throws JsonProcessingException { Order order = new Order(); order.setId("001"); order.setName("訂單消息"); order.setContent("訂單描述信息"); ObjectMapper mapper = new ObjectMapper(); String json1 = mapper.writeValueAsString(order); System.err.println("order 4 json:" + json1); MessageProperties messageProperties = new MessageProperties(); //這裏必定要修改contentType爲application/json
        messageProperties.setContentType("application/json"); messageProperties.getHeaders().put("__TypeId__", "order"); Message message = new Message(json1.getBytes(), messageProperties); rabbitTemplate.send("topic001", "spring.order", message); Packaged packaged = new Packaged(); packaged.setId("002"); packaged.setName("包裹消息"); packaged.setDescription("包裹描述信息"); String json2 = mapper.writeValueAsString(packaged); System.err.println("packaged 4 json:" + json2); MessageProperties messageProperties2 = new MessageProperties(); //這裏必定要修改contentType爲application/json
        messageProperties2.setContentType("application/json"); messageProperties2.getHeaders().put("__TypeId__", "packaged"); Message message2 = new Message(json2.getBytes(), messageProperties2); rabbitTemplate.send("topic001", "spring.packaged", message2); }

5.全局轉換器：convert

更改適配器部分代碼，加入全局轉換器

//1.4 全局轉換器：convert
        MessageListenerAdapter adapter = new MessageListenerAdapter(new MessageDelegate()); adapter.setDefaultListenerMethod("consumeMessage"); //全局轉換器
        ContentTypeDelegatingMessageConverter convert = new ContentTypeDelegatingMessageConverter(); TextMessageConverter textConvert = new TextMessageConverter(); convert.addDelegate("text", textConvert); convert.addDelegate("html/text", textConvert); convert.addDelegate("xml/text", textConvert); convert.addDelegate("text/plain", textConvert); Jackson2JsonMessageConverter jsonConverter = new Jackson2JsonMessageConverter(); convert.addDelegate("json", jsonConverter); convert.addDelegate("application/json", jsonConverter); ImageMessageConverter imageConverter = new ImageMessageConverter(); convert.addDelegate("image/png", imageConverter); convert.addDelegate("image", imageConverter); PDFMessageConverter pdfConverter = new PDFMessageConverter(); convert.addDelegate("application/pdf", pdfConverter); adapter.setMessageConverter(convert); container.setMessageListener(adapter);

MessageDelegate類的consumeMessage()添加方法

public void consumeMessage(File file) { System.err.println("文件對象，消息內容, " + file.getName()); }

添加自定義轉換器ImageMessageConverter和PDFMessageConverter

package com.dwz.spring.converter; import java.io.ByteArrayInputStream; import java.io.File; import java.io.IOException; import java.nio.file.Files; import java.nio.file.Paths; import java.nio.file.StandardCopyOption; import java.util.UUID; import org.springframework.amqp.core.Message; import org.springframework.amqp.core.MessageProperties; import org.springframework.amqp.support.converter.MessageConversionException; import org.springframework.amqp.support.converter.MessageConverter; import org.springframework.util.FileCopyUtils; public class ImageMessageConverter implements MessageConverter { @Override public Message toMessage(Object object, MessageProperties messageProperties) throws MessageConversionException { throw new MessageConversionException(" convert error! "); } @Override public Object fromMessage(Message message) throws MessageConversionException { System.err.println("---------------Image MessageConverter-------------------"); Object _extName = message.getMessageProperties().getHeaders().get("extName"); String extName = _extName == null ? "png" : _extName.toString(); byte[] body = message.getBody(); String fileName = UUID.randomUUID().toString(); String path = "D:\\dwz_temp\\" + fileName + "." + extName; File f = new File(path); System.out.println(path); try { Files.copy(new ByteArrayInputStream(body), Paths.get(path), StandardCopyOption.REPLACE_EXISTING); // FileCopyUtils.copy(body, f);
        } catch (IOException e) { e.printStackTrace(); } return f; } }

package com.dwz.spring.converter; import java.io.ByteArrayInputStream; import java.io.File; import java.io.IOException; import java.nio.file.Files; import java.util.UUID; import org.springframework.amqp.core.Message; import org.springframework.amqp.core.MessageProperties; import org.springframework.amqp.support.converter.MessageConversionException; import org.springframework.amqp.support.converter.MessageConverter; public class PDFMessageConverter implements MessageConverter { @Override public Message toMessage(Object object, MessageProperties messageProperties) throws MessageConversionException { throw new MessageConversionException(" convert error! "); } @Override public Object fromMessage(Message message) throws MessageConversionException { System.err.println("---------------PDF MessageConverter-------------------"); byte[] body = message.getBody(); String fileName = UUID.randomUUID().toString(); String path = "D:/dwz_temp/" + fileName + ".pdf"; File f = new File(path); try { Files.copy(new ByteArrayInputStream(body), f.toPath()); } catch (IOException e) { e.printStackTrace(); } return f; } }

測試代碼：

圖片轉換測試

 @Test public void testSendImgMessage1() throws IOException { byte[] body = Files.readAllBytes(Paths.get("C:/Users/Administrator/Pictures/Saved Pictures/img02/dwz.png")); MessageProperties messageProperties = new MessageProperties(); messageProperties.setContentType("image/png"); messageProperties.getHeaders().put("extName", "png"); Message message = new Message(body, messageProperties); rabbitTemplate.send("", "image_queue", message); }

pdf文件轉換測試

 @Test public void testSendPDFMessage2() throws IOException { byte[] body = Files.readAllBytes(Paths.get("F:\\dwz\\my\\2019全新Java學習路線圖.pdf")); MessageProperties messageProperties = new MessageProperties(); messageProperties.setContentType("application/pdf"); Message message = new Message(body, messageProperties); rabbitTemplate.send("", "pdf_queue", message); }