Python-inspired method decorator for Groovy.
// Guard.groovy in its own project
import com.github.yihtserns.groovy.decorator.MethodDecorator
import com.github.yihtserns.groovy.decorator.Function
import org.codehaus.groovy.transform.GroovyASTTransformationClass
import java.lang.annotation.Retention
import java.lang.annotation.RetentionPolicy
import java.lang.annotation.Target
import java.lang.annotation.ElementType
@MethodDecorator({ Function func ->
return { args ->
String username = args[0]
if (username == 'hacker') {
throw new UnsupportedOperationException("hacker not allowed")
} else {
func(args) // Call original method
}
}
})
@GroovyASTTransformationClass("com.github.yihtserns.groovy.decorator.DecoratorASTTransformation")
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@interface Guard {
}// SomeScript.groovy
class SomeOperation {
@Guard
public String doStuff(String username, int secretCode) {
println "${username}: ${secretCode}"
}
}
def op = new SomeOperation()
op.doStuff('good guy', 3) // prints 'good guy: 3'
op.doStuff('hacker', 1) // throws UnsupportedOperationException// Guard.groovy in its own project
import com.github.yihtserns.groovy.decorator.MethodDecorator
import com.github.yihtserns.groovy.decorator.Function
import org.codehaus.groovy.transform.GroovyASTTransformationClass
import java.lang.annotation.Retention
import java.lang.annotation.RetentionPolicy
import java.lang.annotation.Target
import java.lang.annotation.ElementType
@MethodDecorator({ Function func, Guard guard ->
String[] prohibited = guard.against()
return { args ->
String username = args[0]
if (prohibited.contains(username)) {
throw new UnsupportedOperationException("$username not allowed")
} else {
func(args) // Call original method
}
}
})
@GroovyASTTransformationClass("com.github.yihtserns.groovy.decorator.DecoratorASTTransformation")
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@interface Guard {
String[] against() default ['hacker']
}// SomeScript.groovy
class SomeOperation {
@Guard
public String doStuff(String username, int secretCode) {
println "${username}: ${secretCode}"
}
@Guard(against = ['good guy', 'hacker'])
public String doSuperSensitiveStuff(String username, int secretCode) {
println "${username}: ${secretCode}"
}
}
def op = new SomeOperation()
op.doStuff('admin', 10) // prints 'admin: 10'
op.doStuff('good guy', 3) // prints 'good guy: 3'
op.doStuff('hacker', 1) // throws UnsupportedOperationException
op.doSuperSensitiveStuff('admin', 10) // prints 'admin: 10'
op.doSuperSensitiveStuff('good guy', 3) // throws UnsupportedOperationException
op.doSuperSensitiveStuff('hacker', 1) // throws UnsupportedOperationException// SomeScript.groovy
import com.github.yihtserns.groovy.decorator.Intercept
import com.github.yihtserns.groovy.decorator.Function
class SomeOperation {
@Intercept({ Function func, args ->
String username = args[0]
if (username == 'hacker') {
throw new UnsupportedOperationException("hacker not allowed")
} else {
func(args) // Call original method
}
})
public String doStuff(String username, int secretCode) {
println "${username}: ${secretCode}"
}
}
def op = new SomeOperation()
op.doStuff('good guy', 3) // prints 'good guy: 3'
op.doStuff('hacker', 1) // throws UnsupportedOperationException// SomeScript.groovy
import com.github.yihtserns.groovy.decorator.Intercept
import com.github.yihtserns.groovy.decorator.Function
class SomeOperation {
@Intercept(BlockHacker)
public String doStuff(String username, int secretCode) {
println "${username}: ${secretCode}"
}
@Intercept(BlockHacker)
public String doAnotherStuff(String username, int secretCode) {
println "${username}: ${secretCode}"
}
private static class BlockHacker extends Closure {
BlockHacker(owner, thisObject) {
super(owner, thisObject)
}
def doCall(Function func, args) {
String username = args[0]
if (username == 'hacker') {
throw new UnsupportedOperationException("hacker not allowed")
} else {
func(args) // Call original method
}
}
}
}
def op = new SomeOperation()
op.doStuff('admin', 10) // prints 'admin: 10'
op.doStuff('good guy', 3) // prints 'good guy: 3'
op.doStuff('hacker', 1) // throws UnsupportedOperationException
op.doAnotherStuff('admin', 10) // prints 'admin: 10'
op.doAnotherStuff('good guy', 3) // prints 'good guy: 3'
op.doAnotherStuff('hacker', 1) // throws UnsupportedOperationException| Description | |
|---|---|
Function.name : String |
Name of the decorated method. |
Function.returnType : Class<?> |
Return type of the decorated method. |
The way it works is similar to groovy.transform.Memoized, in that it turns:
class MyClass {
@Decorator1(el1 = val1, el2 = val2,... elN = valN)
@Decorator2
boolean method(String x, int y) {
...
}
@Decorator1
String method(x.Input input1, y.Input input2) {
...
}
@Decorator1
String method(y.Input input1, x.Input input2) {
...
}
}into:
class MyClass {
private Function decorating$methodStringint = Function.create({ String x, int y -> decorated$method(x, y) }, boolean)
.decorateWith(
/** Decorator1 annotated on method(String, int) **/,
/** Decorator1's decorator closure **/)
.decorateWith(
/** Decorator2 annotated on method(String, int) **/,
/** Decorator2's decorator closure **/)
private Function decorating$methodInputInput = Function.create({ x.Input input1, y.Input input2 -> decorated$method(input1, input2) }, String)
.decorateWith(
/** Decorator1 annotated on method(x.Input, y.Input) **/,
/** Decorator1's decorator closure **/)
private Function _decorating$methodInputInput = Function.create({ y.Input input1, x.Input input2 -> decorated$method(input1, input2) }, String)
.decorateWith(
/** Decorator1 annotated on method(y.Input, x.Input) **/,
/** Decorator1's decorator closure **/)
@Decorator1(el1 = val1, el2 = val2,... elN = valN)
@Decorator2
boolean method(String x, int y) {
decorating$methodStringint([x, y])
}
private boolean decorated$method(String x, int y) {
...
}
@Decorator1
String method(x.Input input1, y.Input input2) {
decorating$methodInputInput([input1, input2])
}
private String decorated$method(x.Input input1, y.Input input2) {
...
}
@Decorator1
String method(y.Input input1, x.Input input2) {
_decorating$methodInputInput([input1, input2])
}
private String decorated$method(y.Input input1, x.Input input2) {
...
}
}@Decorator1 // Decorate with this first, then
@Decorator2 // Decorate with this, then
@Decorator3 // Decorate with this
String getSecret(user, secretId) {
...
}Example:
@Allow(Role.FIELD_AGENT)
@CacheResult
@Log(entry=true, exit=true)
String getSecret(user, secretId) {
...
}
...
getSecret('707', 707) // -> Log -> CacheResult -> Allow -> greet(user, secretId)An exception will be thrown:
java.lang.ArrayIndexOutOfBoundsException: Internal compiler error while compiling script1457454321240940813275.groovy
Method: MethodNode@1527752119[java.lang.Object doCall(java.lang.Object)]
Line -1, expecting casting to java.lang.Object but operand stack is empty
at org.codehaus.groovy.classgen.asm.OperandStack.doConvertAndCast(OperandStack.java:323)
at org.codehaus.groovy.classgen.asm.OperandStack.doGroovyCast(OperandStack.java:290)
...