This example demonstrates how to register a custom HttpMessageConverter.
A custom converter
This is just an empty extension of StringHttpMessageConverter for keeping things simple.
package com.logicbig.example;
import org.springframework.http.converter.StringHttpMessageConverter;
public class TheCustomConverter extends StringHttpMessageConverter {
}
Registering the converter
Following configuration will replace all default converters.
package com.logicbig.example;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.HttpMessageConverters;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
@Configuration
@EnableWebMvc
public class AppConfig implements WebMvcConfigurer {
@Override
public void configureMessageConverters(
HttpMessageConverters.ServerBuilder builder) {
builder.configureMessageConvertersList(
converters -> {
converters.clear();
converters.add(new TheCustomConverter());
});
}
}
Integration Test
package com.logicbig.example;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit.jupiter.SpringExtension;
import org.springframework.test.context.web.WebAppConfiguration;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;
import java.util.List;
import static org.junit.jupiter.api.Assertions.assertTrue;
@ExtendWith(SpringExtension.class)
@WebAppConfiguration
@ContextConfiguration(classes = AppConfig.class)
public class MessageConverterListTest {
@Autowired
private RequestMappingHandlerAdapter handlerAdapter;
@Test
public void messageConverterListTest() {
List<HttpMessageConverter<?>> converters =
handlerAdapter.getMessageConverters();
System.out.println("-- Converters --");
converters.stream()
.map(Object::getClass)
.map(Class::getSimpleName)
.forEach(x -> System.out.println(" -"+x));
assertTrue(!converters.isEmpty());
}
}
mvn clean test -Dtest="MessageConverterListTest" Output$ mvn clean test -Dtest="MessageConverterListTest"
[INFO] Scanning for projects...
[INFO]
[INFO] --------< com.logicbig.example:message-converters-registration >--------
[INFO] Building message-converters-registration 1.0-SNAPSHOT
[INFO] from pom.xml
[INFO] --------------------------------[ war ]---------------------------------
[INFO]
[INFO] --- clean:3.2.0:clean (default-clean) @ message-converters-registration ---
[INFO] Deleting D:\example-projects\spring-mvc\message-converters-registration\target
[INFO]
[INFO] --- resources:3.3.1:resources (default-resources) @ message-converters-registration ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory D:\example-projects\spring-mvc\message-converters-registration\src\main\resources
[INFO]
[INFO] --- compiler:3.15.0:compile (default-compile) @ message-converters-registration ---
[INFO] Recompiling the module because of changed source code.
[INFO] Compiling 3 source files with javac [debug target 25] to target\classes
[INFO]
[INFO] --- resources:3.3.1:testResources (default-testResources) @ message-converters-registration ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory D:\example-projects\spring-mvc\message-converters-registration\src\test\resources
[INFO]
[INFO] --- compiler:3.15.0:testCompile (default-testCompile) @ message-converters-registration ---
[INFO] Recompiling the module because of changed dependency.
[INFO] Compiling 2 source files with javac [debug target 25] to target\test-classes
[INFO]
[INFO] --- surefire:3.2.5:test (default-test) @ message-converters-registration ---
[INFO] Using auto detected provider org.apache.maven.surefire.junitplatform.JUnitPlatformProvider
[WARNING] file.encoding cannot be set as system property, use <argLine>-Dfile.encoding=...</argLine> instead
[INFO]
[INFO] -------------------------------------------------------
[INFO] T E S T S
[INFO] -------------------------------------------------------
[INFO] Running com.logicbig.example.MessageConverterListTest
-- Converters --
-TheCustomConverter
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 1.138 s -- in com.logicbig.example.MessageConverterListTest
[INFO]
[INFO] Results:
[INFO]
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 7.434 s
[INFO] Finished at: 2026-07-24T00:41:20+08:00
[INFO] ------------------------------------------------------------------------
Extending existing converter list
Overriding extendMessageConverters()
package com.logicbig.example;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.HttpMessageConverters;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import java.util.List;
@Configuration
@EnableWebMvc
public class AppConfig2 implements WebMvcConfigurer {
@Override
public void configureMessageConverters(
HttpMessageConverters.ServerBuilder builder) {
builder.addCustomConverter(new TheCustomConverter());
}
}
Integration test
package com.logicbig.example;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit.jupiter.SpringExtension;
import org.springframework.test.context.web.WebAppConfiguration;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;
import java.util.List;
import static org.junit.jupiter.api.Assertions.assertTrue;
@ExtendWith(SpringExtension.class)
@WebAppConfiguration
@ContextConfiguration(classes = AppConfig2.class)
public class MessageConverterListTest2 {
@Autowired
private RequestMappingHandlerAdapter handlerAdapter;
@Test
public void messageConverterListTest() {
List<HttpMessageConverter<?>> converters =
handlerAdapter.getMessageConverters();
System.out.println("-- Converters --");
converters.stream()
.map(Object::getClass)
.map(Class::getSimpleName)
.forEach(x -> System.out.println(" -"+x));
assertTrue(!converters.isEmpty());
}
}
mvn clean test -Dtest="MessageConverterListTest2" Output$ mvn clean test -Dtest="MessageConverterListTest2"
[INFO] Scanning for projects...
