spring-projects/spring-framework · error · IntrospectionException

Read method returns void

Error message

Read method returns void: {readMethod}

What it means

Thrown as java.beans.IntrospectionException by PropertyDescriptorUtils.findPropertyType when the supplied read method's return type is void. A JavaBeans getter must return a value; a void return makes the property type unresolvable.

Solutions

1. Change the getter to return the property type instead of void.
2. Rename the void method so it is not picked up as a getter (no getXxx/isXxx prefix).
3. Regenerate the class with corrected getter signatures.

Example fix

// before
public void getName() { return this.name; } // void return

// after
public String getName() { return this.name; }

if (readMethod != null && readMethod.getReturnType() == void.class) {
    throw new IllegalArgumentException("getter returns void: " + readMethod);
}

static boolean getterReturnsValue(Method m) {
    return m != null && m.getParameterCount() == 0 && m.getReturnType() != void.class;
}

When it happens

Trigger: findPropertyType(readMethod, writeMethod) is called and readMethod.getReturnType() == void.class. Means a void method was registered as a read method.

Common situations: A method named getXxx or isXxx that returns void (a typo, or a side-effecting 'is' method), a code generator that emitted getters incorrectly, or accidental registration of a non-getter void method as a property read method.

Related errors

• Bad indexed read method arg count
• Bad indexed write method arg count
• Bad read method arg count
• Bad write method arg count
• Indexed read method returns void

AI-assisted analysis of spring-projects/spring-framework@69bf83ad71 (2026-08-09). Data as JSON: /api/errors/4cda32fbd9cafb2d. Report an issue: GitHub.

Appendix: source

Thrown at spring-beans/src/main/java/org/springframework/beans/PropertyDescriptorUtils.java:159

		target.setBound(source.isBound());
		target.setConstrained(source.isConstrained());
	}

	/**
	 * See {@link java.beans.PropertyDescriptor#findPropertyType}.
	 */
	public static @Nullable Class<?> findPropertyType(@Nullable Method readMethod, @Nullable Method writeMethod)
			throws IntrospectionException {

		Class<?> propertyType = null;

		if (readMethod != null) {
			if (readMethod.getParameterCount() != 0) {
				throw new IntrospectionException("Bad read method arg count: " + readMethod);
			}
			propertyType = readMethod.getReturnType();
			if (propertyType == void.class) {
				throw new IntrospectionException("Read method returns void: " + readMethod);
			}
		}

		if (writeMethod != null) {
			Class<?>[] params = writeMethod.getParameterTypes();
			if (params.length != 1) {
				throw new IntrospectionException("Bad write method arg count: " + writeMethod);
			}
			if (propertyType != null) {
				if (propertyType.isAssignableFrom(params[0])) {
					// Write method's property type potentially more specific
					propertyType = params[0];
				}
				else if (params[0].isAssignableFrom(propertyType)) {
					// Proceed with read method's property type
				}
				else {
					throw new IntrospectionException(

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