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Apex Design PatternsDevelopers
Richard Vanhook and Dennis Thong@richardvanhook @denniscfthong
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Safe HarborSafe harbor statement under the Private Securities Litigation Reform Act of 1995: This presentation may contain forward-looking statements that involve risks, uncertainties, and assumptions. If any such uncertainties materialize or if any of the assumptions proves incorrect, the results of salesforce.com, inc. could differ materially from the results expressed or implied by the forward-looking statements we make. All statements other than statements of historical fact could be deemed forward-looking, including any projections of product or service availability, subscriber growth, earnings, revenues, or other financial items and any statements regarding strategies or plans of management for future operations, statements of belief, any statements concerning new, planned, or upgraded services or technology developments and customer contracts or use of our services. The risks and uncertainties referred to above include – but are not limited to – risks associated with developing and delivering new functionality for our service, new products and services, our new business model, our past operating losses, possible fluctuations in our operating results and rate of growth, interruptions or delays in our Web hosting, breach of our security measures, the outcome of any litigation, risks associated with completed and any possible mergers and acquisitions, the immature market in which we operate, our relatively limited operating history, our ability to expand, retain, and motivate our employees and manage our growth, new releases of our service and successful customer deployment, our limited history reselling non-salesforce.com products, and utilization and selling to larger enterprise customers. Further information on potential factors that could affect the financial results of salesforce.com, inc. is included in our annual report on Form 10-K for the most recent fiscal year and in our quarterly report on Form 10-Q for the most recent fiscal quarter. These documents and others containing important disclosures are available on the SEC Filings section of the Investor Information section of our Web site. Any unreleased services or features referenced in this or other presentations, press releases or public statements are not currently available and may not be delivered on time or at all. Customers who purchase our services should make the purchase decisions based upon features that are currently available. Salesforce.com, inc. assumes no obligation and does not intend to update these forward-looking statements.
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Richard VanhookSenior Technical Solution Architect@richardvanhook
Dennis ThongDirector - Technical Solution Architect@denniscfthong
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The PlanCover four design patterns
▪ Problem▪ Pattern Abstract▪ Code
Your participation is encouraged!
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Patterns1. ?2. ?3. ?4. ?
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Meet Billy, Your Admin• 3+ yrs as Salesforce Admin• Just recently started coding• Sad because of this:
• Needs your help!
Trigger.AccountTrigger: line 3, column 1System.LimitException: Too many record type describes: 101
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The Offending Code
• When a single Account is inserted, what happens?• When 200+ Accounts are inserted…?
trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = new AccountFooRecordType(); .... }}
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public class AccountFooRecordType { public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); }}
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Solution: Singleton
Singleton
- instance : Singleton
- Singleton()+ getInstance() : Singleton
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Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = new AccountFooRecordType(); .... }}
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public class AccountFooRecordType { public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); }}
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• Above is the offending code again• Changes are highlighted in next slides
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Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = (new AccountFooRecordType()).getInstance(); .... }}
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public class AccountFooRecordType { public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); } public AccountFooRecordType getInstance(){
return new AccountFooRecordType(); }}
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Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = AccountFooRecordType.getInstance(); .... }}
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public class AccountFooRecordType { public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); } public static AccountFooRecordType getInstance(){
return new AccountFooRecordType(); }}
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Static▪ Can modify member variables, methods, and blocks▪ Executed when?
• When class is introduced (loaded) to runtime environment
▪ How long does that last in Java?• Life of the JVM
▪ In Apex?• Life of the transaction
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Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = AccountFooRecordType.getInstance(); .... }}
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public class AccountFooRecordType { public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); } public static AccountFooRecordType getInstance(){
return new AccountFooRecordType(); }}
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Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = AccountFooRecordType.getInstance(); .... }}
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public class AccountFooRecordType { public static AccountFooRecordType instance = null; public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); } public static AccountFooRecordType getInstance(){ if(instance == null) instance = new AccountFooRecordType(); return instance; }}
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Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = AccountFooRecordType.getInstance(); .... }}
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public class AccountFooRecordType { private static AccountFooRecordType instance = null; public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); } public static AccountFooRecordType getInstance(){ if(instance == null) instance = new AccountFooRecordType(); return instance; }}
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Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = AccountFooRecordType.getInstance(); .... }}
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public class AccountFooRecordType { private static AccountFooRecordType instance = null; public String id {get;private set;} private AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); } public static AccountFooRecordType getInstance(){ if(instance == null) instance = new AccountFooRecordType(); return instance; }}
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Patterns1. Singleton2. ?3. ?4. ?
