Reference
Pro Spring Integration - https://www.amazon.com/Pro-Spring-Integration-Experts-Voice-ebook-dp-B005PZ29OA/dp/B005PZ29OA/ref=mt_kindle?_encoding=UTF8&me=&qid=
前篇: https://www.isaacnote.com/2018/10/spring-integration-channels.html
下篇: https://www.isaacnote.com/2018/11/spring-integration-integrate-with-tomcat.html
下篇: https://www.isaacnote.com/2018/11/spring-integration-integrate-with-tomcat.html
Transformer 用來轉換收進來的訊息
Example 把 Map 或 String 改為 TextMessage. Mapper 掛上 @Transformer 就是註冊 Transformer, 根據 parameter type 可以自動判斷哪個 transformer method 要被呼叫
// Mapper
@Component
public class Mapper {
@Transformer
public TextMessage map(Map<String, String> message) {
System.out.println("transform from " + message + " to TextMessage");
return new TextMessage(message.get("text"));
}
@Transformer
public TextMessage map(String message) {
System.out.println("transform from string to TextMessage");
return new TextMessage(message);
}
}
// TextMessage
public class TextMessage {
private final String text;
public TextMessage(String text) {
this.text = text;
}
@Override
public String toString() {
return text;
}
}
// TransformerMain.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:int="http://www.springframework.org/schema/integration"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/integration
http://www.springframework.org/schema/integration/spring-integration-5.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:component-scan base-package="examples.transformer"/>
<int:transformer input-channel="input"
output-channel="output"
ref="mapper"/>
<int:channel id="input"/>
<int:channel id="output">
<int:queue capacity="10"/>
</int:channel>
</beans>
// TransformerMain.java
public class TransformerMain {
public static void main(String[] params) {
ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:TransformerMain.xml");
MessageChannel input = ctx.getBean("input", MessageChannel.class);
PollableChannel output = ctx.getBean("output", PollableChannel.class);
Map<String,String> message = new HashMap<>();
message.put("text", "here");
input.send(MessageBuilder.withPayload(message).build());
System.out.println(output.receive().getPayload());
input.send(MessageBuilder.withPayload("fromString").build());
System.out.println(output.receive().getPayload());
}
}
Object-to-string transformer
Example 不用設定 mapper 就會呼叫 toString 轉換
// ObjectToStringTransformer.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:int="http://www.springframework.org/schema/integration"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/integration
http://www.springframework.org/schema/integration/spring-integration-5.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:component-scan base-package="examples.transformer"/>
<int:object-to-string-transformer input-channel="input" output-channel="output" />
<int:channel id="input"/>
<int:channel id="output">
<int:queue capacity="10"/>
</int:channel>
</beans>
public class ObjectToStringTransformerMain {
public static void main(String[] params) {
ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:ObjectToStringTransformerMain.xml");
MessageChannel input = ctx.getBean("input", MessageChannel.class);
PollableChannel output = ctx.getBean("output", PollableChannel.class);
Map<String,String> message = new HashMap<>();
message.put("text", "here");
input.send(MessageBuilder.withPayload(message).build());
System.out.println(output.receive().getPayload());
input.send(MessageBuilder.withPayload("fromString").build());
System.out.println(output.receive().getPayload());
}
}
Payload-serializer-transformer 對 payload 直接做 serialize/deserialize
Example localId in TextMessage 是 transient, 所以不會被 serialize/deserialize
// XML
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:int="http://www.springframework.org/schema/integration"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/integration
http://www.springframework.org/schema/integration/spring-integration-5.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:component-scan base-package="examples.transformer"/>
<int:payload-serializing-transformer input-channel="input" output-channel="byte-array" />
<int:payload-deserializing-transformer input-channel="byte-array" output-channel="output" />
<int:channel id="byte-array" />
<int:channel id="input"/>
<int:channel id="output">
<int:queue capacity="10"/>
</int:channel>
</beans>
public class TextMessage implements Serializable {
private final String text;
private final transient String localId;
public TextMessage(String text) {
this(text, UUID.randomUUID().toString());
}
public TextMessage(String text, String localId) {
this.text = text;
this.localId = localId;
}
@Override
public String toString() {
return localId + ":" + text;
}
}
public class PayloadSerializingTransformerMain {
public static void main(String[] params) {
ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:PayloadSerializingTransformerMain.xml");
MessageChannel input = ctx.getBean("input", MessageChannel.class);
PollableChannel output = ctx.getBean("output", PollableChannel.class);
TextMessage message = new TextMessage("testa", "1");
input.send(MessageBuilder.withPayload(message).build());
System.out.println(output.receive().getPayload()); // localId will become null
}
}
Map-to-object transformer 替 payload 做 marshal/unmarshal to map
Example 這裡要注意的是 訊息必須有空的建構子與 setter/getter, 不然會失敗
// XML
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:int="http://www.springframework.org/schema/integration"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/integration
http://www.springframework.org/schema/integration/spring-integration-5.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:component-scan base-package="examples.transformer"/>
<int:object-to-map-transformer input-channel="input" output-channel="map" />
<int:map-to-object-transformer input-channel="map" output-channel="output" type="examples.transformer.TextMessageEmptyConstructor" />
<int:channel id="map" />
<int:channel id="input"/>
<int:channel id="output">
<int:queue capacity="10"/>
</int:channel>
</beans>
// Payload class
public class TextMessageEmptyConstructor {
private String text;
public TextMessageEmptyConstructor() {}
public TextMessageEmptyConstructor(String text) {
this.text = text;
}
public void setText(String text) {
this.text = text;
}
public String getText() {
return text;
}
@Override
public String toString() {
return text;
}
}
// Transformer
public class MapToObjectTransformerMain {
public static void main(String[] params) {
ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:MapToObjectTransformerMain.xml");
MessageChannel input = ctx.getBean("input", MessageChannel.class);
PollableChannel output = ctx.getBean("output", PollableChannel.class);
TextMessageEmptyConstructor message = new TextMessageEmptyConstructor("testa");
input.send(MessageBuilder.withPayload(message).build());
System.out.println(output.receive().getPayload()); // localId will become null
}
}
Object-to-json transformer payload 會轉成 json 再轉回 payload 物件
Example
// XML
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:int="http://www.springframework.org/schema/integration"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/integration
http://www.springframework.org/schema/integration/spring-integration-5.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:component-scan base-package="examples.transformer"/>
<int:object-to-json-transformer input-channel="input" output-channel="json" />
<int:json-to-object-transformer input-channel="json" output-channel="output" type="examples.transformer.TextMessageEmptyConstructor" />
<int:channel id="json" />
<int:channel id="input"/>
<int:channel id="output">
<int:queue capacity="10"/>
</int:channel>
</beans>
// transformer
public class ObjectToJsonTransformerMain {
public static void main(String[] params) {
ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:ObjectToJsonTransformerMain.xml");
MessageChannel input = ctx.getBean("input", MessageChannel.class);
PollableChannel output = ctx.getBean("output", PollableChannel.class);
TextMessageEmptyConstructor message = new TextMessageEmptyConstructor("test-object-to-json");
input.send(MessageBuilder.withPayload(message).build());
System.out.println(output.receive().getPayload());
}
}
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