Project Wonder is chocked so full of WebObjects goodness that it is hard to envision developing a project without it. Here are three bits that I use all the time.

Autolocking EditingContexts

Step one: Learn WebObjects

Step two: Realize that using the session().defaultEditingContext() exclusively is bad.

Step three: Start using multiple EOEditingContexts.

Step four: Read, re-read, then read again the documentation on EC locking.

Step five: Encounter production deadlocks.

Step six: Cry.

Thankfully Project Wonder provides an amazing solution in the form of autolocking EditingContexts. Enabling them is simple. Set some properties for your project:

er.extensions.ERXApplication.useEditingContextUnlocker=true
er.extensions.ERXEC.defaultAutomaticLockUnlock=true
er.extensions.ERXEC.useSharedEditingContext=false
er.extensions.ERXEC.defaultCoalesceAutoLocks=true

There is an email from Mike Schrag with some juicy details here.

Change your code so that you never call new EOEditingContext(); instead use the ERXEC.newEditingContext() factory method.

ERXThreadStorage

Problem: You need access to an object in your session from an EO. Maybe you want to set a “createdBy” value to the current user in awakeFromInsertion

Adding a reference to the Session in your EOs would be bad so what are you going to do?

Solution: Use ERXThreadStorage to store a reference to the current user and access that from your EO.

In your Session.java:

public User currentUser; // assume exists

public void awake() {
    super.awake();
    ERXThreadStorage.takeValueForKey(currentUser, "currentUser");
}

In your EO.java:

public void awakeFromInsertion(EOEditingContext ec) {
    super.awakeFromInsertion(ec);
    User user = ERXThreadStorage.valueForKey("currentUser"));
    if (user != null) {
        setCreatedBy(user.userName);
    }
}

ERXGenericRecord

ERXGenericRecord is another Project Wonder class that is full of yumminess. Please read the API docs for the full details, but here are a few of my favorites:

willUpdate(); // called after saveChanges() but before validation
              // so it is safe to make changes. See the rest of
              // will* and did* methods for more

primaryKey(); // returns the primary key (null if the EO hasn't
              // been saved yet)

primaryKeyInTransaction(); // returns the primary key as above,
              // but if the EO hasn't beens saved yet, it'll
              // figure out what the pk should be, return it,
              // cache it, and use it later when the EO does get
              // saved. Very cool.

There is much, much more: ERXLocalizer, ERJavaMail, ERExcelLook… Dive into the docs and I’m sure you’ll find something usefull.