Mastering Spring Boot 3 & Apache Camel: Real‑World ProducerTemplate Cases

1. Introduction

Apache Camel is an open‑source integration framework based on Enterprise Integration Patterns. It supports DSLs such as Java, XML, Groovy and YAML, and can connect to many protocols (HTTP, Kafka, JMS, etc.) via a unified API.

2. Practical Cases

2.1 ProducerTemplate Overview

Similar to JdbcTemplate, ProducerTemplate sends messages to Camel routes. The two most common methods are sendBody() (one‑way, inOnly) and requestBody() (request‑reply, inOut).

2.2 Environment Setup

Add the Camel Spring Boot starter dependency:

<dependency>
  <groupId>org.apache.camel.springboot</groupId>
  <artifactId>camel-spring-boot-starter</artifactId>
  <version>4.12.0</version>
</dependency>

If the application runs without spring-boot-starter-web, enable continuous run:

camel:
  springboot:
    main-run-controller: true

2.3 Defining Routes

Extend RouteBuilder and define four routes:

@Component
public class CamelRoute extends RouteBuilder {
  @Override
  public void configure() {
    // 1. Log and transform
    from("direct:start").log("Received: ${body}").transform(simple("Hello ${body}"));
    // 2. Write to file
    from("direct:fileRoute").to("file://d:/data/temp?fileName=output.txt&fileExist=Append");
    // 3. Call a bean
    from("direct:beanRoute").bean(ProcessingBean.class, "process");
    // 4. Chat with LangChain4j
    from("direct:chat")
      .to("langchain4j-chat:test?chatModel=#openAiChatModel&chatOperation=CHAT_SINGLE_MESSAGE_WITH_PROMPT");
  }
}

ProcessingBean Definition

@Component
public class ProcessingBean {
  public String process(String input) {
    return "ProcessingBean 处理消息: " + input.toUpperCase();
  }
}

2.4 Using ProducerTemplate in a Controller

Inject ProducerTemplate and expose endpoints:

@RestController
@RequestMapping("/router")
public class RouterController {
  private final ProducerTemplate producerTemplate;
  public RouterController(ProducerTemplate producerTemplate) {
    this.producerTemplate = producerTemplate;
  }

  @GetMapping("/simple")
  public String sendSimpleMessage(String message) {
    return producerTemplate.requestBody("direct:start", message, String.class);
  }

  @GetMapping("/file")
  public String sendToFile(String message) {
    producerTemplate.sendBody("direct:fileRoute", message + "
");
    return String.format("%s 成功追加到文件output.txt中", message);
  }

  @GetMapping("/bean")
  public String sendToBean(String message) {
    return producerTemplate.requestBody("direct:beanRoute", message, String.class);
  }

  @GetMapping("/chat")
  public String chat(String message) {
    return producerTemplate.requestBodyAndHeader(
      "direct:chat", java.util.Collections.emptyMap(),
      org.apache.camel.component.langchain4j.ChatHeaders.PROMPT_TEMPLATE, message, String.class);
  }
}

Test results are shown in the following screenshots:

2.5 AI Chat Integration

Add dependencies for Camel LangChain4j and the OpenAI starter, then configure:

<dependency>
  <groupId>org.apache.camel.springboot</groupId>
  <artifactId>camel-langchain4j-chat-starter</artifactId>
  <version>4.12.0</version>
</dependency>
<dependency>
  <groupId>dev.langchain4j</groupId>
  <artifactId>langchain4j-open-ai-spring-boot-starter</artifactId>
</dependency>

langchain4j:
  open-ai:
    chat-model:
      api-key: sk-xxxooo
      model-name: qwen-turbo
      base-url: https://dashscope.aliyuncs.com/compatible-mode/v1
      temperature: 0.1

Use requestBodyAndHeader with ChatHeaders.PROMPT_TEMPLATE to send prompts, optionally with variables.

For more Camel applications, see the linked article.