apex:messages vs required=true

Question

I have a requirement where at some places in the visual force page, there should be required fields so I have put this :

<apex:inputfield id="selectId"  value="{!var.field1__c}" required="true" styleclass="mystyle" />

Later I have a custom validation in the controller class that if {!var.field2__c} (That I use to show) is greater than 200, I throw a custom exception (class that extends Exception class) catch it and capture it in <apex:messages styleClass="error_Style" />

Catch(Exception ex) { ApexPages.addMessages(ex) ; }

The thing what is happening is, when i put field1_c empty and field2_c as some value greater than 200 (ex: 300); I get only the required=true error message and not the custom page message that I have. Can anyone tell why is the required error message overriding my custom message? Thanks

Answer 1

It does't overriding your message. It is just the first exception that occure.

Triggers and Order of Execution on the server, Salesforce:

Loads the new record field values from the request and overwrites the old values.
 If the request came from a standard UI edit page, Salesforce runs system validation to check the record for:
    -Compliance with layout-specific rules
    -Required values at the layout level and field-definition level
    -Valid field formats
    -Maximum field length
 Salesforce doesn't perform system validation in this step when the request comes from other sources, such as an Apex application or a SOAP API call.