Configuration

The langchain4j-cdi-config module integrates with MicroProfile Config to externalize the configuration of AI components. This allows you to configure chat models, embedding models, memory providers, and other components without changing code.

Setup

<dependency>
    <groupId>dev.langchain4j.cdi.mp</groupId>
    <artifactId>langchain4j-cdi-config</artifactId>
    <version>${langchain4j-cdi.version}</version>
</dependency>

Configuration Properties

Properties follow the pattern:

langchain4j.<component>.<name>.<property>

Chat Model Configuration

langchain4j.chat-model.default.provider=openai
langchain4j.chat-model.default.api-key=${OPENAI_API_KEY}
langchain4j.chat-model.default.model-name=gpt-4o
langchain4j.chat-model.default.temperature=0.7

Plugin-Based Configuration

Components can be created entirely from configuration:

dev.langchain4j.cdi.plugin.my-model.class=dev.langchain4j.model.openai.OpenAiChatModel
dev.langchain4j.cdi.plugin.my-model.scope=jakarta.enterprise.context.ApplicationScoped
dev.langchain4j.cdi.plugin.my-model.config.apiKey=${OPENAI_API_KEY}
dev.langchain4j.cdi.plugin.my-model.config.modelName=gpt-4o

The plugin creator uses reflection to invoke the builder pattern (static builder() method + inner *Builder class).

Special Lookup Values

Configuration values support CDI bean lookups:

Value	Description
lookup:@default	Select the default CDI bean
lookup:@all	All beans of this type as a list
lookup:<name>	Named bean lookup

Expression Resolution

Annotation attribute values support two expression types:

MicroProfile Config Expressions

@RegisterAIService(chatModelName = "${ai.chat-model.name}")

Requires the langchain4j-cdi-config module.

Jakarta EL Expressions

@RegisterAIService(chatModelName = "#{configBean.chatModelName}")

Requires the langchain4j-cdi-el module and a Jakarta EL implementation (e.g., org.glassfish.expressly:expressly).

LLMConfig SPI

For programmatic configuration, implement the LLMConfigProvider SPI:

public class MyConfigProvider implements LLMConfigProvider {
    @Override
    public LLMConfig getConfig() {
        return LLMConfig.builder()
            // configure components
            .build();
    }
}