spring-projects/spring-framework · error · IllegalArgumentException

Specify either targetClass or targetObject, not both

Error message

Specify either targetClass or targetObject, not both

What it means

Thrown as an IllegalArgumentException by FieldRetrievingFactoryBean.afterPropertiesSet when both targetClass and targetObject are set. The factory bean needs exactly one of them to know where to look up the static field; providing both is contradictory, so initialization refuses to proceed rather than guessing.

Solutions

  1. Provide exactly one of targetClass (for a static field on a class) or targetObject (for an instance field), not both.
  2. If you want a static field, keep targetClass + targetField and drop targetObject.
  3. If you want an instance field, keep targetObject + targetField and drop targetClass.
  4. Alternatively, use staticField alone ('pkg.Cls.FIELD') and let the factory bean parse class+field from it.
  5. Add a sanity check in test config to assert !(targetClass!=null && targetObject!=null) before initialization.

Example fix

<!-- before: both targetClass and targetObject set -->
<bean id='f' class='o.s.b.f.config.FieldRetrievingFactoryBean'>
  <property name='targetClass' value='com.acme.Const'/>
  <property name='targetObject' ref='someBean'/>
  <property name='targetField' value='MAX'/>
</bean>

<!-- after: static field, targetObject removed -->
<bean id='f' class='o.s.b.f.config.FieldRetrievingFactoryBean'>
  <property name='targetClass' value='com.acme.Const'/>
  <property name='targetField' value='MAX'/>
</bean>
Defensive patterns

Strategy: validation

Validate before calling

FieldRetrievingFactoryBean fb = new FieldRetrievingFactoryBean();
if (fb.getTargetClass() != null && fb.getTargetObject() != null) {
    throw new IllegalArgumentException("Set only one of targetClass/targetObject");
}

Type guard

boolean validTarget = (targetClass != null) ^ (targetObject != null);

Prevention

When it happens

Trigger: Configuring FieldRetrievingFactoryBean with both setTargetClass(...) and setTargetObject(...) (or both <property name='targetClass'> and <property name='targetObject'> in XML). afterPropertiesSet checks both non-null and throws before any field lookup.

Common situations: XML bean definition that fills both targetClass and targetObject by mistake; copy-paste of a working config where one property should have been removed; programmatic GenericBeanDefinition setting both via fluent API; @Bean returning a FieldRetrievingFactoryBean with both set.

Related errors

AI-assisted analysis of spring-projects/spring-framework@69bf83ad71 (2026-08-09). Data as JSON: /api/errors/8ef9b3a143a3e092. Report an issue: GitHub.

Appendix: source

Thrown at spring-beans/src/main/java/org/springframework/beans/factory/config/FieldRetrievingFactoryBean.java:164

	 * nor "targetField" have been specified.
	 * This allows for concise bean definitions with just an id/name.
	 */
	@Override
	public void setBeanName(String beanName) {
		this.beanName = StringUtils.trimAllWhitespace(BeanFactoryUtils.originalBeanName(beanName));
	}

	@Override
	public void setBeanClassLoader(ClassLoader classLoader) {
		this.beanClassLoader = classLoader;
	}


	@Override
	@SuppressWarnings("NullAway") // Dataflow analysis limitation
	public void afterPropertiesSet() throws ClassNotFoundException, NoSuchFieldException {
		if (this.targetClass != null && this.targetObject != null) {
			throw new IllegalArgumentException("Specify either targetClass or targetObject, not both");
		}

		if (this.targetClass == null && this.targetObject == null) {
			if (this.targetField != null) {
				throw new IllegalArgumentException(
						"Specify targetClass or targetObject in combination with targetField");
			}

			// If no other property specified, consider bean name as static field expression.
			if (this.staticField == null) {
				this.staticField = this.beanName;
				Assert.state(this.staticField != null, "No target field specified");
			}

			// Try to parse static field into class and field.
			int lastDotIndex = this.staticField.lastIndexOf('.');
			if (lastDotIndex == -1 || lastDotIndex == this.staticField.length()) {
				throw new IllegalArgumentException(

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