spring-projects/spring-framework · error · IllegalArgumentException

Property 'target' is required

Error message

Property 'target' is required

What it means

AbstractSingletonProxyFactoryBean (parent of TransactionProxyFactoryBean etc.) requires a 'target' object - the bean to be wrapped by the proxy. afterPropertiesSet() (line 137) throws if target is still null, because a proxy with nothing to delegate to is meaningless. This is a configuration-completeness check fired by the InitializingBean callback.

Solutions

1. Call setTarget(targetObject) (or <property name="target" ref="myServiceBean"/> in XML) so the factory has a non-null target
2. Confirm the target bean itself is defined and not returning null
3. Re-check the factory bean definition after any config refactor to ensure target is still wired

Example fix

// before
TransactionProxyFactoryBean fb = new TransactionProxyFactoryBean();
fb.setTransactionManager(txManager);
fb.afterPropertiesSet();

// after
TransactionProxyFactoryBean fb = new TransactionProxyFactoryBean();
fb.setTarget(myService);
fb.setTransactionManager(txManager);
fb.afterPropertiesSet();

// Programmatic config: validate before afterPropertiesSet()
if (factoryBean.getTarget() == null) {
  throw new IllegalStateException("target is required on " + factoryBean.getClass().getSimpleName());
}

private static boolean hasTarget(AbstractSingletonProxyFactoryBean fb) {
  return fb != null && fb.getTarget() != null;
}

When it happens

Trigger: Defining a TransactionProxyFactoryBean (or similar subclass) without setting the target property; programmatic config that forgot setTarget(...); XML missing the <property name="target" .../>.

Common situations: Migrating from ProxyFactoryBean and forgetting the target wiring; a refactored @Bean method that builds the factory bean but drops the setTarget call; XML where the target ref element was accidentally removed.

Related errors

• Property 'methodName' is required
• Property 'targetBeanName' is required
• 'target' needs to be a bean reference, not a bean name as…
• Both 'constructorArgs' and 'constructorArgTypes' need to be…
• Can't determine type of bean with name

AI-assisted analysis of spring-projects/spring-framework@69bf83ad71 (2026-08-09). Data as JSON: /api/errors/6784f9c9a8b7b5e8. Report an issue: GitHub.

Appendix: source

Thrown at spring-aop/src/main/java/org/springframework/aop/framework/AbstractSingletonProxyFactoryBean.java:138

	 * containing BeanFactory for loading all bean classes. This can be
	 * overridden here for specific proxies.
	 */
	public void setProxyClassLoader(ClassLoader classLoader) {
		this.proxyClassLoader = classLoader;
	}

	@Override
	public void setBeanClassLoader(ClassLoader classLoader) {
		if (this.proxyClassLoader == null) {
			this.proxyClassLoader = classLoader;
		}
	}


	@Override
	public void afterPropertiesSet() {
		if (this.target == null) {
			throw new IllegalArgumentException("Property 'target' is required");
		}
		if (this.target instanceof String) {
			throw new IllegalArgumentException("'target' needs to be a bean reference, not a bean name as value");
		}
		if (this.proxyClassLoader == null) {
			this.proxyClassLoader = ClassUtils.getDefaultClassLoader();
		}

		ProxyFactory proxyFactory = new ProxyFactory();

		if (this.preInterceptors != null) {
			for (Object interceptor : this.preInterceptors) {
				proxyFactory.addAdvisor(this.advisorAdapterRegistry.wrap(interceptor));
			}
		}

		// Add the main interceptor (typically an Advisor).
		proxyFactory.addAdvisor(this.advisorAdapterRegistry.wrap(createMainInterceptor()));

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