.choise()
   .when()
      .simple("${body.messageType} == 105")
          .to(...)
   .when()
      .simple("${body.messageType} == 106")
          .to(...)

package myPackage;

  public enum Code {
     CODE_A("105"),
     CODE_B("106")

     private String value;

    Code(String value) {
        this.value = value;
    }

    public String value() {
        return value;
    }
}

.simple("${body.messageType} == ${type:myPackage.Code.CODE_A.value()}")

.simple("${body.messageType} == ${type:myPackage.Code.CODE_A}")

myPackage.Code.value()

myPackage.Code.CODE_A

.when().groovy("body.messageType == myPackage.CODE_A.value()")

.setHeader("codeA",constant(myPackage.Code.CODE_A.value()))
.setHeader("codeB",constant(myPackage.Code.CODE_B.value()))
.choise()
   .when()
      .simple("${body.messageType} == ${header.codeA}")
          .to(...)
   .when()
      .simple("${body.messageType} == ${header.codeB}")
          .to(...)

//one value
simple(String.format("${body.key} == '%1s'", Code.CODE_A.value())
// multiple values using 'in' operator
simple(String.format("${body.key} in '%1s,%2s'", Code.CODE_A.value(), Code.CODE_B.value())