[CAMEL-12683] When lookup the registry, Camel should support more complex expressions like 'myBean.property'

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Won't Fix
• Affects Version/s: 2.21.1
• Component/s: camel-spring
• Estimated Complexity: Unknown
• Assignee: Zoran Regvart
• Reporter: Christian Ribeaud
• Created: 25/Jul/18 10:28
• Updated: 06/Aug/19 18:45
• Resolved: 06/Aug/19 18:45

Description

Currently, only simple Spring beans lookup is supported, like #myBean. Deeper lookup is currently not supported. As a workaround, you could specify several Spring beans which then maps to the properties of the original bean.
Following code snipped would, for instance, make possible more complex queries:

public class MyApplicationContextRegistry extends ApplicationContextRegistry {

    private final BeanResolver beanResolver;
    private final PropertyAccessor propertyAccessor;
    private final BeanExpressionContext beanExpressionContext;

    MyApplicationContextRegistry(ApplicationContext applicationContext) {
        super(applicationContext);
        beanResolver = new BeanFactoryResolver(applicationContext);
        propertyAccessor = new BeanExpressionContextAccessor();
        beanExpressionContext = createExpressionContext(applicationContext);
    }

    @Override
    public Object lookupByName(final String name) {
        assert name != null : "Unspecified name";
        final ExpressionParser parser = new SpelExpressionParser();
        Expression expression = parser.parseExpression(name);
        Object expressionValue = expression.getValue(createEvaluationContext(), beanExpressionContext);
        return expressionValue;
    }

    private static BeanExpressionContext createExpressionContext(ApplicationContext applicationContext) {
        assert applicationContext instanceof ConfigurableApplicationContext : String.format("MUST be an instance of '%s'.", ConfigurableApplicationContext.class.getName());
        ConfigurableBeanFactory configurableBeanFactory = ((ConfigurableApplicationContext) applicationContext).getBeanFactory();
        return new BeanExpressionContext(configurableBeanFactory, null);
    }

    private EvaluationContext createEvaluationContext() {
        StandardEvaluationContext context = new StandardEvaluationContext();
        context.setBeanResolver(beanResolver);
        context.addPropertyAccessor(propertyAccessor);
        return context;
    }
}

And this code uses out-of-the-box Spring functionalities (I think...).