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# Configuration
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The Quarkus Undertow extension provides both runtime and build-time configuration options for controlling servlet behavior, performance settings, and server configuration.
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## Configuration Import
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Configuration is handled through Quarkus configuration system:
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```java
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import io.quarkus.undertow.runtime.ServletRuntimeConfig;
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import io.quarkus.undertow.deployment.ServletConfig;
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import io.smallrye.config.ConfigMapping;
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```
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## Runtime Configuration
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Runtime configuration properties affect the behavior during application execution and can be modified at runtime.
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### ServletRuntimeConfig
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Runtime configuration interface for servlet settings.
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```java { .api }
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@ConfigMapping(prefix = "quarkus.servlet")
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public interface ServletRuntimeConfig {
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    /**
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     * Buffer size for servlet operations
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     * Configuration property: quarkus.servlet.buffer-size
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     */
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    Optional<MemorySize> bufferSize();
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    /**
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     * Whether to use direct buffers
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     * Configuration property: quarkus.servlet.direct-buffers
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     */
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    Optional<Boolean> directBuffers();
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    /**
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     * Maximum number of HTTP request parameters
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     * Configuration property: quarkus.servlet.max-parameters
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     * Default value: 1000
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     */
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    @WithDefault("1000")
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    int maxParameters();
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}
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```
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### Runtime Configuration Properties
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| Property | Type | Default | Description |
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|----------|------|---------|-------------|
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| `quarkus.servlet.buffer-size` | `MemorySize` | - | Buffer size for servlet operations (e.g., "8K", "1M") |
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| `quarkus.servlet.direct-buffers` | `boolean` | - | Whether to use direct buffers for improved performance |
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| `quarkus.servlet.max-parameters` | `int` | `1000` | Maximum number of HTTP request parameters |
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#### Usage Example
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```properties
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# application.properties
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quarkus.servlet.buffer-size=16K
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quarkus.servlet.direct-buffers=true
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quarkus.servlet.max-parameters=2000
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```
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## Build-time Configuration
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Build-time configuration properties are resolved during application build and cannot be changed at runtime.
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### ServletConfig
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Build-time configuration interface for servlet settings.
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```java { .api }
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@ConfigMapping(prefix = "quarkus.servlet")
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public interface ServletConfig {
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    /**
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     * Context path for servlet content
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     * Configuration property: quarkus.servlet.context-path
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     */
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    Optional<String> contextPath();
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    /**
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     * Default charset for requests and responses
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     * Configuration property: quarkus.servlet.default-charset
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     * Default value: UTF-8
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     */
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    @WithDefault("UTF-8")
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    String defaultCharset();
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}
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```
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### ServletConfig.ContextPathConverter
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Converter for processing context path values.
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```java { .api }
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public static class ContextPathConverter implements Converter<String> {
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    /**
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     * Convert and validate context path value
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     */
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    public String convert(String value) throws IllegalArgumentException;
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}
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```
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### Build-time Configuration Properties
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| Property | Type | Default | Description |
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|----------|------|---------|-------------|
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| `quarkus.servlet.context-path` | `String` | - | Context path for servlet content (e.g., "/api", "/webapp") |
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| `quarkus.servlet.default-charset` | `String` | `UTF-8` | Default charset for HTTP requests and responses |
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#### Usage Example
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```properties
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# application.properties
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quarkus.servlet.context-path=/api
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quarkus.servlet.default-charset=UTF-8
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```
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## Advanced Configuration
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### Performance Tuning
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For high-throughput applications, consider these configuration optimizations:
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```properties
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# Enable direct buffers for better performance
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quarkus.servlet.direct-buffers=true
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# Increase buffer size for large requests
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quarkus.servlet.buffer-size=32K
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# Adjust max parameters for complex forms
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quarkus.servlet.max-parameters=5000
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```
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### Development Configuration
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For development environments, you might want different settings:
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```properties
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# Development profile (application-dev.properties)
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quarkus.servlet.context-path=/dev
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quarkus.servlet.max-parameters=500
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```
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### Production Configuration
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For production deployments:
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```properties
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# Production profile (application-prod.properties)
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quarkus.servlet.context-path=/
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quarkus.servlet.buffer-size=64K
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quarkus.servlet.direct-buffers=true
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quarkus.servlet.max-parameters=10000
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```
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## Configuration Injection
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You can inject configuration into your application components:
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```java
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@ApplicationScoped
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public class ServletConfigService {
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    @Inject
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    ServletRuntimeConfig runtimeConfig;
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    public void logConfiguration() {
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        System.out.println("Max parameters: " + runtimeConfig.maxParameters());
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        runtimeConfig.bufferSize().ifPresent(size -> 
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            System.out.println("Buffer size: " + size));
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        runtimeConfig.directBuffers().ifPresent(direct -> 
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            System.out.println("Direct buffers: " + direct));
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    }
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}
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```
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## Environment-specific Configuration
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Use Quarkus profiles to configure different environments:
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```properties
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# Base configuration
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quarkus.servlet.default-charset=UTF-8
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# Development profile
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%dev.quarkus.servlet.context-path=/dev
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%dev.quarkus.servlet.max-parameters=100
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# Test profile  
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%test.quarkus.servlet.context-path=/test
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%test.quarkus.servlet.max-parameters=50
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# Production profile
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%prod.quarkus.servlet.context-path=/
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%prod.quarkus.servlet.buffer-size=64K
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%prod.quarkus.servlet.direct-buffers=true
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```
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## Types
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```java { .api }
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// Configuration annotations
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import io.smallrye.config.ConfigMapping;
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import io.smallrye.config.WithDefault;
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import io.smallrye.config.Converter;
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// Memory size type
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import io.quarkus.runtime.configuration.MemorySize;
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// Standard Java types
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import java.util.Optional;
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// CDI injection
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import jakarta.inject.Inject;
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import jakarta.enterprise.context.ApplicationScoped;
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```