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# 2. The designator reference

Generated by [`DesignatorAspect`](../src/main/java/com/ankurm/aop/aspect/DesignatorAspect.java)
and [`PointcutParserEndpoint`](../src/main/java/com/ankurm/aop/web/PointcutParserEndpoint.java).
Transcript: [`01-designators.txt`](output/01-designators.txt).

## Supported

| Designator | Matches on | Evaluated | Cost |
|---|---|---|---|
| `execution(...)` | method signature | statically | cheap |
| `within(Type)` | the declaring type | statically | cheap |
| `this(Type)` | the **proxy**'s type | at runtime | per call |
| `target(Type)` | the **target object**'s type | at runtime | per call |
| `args(Types)` | argument runtime types; can bind | at runtime | per call |
| `@target(Ann)` | annotation on the executing object's class | at runtime | per call |
| `@args(Ann)` | annotation on argument runtime types | at runtime | per call |
| `@within(Ann)` | annotation on the declaring type | statically | cheap |
| `@annotation(Ann)` | annotation on the method | statically | cheap |
| `bean(name)` | Spring bean name, wildcards allowed | — | cheap |

`bean(...)` is Spring's own; it does not exist in AspectJ.

The runtime group cannot be decided from the signature alone, so Spring must check on every
candidate invocation. Prefer the static equivalent where one exists: `@within` instead of
`@target`, `within` instead of `this`, when the distinction does not matter.

## What each one actually matched here

```
  execution (full signature)       -> DefaultOrderService.place(..)
  execution (wildcards)            -> DefaultOrderService.cancel(..)
  within                           -> InventoryService.reserve(..)
  this(OrderService)               -> place, cancel, interfaceless
  target(DefaultOrderService)      -> place, cancel, interfaceless
  args (bound: SKU-1/2)            -> DefaultOrderService.place(..)
  @target(Audited)                 -> DefaultOrderService.cancel(..)
  @args(Trackable)                 -> DefaultOrderService.interfaceless(..)
  @within(Audited)                 -> DefaultOrderService.place(..)
  @annotation(Marker)              -> DefaultOrderService.place(..)
  bean(inventoryService)           -> InventoryService.reserve(..)
  bean(*OrderService)              -> place, cancel, interfaceless
```

`InventoryService.finalCheck` was called and appears nowhere: it is `final`, so no proxy could
override it. That is [failure 4](05-broken-aspect-gallery.md).

## Not supported

`call`, `get`, `set`, `preinitialization`, `staticinitialization`, `initialization`, `handler`,
`adviceexecution`, `withincode`, `cflow`, `cflowbelow`, `if`, `@this`, `@withincode`.

All fourteen were fed to the parser. All fourteen were rejected, with:

```
org.aspectj.weaver.tools.UnsupportedPointcutPrimitiveException
Pointcut expression 'call(* ...place(..))' contains unsupported pointcut primitive 'call'
```

**The reference documentation says these throw `IllegalArgumentException`. They do not.**
`UnsupportedPointcutPrimitiveException extends RuntimeException` directly — checked with
`javap`, pinned by `AopContractTests.unsupportedDesignatorExceptionType`. A
`catch (IllegalArgumentException)` will not catch it.

## When the failure happens

`setExpression(...)` only stores the string. The expression is not parsed or validated until
something asks it to match. An unsupported designator therefore fails at the first candidate
invocation, not at startup — so a rarely-exercised aspect can ship broken.

## Combining and naming

`&&`, `||` and `!` compose designators. Name the result rather than repeating it:

```java
@Pointcut("within(com.ankurm.aop.service..*)")
public void inServiceLayer() {}

@Before("this(OrderService) && inServiceLayer()")
public void advice(JoinPoint jp) { }
```

A named pointcut is referenced by its method name and is the single biggest readability win
available here.