Tips and Tricks while working with Groovy

This document contains the Code snippet taken from the Commit notification.
Most of tricks on Groovy are taken from the code committed by Scott Gray , Joe Eckard , Marco Risaliti and others.

Groovy Goodies  

1. Start the name of groovy file from capital letter and then follow the camel case pattern.For example "PendingCommunications.groovy".
    The reason behind is shown below (Comments from Joe on Developer Mailing List) :
   • The main reason for this is that when a script is run without a class declaration, the filename is used to create the class name and you can experience problems with untyped variables. For example, a script named product.groovybecomes class "product", and if the script contains an untyped variable "product", it assumes you're trying to access the class "product" instead of a new variable "product".
   • A secondary reason would be consistency, as some scripts have already been named this way. (EditProductFeatures.groovy, etc.

• Primary Key Definition
  Beanshell :
    productAssoc = delegator.findByPrimaryKey("ProductAssoc", UtilMisc.toMap("productId", productId, "productIdTo", productIdTo, "productAssocTypeId", productAssocTypeId, "fromDate", fromDate));
  Groovy :
    Pre EntityQuery : productAssoc = delegator.findByPrimaryKey("ProductAssoc", ['productId' : productId, 'productIdTo' : productIdTo, 'productAssocTypeId' : productAssocTypeId, 'fromDate' : fromDate]);
    Post EntityQuery : productAssoc = from("ProductAssoc").where("productId", productId, "productIdTo", productIdTo, "productAssocTypeId", productAssocTypeId, "fromDate", fromDate).queryOne()
  

1. Null check
   Beanshell :
     if (payment == null) continue;
   Groovy :
     if (!payment) continue;
2. Null + Size greater then Zero Check
   Beanshell :
     if (glAccounts != null && glAccounts.size() > 0) {
   Groovy :
     if (glAccounts) {
3. One line assignment
   Beanshell : 
     nowDate = UtilDateTime.nowDate();
     context.put("nowDate", nowDate);
   Groovy :
     context.nowDate = UtilDateTime.nowDate();
   Note : Sentence can be kept in single line with the usage of DOT (.) for putting some values in context.
4. Beanshell :
     String nowTimestampString = UtilDateTime.nowTimestamp().toString();
   Groovy :
     context.nowTimestampString = UtilDateTime.nowTimestamp().toString();
   Note : No need to specify the object type.
5. No need to specify semicolon
   Beanshell :
       import org.ofbiz.product.inventory.InventoryWorker;
   Groovy :
     import org.ofbiz.product.inventory.InventoryWorker
   Note : We can remove the semicolon in groovy import syntax. Always import the files that are being used in Groovy files instead of importing all the files from the package.
6. Beanshell :
     List allTypes = new LinkedList();
     i = invoiceItemTypes.iterator();
     while ( i ) {
     GenericValue invoiceItemType = i.next();
   Groovy :
      invoiceItemTypes.each {
     GenericValue invoiceItemType = it;
   or
       invoiceItemTypes.each { invoiceItemType ->
7. Beanshell :
     invoiceAppls = delegator.findByAnd("PaymentApplication", UtilMisc.toMap("invoiceId", invoiceId, "invoiceItemSeqId", null)); 
   Groovy :
      Pre EntityQuery : invoiceAppls = delegator.findByAnd("PaymentApplication", [invoiceId : invoiceId, invoiceItemSeqId : null]);
      Post EntityQuery : invoiceAppls = invoice.getRelated("PaymentApplication", [invoiceItemSeqId : null], null, false)
   Empty Map example
   Beanshell :
      product = new HashMap(); // Empty map  
   Groovy :
     product = [:] ;

8. Empty  List example
   Beanshell :
     products = new ArrayList(); // Empty list  
   Groovy :
     products = [] ; 

   Important Note

   This is pretty cool, groovy coerces objects into booleans:
   An empty string,list,map = false otherwise true
   An iterator with no more elements = false otherwise true
   null = false

9. Beanshell :
     while (iter.hasNext()) {
   Groovy :
      while (iter) {
   Note : Another alternate of while statement is the usage of "each" on the list values.
10. List example
    Beanshell :
      if (UtilValidate.isNotEmpty(invoiceItemTypeOrgs)) {
    Groovy :
      if (invoiceItemTypeOrgs) {
    Note : Not empty list returns true.
11. Map Example.
    Beanshell :
      if (UtilValidate.isNotEmpty(invoiceItemTypeOrgs)) {
    Groovy :
      if (invoiceItemTypeOrgs) {
    Note : Not empty Map returns true.
12. String Example
    Beanshell :
      if (paymentId != null) {
    Groovy :
       if (paymentId) {
    Note : Not empty String returns true.
13. Beanshell :
      invoiceId = parameters.get("invoiceId");
    Groovy :
       invoiceId = parameters.invoiceId; 
    Note : The value coming from parameters map should be considered as String.Other types should be explicitly specified.
14. Elvis Operator : If any string return empty or null value then we can put Default value with the help of Elvis Operator ( ?: ) .Its short form of Java Ternary Operator.
    Beanshell :
      invoiceType = parameters.get("invoiceTypeId");
      if (invoiceType == null) invoiceType = "ANY";
    Groovy :
      invoiceType = parameters.invoiceTypeId ?: "ANY" ;
15. Some important files that are responsible for Groovy handling in OFBiz.
    a) GroovyUtil.java
    b) GroovyServiceTest.groovy
    c)  GroovyEngine.java
    d) ModelFormAction.java