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geocode('moscone center') //=> 37.7845935,-122.3994262
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Your Suggestion to Billypublic class GoogleMapsGeocoder{ public static List<Double> getLatLong(String address){ //web service callout of some sort return new List<Double>{0,0}; }}
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But then Billy mentions these requirements▪ Need other options besides Google Maps▪ Allow client code to choose provider
System.debug(GoogleMapsGeocoder.getLatLong('moscone center'));//=> 13:56:36.029 (29225000)|USER_DEBUG|[29]|DEBUG|(0.0, 0.0)
0708
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Solution: Strategy
defines a family of algorithms, encapsulates each one, and makes them interchangeable▪ Context => Geocoder▪ operation() => getLatLong()▪ Strategy => GeocodeService▪ ConcreteStrategyA => GoogleMapsImpl▪ ConcreteStrategyB => MapQuestImpl
Context
+operation()
Strategy
+operation()
ConcreteStrategyA
+operation()
Clientstrategies
*1
ConcreteStrategyB
+operation()
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Let’s Code Itpublic interface GeocodeService{ List<Double> getLatLong(String address);}
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public class GoogleMapsImpl implements GeocodeService{ public List<Double> getLatLong(String address){ return new List<Double>{0,0}; }}
public class MapQuestImpl implements GeocodeService{ public List<Double> getLatLong(String address){ return new List<Double>{1,1}; }}
0405060708
0910111213
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public class Geocoder { private GeocodeService strategy; public Geocoder(GeocodeService s){ strategy = s; } public List<Double> getLatLong(String address){ return strategy.getLatLong(address); }}
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Geocoder geocoder = new Geocoder(new GoogleMapsImpl());System.debug(geocoder.getLatLong('moscone center'));//=> 13:56:36.029 (29225000)|USER_DEBUG|[29]|DEBUG|(0.0, 0.0)
101112
Geocoder
+ Geocoder(GeocodeService)
+getLatLong(String)
GeocodeService
+getLatLong(String)
GoogleMapsImpl
+getLatLong(String)
Clientstrategies
*1
MapQuestImpl
+getLatLong(String)
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public class Geocoder { public static final Map<String,Strategy> strategies = new Map<String,Strategy>{'googlemaps' => new GoogleMapsImpl() ,'mapquest' => new MapQuestImpl()}; private GeocodeService strategy; public Geocoder(String name){ strategy = strategies.get(name);} public List<Double> getLatLong(String address){ return strategy.getLatLong(address); }}
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Geocoder geocoder = new Geocoder('googlemaps');System.debug(geocoder.getLatLong('moscone center'));//=> 13:56:36.029 (29225000)|USER_DEBUG|[29]|DEBUG|(0.0, 0.0)
111213
Geocoder
+ Geocoder(String)
+getLatLong(String)
GeocodeService
+getLatLong(String)
GoogleMapsImpl
+getLatLong(String)
Clientstrategies
*1
MapQuestImpl
+getLatLong(String)
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public class Geocoder { public class NameException extends Exception{} public static final Map<String,GeocodeService> strategies; static{ GlobalVariable__c gv = GlobalVariable__c.getInstance('strategies'); List<String> strategyNames = new List<String>(); if(gv != null && gv.value__c != null) strategyNames = gv.value__c.split(','); strategies = new Map<String,GeocodeService>(); for(String name : strategyNames){ try{strategies.put(name,(GeocodeService)Type.forName(name+'impl').newInstance());} catch(Exception e){continue;} //skip bad name silently } } private GeocodeService strategy; public Geocoder(String name){ if(!strategies.containsKey(name)) throw new NameException(name); strategy = strategies.get(name); } public List<Double> getLatLong(String address){ return strategy.getLatLong(address); }}
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Patterns1. Singleton2. Strategy3. ?4. ?
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Question
Transient selection checkboxes
Calculated Fields with Updates
How do we extend the functionality of an sObject in Apex without adding new fields?
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Solution – sObject Decorator
(aka Wrapper Classes v2.0)
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Example - ScenarioWeather sObject
▪ City__c▪ TempInFahrenheit__c (in Fahrenheit)
VisualForce Requirements▪ Stored temperature in Fahrenheit is displayed in Celcius▪ User enters Temperature in Celcius and is stored to the record in Fahrenheit
Bi-directional Display and Calculation
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The Code – Decorated sObject Classpublic class DecoratedWeather {
public Weather__c weather { get; private set; }
public DecoratedWeather ( Weather__c weather) { this.weather = weather;
}
public Decimal tempInCelcius { get {
if (weather != null && tempInCelcius == null )tempInCelcius = new Temperature().FtoC(weather.TempInFahrenheit__c);
return tempInCelcius;
} set {
if (weather != null && value != null ) weather.TempInFahrenheit__c= new Temperature().CtoF(value);
tempInCelcius = value;}
}}
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The Code – Custom Controllerpublic class Weather_Controller {
public List<DecoratedWeather> listOfWeather {
get { if (listOfWeather == null) {
listOfWeather = new List<DecoratedWeather>(); for (Weather__c weather : [select name, temperature__c from Weather__c]) {
listOfWeather.add(new DecoratedWeather(weather)); }
} return listOfWeather;
} private set;
}}
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The Code – VisualForce Page<apex:page controller="weather_controller">
<!-- VF page to render the weather records with Ajax that only rerenders the page on change of the temperature
--> <apex:form id="theForm"> <apex:pageBlock id="pageBlock"> <apex:pageBlockTable value="{!listOfWeather}" var="weather"> <apex:column value="{!weather.weather.name}"/> <apex:column headerValue="Temperature (C)"> <apex:actionRegion > <apex:inputText value="{!weather.tempInCelcius}"> <apex:actionSupport event="onchange" reRender="pageBlock"/> </apex:inputText> </apex:actionRegion> </apex:column> <apex:column headerValue="Temperature (F)" value="{!weather.weather.Temperature__c}" id="tempInF"/> </apex:pageBlockTable>
</apex:pageBlock> </apex:form></apex:page>
010203040506070809101112131415161718192021222324 No client side
logic!!!
