How to define a statement as sink

[akanksha1331]

/**
 * @name snk117
 * @kind problem
 * @problem.severity warnings
 * @id java/example/sink-detection
 */

 import java
 import semmle.code.java.dataflow.DataFlow
 
 predicate isSink(DataFlow::Node snk) {
    ......
  )
 }
 
 // Query to output each detected sink with its package, class, function declaration, and signature
 from DataFlow::Node sink
 where isSink(sink)
 select sink,
   "Sink element in type: " + sink.getEnclosingCallable().getDeclaringType().getName() + ", method: "
     + sink.getEnclosingCallable().getName() + ", signature: " +
     sink.getEnclosingCallable().getQualifiedName() + "(" +
     sink.getEnclosingCallable().getSignature() + ")" + ", sink data type: " +
     sink.getType().getName()
 

What should my predicate be in order to detect the follwoing taint sink?

nextView = "redirect:" + target;

The nextView variable can include the unvalidated target parameter/

[aibaars]

I suppose you'd like to treat + expressions with the string literal "redirect:" on the left side as a sink. The classes for those types of expressions are AddExpr, and StringLiteral.