ofbiz学习笔记--Tips & Tricks while working with Groovy

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.
2.Primary Key Definition
Beanshell :-
-productAssoc = delegator.findByPrimaryKey("ProductAssoc", UtilMisc.toMap("productId", productId, "productIdTo", productIdTo, "productAssocTypeId", productAssocTypeId, "fromDate", fromDate));
Groovy :-
+productAssoc = delegator.findByPrimaryKey("ProductAssoc", ['productId' : productId, 'productIdTo' : productIdTo, 'productAssocTypeId' : productAssocTypeId, 'fromDate' : fromDate]);
Note :- Removed the usage of UtilMis.toMap(). Instead of findByPrimaryKey try to use findOne().
3.Null check
Beanshell :-
  -    if (payment == null) continue;
Groovy :-
+    if (!payment) continue;
4.Null + Size greater then Zero Check
Beanshell :-
-        if (glAccounts != null && glAccounts.size() > 0) {
Groovy :-
+        if (glAccounts) {
5.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.
6.Beanshell :-
- String nowTimestampString = UtilDateTime.nowTimestamp().toString();
Groovy :-
+ context.nowTimestampString = UtilDateTime.nowTimestamp().toString();
Note :- No need to specify the object type.
7.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.

8.Beanshell :-
List allTypes = new LinkedList();
- i = invoiceItemTypes.iterator();
- while ( i ) {
-    GenericValue invoiceItemType = i.next();
Groovy :-
+invoiceItemTypes.each {
+    GenericValue invoiceItemType = it;
or
  +invoiceItemTypes.each { invoiceItemType ->
9.Beanshell :-
-    invoiceAppls = delegator.findByAnd("PaymentApplication", UtilMisc.toMap("invoiceId", invoiceId, "invoiceItemSeqId", null)); 
Groovy :-
+    invoiceAppls = delegator.findByAnd("PaymentApplication", [invoiceId : invoiceId, invoiceItemSeqId : null]);
Note :- Instead of findByAnd() use findList().
10.Empty Map example
Beanshell :-
product = new HashMap(); // Empty map  
Groovy :-
product = [:] ;
11.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
12.Beanshell :-
-while (iter.hasNext()) {
Groovy :-
+while (iter) {
Note :- Another alternate of while statement is the usage of "each" on the list values.
13.List example
Beanshell :-
-    if (UtilValidate.isNotEmpty(invoiceItemTypeOrgs)) {
Groovy :-
+    if (invoiceItemTypeOrgs) {
Note :- Not empty list returns true.
14.Map Example.
Beanshell :-
-    if (UtilValidate.isNotEmpty(invoiceItemTypeOrgs)) {
Groovy :-
+    if (invoiceItemTypeOrgs) {
Note :- Not empty Map returns true.
15.String Example
Beanshell :-
-if (paymentId != null) {
Groovy :-
+if (paymentId) {
Note :- Not empty String returns true.
16.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.
17.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" ;
18.Some important files that are responsible for Groovy handling in OFBiz.
a) GroovyUtil.java
b) GroovyServiceTest.groovy
c)  GroovyEngine.java
d) ModelFormAction.java
e) Some *.jar files that are responsible to run the Groovy scripts are shown below.
   ofbiz/trunk/framework/base/lib/scripting/antlr-2.7.6.jar   (with props)
   ofbiz/trunk/framework/base/lib/scripting/asm-2.2.jar   (with props)
   ofbiz/trunk/framework/base/lib/scripting/asm-analysis-2.2.jar   (with props)
   ofbiz/trunk/framework/base/lib/scripting/asm-tree-2.2.jar   (with props)
   ofbiz/trunk/framework/base/lib/scripting/asm-util-2.2.jar   (with props)
   ofbiz/trunk/framework/base/lib/scripting/groovy-1.5.6.jar   (with props)