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Finally, on the VisualForce page
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Patterns1. Singleton2. Strategy3. sObject Decorator4. ?
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Billy Has a New Problem!Billy wrote a trigger to create an order on close of an opportunity,
however:▪ It always creates a new order every time the closed opportunity is
updated▪ When loading via Data Loader, not all closed opportunities result in an
order
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The Offending Codetrigger OpptyTrigger on Opportunity (after insert, after update) {
if (trigger.new[0].isClosed) {Order__c order = new Order__c();…insert order
}}
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No Bulk Handling
Occurs regardless of prior state
Poor reusability
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Any Better?trigger OpptyTrigger on Opportunity (after insert, after update) {
new OrderClass().CreateOrder(trigger.new);
}
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public class OrderClass {
public void CreateOrder(List<Opportunity> opptyList) {for (Opportunity oppty : opptyList) {
if (oppty.isClosed) {Order__c order = new Order__c();...insert order;
}}
}}
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Occurs regardless of prior state
Not bulkified
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How’s this?trigger OpptyTrigger on Opportunity (before insert, before update) {
if (trigger.isInsert) {new OrderClass().CreateOrder(trigger.newMap, null);
elsenew OrderClass().CreateOrder(trigger.newMap, trigger.oldMap);
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public class OrderClass {
public void CreateOrder(Map<Opportunity> opptyMapNewMap<Opportunity> opptyMapOld) {
List<Order__c> orderList = new List<Order__c>();for (Opportunity oppty : opptyMapNew.values()) {
if (oppty.isClosed && (opptyMapOld == null ||!opptyMapOld.get(oppty.id).isClosed)) {
Order__c order = new Order__c();...orderList.add(order);
}}insert orderList ;
}
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This code is highly coupled and not reusable
At least it’s bulkified
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Solution – Bulk Transition
• Checks for eligible records that have changed state and match criteria
• Calls utility class method to perform the work
• Only eligible records are passed in
• Generic utility class method that can be called from any context
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At Last!!!trigger OpptyTrigger on Opportunity (after insert, after update) {
if (trigger.isAfter && (trigger.isInsert || trigger.isUpdate)) {List<Opportunity> closedOpptyList = new List<Opportunity>();for (Opportunity oppty : trigger.new) {
if (oppty.isClosed && (trigger.isInsert || (trigger.isUpdate &&!trigger.oldMap.get(oppty.id).isClosed)))
closedOpptyList.add(oppty);}if (!closedOpptyList.isEmpty())
new OrderClass().CreateOrderFromOpptys(closedOpptyList)
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public class OrderClass {public void CreateOrdersFromOpptys(List<Opportunity> opptyList) {
List<Order__c> orderList = new List<Order__c>();for (Opportunity oppty : opptyList) {
Order__c order = new Order__c();...orderList.add(order);
}insert orderList ;
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Trigger handles state transition
This method is now a lot more reusable and is bulk-
safe
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Patterns1. Singleton2. Strategy3. sObject Decorator4. Bulk State Transition
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ResourcesWrapper Classes - http://wiki.developerforce.com/page/Wrapper_Class Apex Code Best Practices - http://wiki.developerforce.com/page/Apex_Code_Best_Practices Apex Web Services and Callouts - http://wiki.developerforce.com/page/Apex_Web_Services_and_Callouts Sample Code - https://github.com/richardvanhook/Force.com-Patterns
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More at #DF13Apex Enterprise Patterns: Building Strong FoundationsTuesday, November 19th: 12:15 pm - 01:00 pm - Moscone Center West – 2009High Reliability DML and Concurrency Design Patterns for ApexMonday, November 18th: 11:15 am - 12:00 pm - Moscone Center West – 2009Making Your Apex and Visualforce ReusableTuesday, November 19th: 12:15 pm - 01:00 pm - Moscone Center West – 2022Design Patterns for Asynchronous ApexTuesday, November 19th: 05:15 pm - 06:00 pm - Moscone Center West – 2024The Apex Ten CommandmentsWednesday, November 20th: 04:00 pm - 04:45 pm - Moscone Center West - 2006 / 2008
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Speaker Name
Dennis Thong,@denniscfthong
Speaker Name
Richard Vanhook,@richardvanhook
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We want to hear from YOU!
Please take a moment to complete our session survey
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