[WARNING]
[WARNING] Some problems were encountered while building the effective model for com.logicbig.example:message-converters-registration:war:1.0-SNAPSHOT
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-war-plugin is missing. @ line 37, column 21
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING]
[INFO]
[INFO] --------< com.logicbig.example:message-converters-registration >--------
[INFO] Building message-converters-registration 1.0-SNAPSHOT
[INFO] from pom.xml
[INFO] --------------------------------[ war ]---------------------------------
[INFO]
[INFO] --- clean:3.2.0:clean (default-clean) @ message-converters-registration ---
[INFO] Deleting D:\example-projects\spring-mvc\message-converters-registration\target
[INFO]
[INFO] --- resources:3.3.1:resources (default-resources) @ message-converters-registration ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory D:\example-projects\spring-mvc\message-converters-registration\src\main\resources
[INFO]
[INFO] --- compiler:3.5.1:compile (default-compile) @ message-converters-registration ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 3 source files to D:\example-projects\spring-mvc\message-converters-registration\target\classes
[INFO]
[INFO] --- resources:3.3.1:testResources (default-testResources) @ message-converters-registration ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory D:\example-projects\spring-mvc\message-converters-registration\src\test\resources
[INFO]
[INFO] --- compiler:3.5.1:testCompile (default-testCompile) @ message-converters-registration ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 2 source files to D:\example-projects\spring-mvc\message-converters-registration\target\test-classes
[INFO]
[INFO] --- surefire:3.2.5:test (default-test) @ message-converters-registration ---
[INFO] Using auto detected provider org.apache.maven.surefire.junit4.JUnit4Provider
[WARNING] file.encoding cannot be set as system property, use <argLine>-Dfile.encoding=...</argLine> instead
[INFO]
[INFO] -------------------------------------------------------
[INFO] T E S T S
[INFO] -------------------------------------------------------
[INFO] Running com.logicbig.example.MessageConverterListTest2
-- Converters --
-ByteArrayHttpMessageConverter
-StringHttpMessageConverter
-ResourceHttpMessageConverter
-SourceHttpMessageConverter
-AllEncompassingFormHttpMessageConverter
-Jaxb2RootElementHttpMessageConverter
-TheCustomConverter
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.701 s -- in com.logicbig.example.MessageConverterListTest2
[INFO]
[INFO] Results:
[INFO]
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 4.026 s
[INFO] Finished at: 2026-07-23T19:08:02+08:00
[INFO] ------------------------------------------------------------------------
Example ProjectDependencies and Technologies Used: - spring-webmvc 7.0.6 (Spring Web MVC)
Version Compatibility: 4.1.3.RELEASE - 7.0.6 Version compatibilities of spring-webmvc with this example: Versions in green have been tested.
- spring-test 7.0.6 (Spring TestContext Framework)
- jakarta.servlet-api 6.1.0 (Jakarta Servlet API documentation)
- junit-jupiter-engine 6.0.3 (Module "junit-jupiter-engine" of JUnit)
- JDK 25
- Maven 3.9.11
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