Apache Camel：使用 predicateBuilder 复合条件并从 when() 函数访问它们

Question

我正在尝试使用 PredicateBuilder 组合条件并将其保存到 header 以从 when() 函数访问谓词。一开始我将 body 设置为 Hello World。 body 也不为空或不等于 AUTHENTICATE failed 但我进入 when 块并且正在记录 process_no_mail_or_failed 。我不明白我做错了什么。我如何在 Apache Camel 中复合谓词并使用它们在 when() 函数中？万一我必须在某个步骤检查 body 。所以顺路做了。

非常感谢您的帮助！

Apache Camel 路由：

import org.apache.camel.Exchange;
import org.apache.camel.Message;
import org.apache.camel.Predicate;
import org.apache.camel.Processor;
import org.apache.camel.builder.PredicateBuilder;
import org.apache.camel.builder.RouteBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

@Component
public class TestRoute  extends RouteBuilder {
    
    static final Logger LOGGER = LoggerFactory.getLogger(EmailPollingRoute.class);
    static final String AUTHENTICATE_FAILED = "AUTHENTICATE failed.";
    
    @Override
    public void configure() throws Exception {

        from("quartz://emailTimer?cron=0/30+*+*+*+*+?+*")
        .log("TestRoute - Before calling transform")
        .process(new Processor() {
            @Override
            public void process(Exchange exchange) throws Exception {
                Message message = exchange.getIn();
                message.setBody("Hello World");
                String body = message.getBody(String.class);
                LOGGER.info("body: \n" + body);
                
                Predicate p1 = body().isNull();
                Predicate p2 = body().isEqualTo(AUTHENTICATE_FAILED);
                Predicate predicate_result12 = PredicateBuilder.or(p1, p2);
                message.setHeader("process_no_mail_or_failed", predicate_result12);
                
            }   
        })
        .choice()
        .when(header("process_no_mail_or_failed").convertTo(Predicate.class)) 
        //.when(simple("${body} == null || ${body} == 'AUTHENTICATE failed.'")) //This works for me. I am getting into the otherwise block
           .log("when: ${body}")
           
        .otherwise()
           .log("otherwise: ${body}");
    
    }
}

Answer 1

Predicates 有 matches 方法，你可以用它来评估谓词

如果您想获得 Predicate 的结果，您可以使用 matches-method 来评估谓词。

from("direct:example")
    .routeId("example")
    .process(exchange -> {

        Predicate bodyNotNullOrEmpty = PredicateBuilder.and(
            body().isNotEqualTo(null), 
            body().isNotEqualTo("")
        );
        Boolean result = bodyNotNullOrEmpty.matches(exchange);
        exchange.getMessage().setHeader("bodyNotNullOrEmpty", result);
    })
    .choice().when(header("bodyNotNullOrEmpty"))
        .log("body: ${body}")
    .otherwise()
        .log("Body is null or empty")
    .end()
    .to("mock:result");

您也可以只从 Predicate 构建器导入静态方法并在选择中使用它们，而不必存储结果以进行交换属性。

这个从 Predicate 构建器导入静态方法的技巧很容易被忽略，因为它只在文档的 negate predicates section 中提到过。

import static org.apache.camel.builder.PredicateBuilder.not;
import static org.apache.camel.builder.PredicateBuilder.and;

...

from("direct:example")
    .routeId("example")
    .choice()
        .when(and(body().isNotNull(), body().isNotEqualTo("")))
            .log("body: ${body}")
        .otherwise()
            .log("Body is null or empty")
    .end()
    .to("mock:result");

Apache Camel：使用 predicateBuilder 复合条件并从 when() 函数访问它们

Apache Camel: compound conditions by using the predicateBuilder and access them from the when() function

java

apache-camel