XML DOM API
This article is intended for plugin writers who create custom web server integrations, or some UI for easy XML editing. It describes the Document Object Model (DOM) in IntelliJ Platform --- an easy way to work with DTD or Schema-based XML models. The following topics will be covered: working with DOM itself (reading/writing tags content, attributes, and subtags) and easy XML editing in the UI by connecting UI to DOM.
It's assumed that the reader is familiar with Java, Swing, IntelliJ Platform XML PSI (classes
XmlTagValue, etc.), IntelliJ Platform plugin development basics (application and project components, file editors).
So, how to operate with XML from an IntelliJ Platform plugin? Usually, one has to take
XmlFile, get its root tag, and then find a required sub-tag by path. The path consists of tag names, each of them a string. Typing these everywhere is tedious and error-prone. Let's assume you have the following XML:
Let's say you want to read the contents of the second bar element, namely, "239".
It's not correct to create chained calls like
because each call here may return
So the code would probably look like this:
Looks awful, doesn't it? But there's a better way to do the same thing. You just need to extend a special interface ---
For example, let's create several interfaces:
Next, you should create a
DomFileDescription object, pass to its constructor the root tag name and root element interface, and register it with extension point
You can now get the file element from
DomManager. To get the "239" value, you only have to write the following code:
I suppose this looks a little bit nicer. You often work with your model in more than one place. Re-creating the model is too inefficient, so we cache it for you, and any subsequent calls to
DomManager.getFileElement() will return the same instance. So, it is useful to invoke this method just once, and then keep everywhere only the "root" object you've obtained. In this case you wont need to repeat that scary first line, and the code will look even nicer.
It is also important to note that with this scenario we avoid potential
NullPointerException: our DOM guarantees that every method accessing a tags child will return a not-null element, even if the correspondingly-named sub-tag doesn't exist. That may seem strange at a first glance, but it appears to be rather convenient. How does it work? Simple. Given those interfaces, DOM generates all code for accessing correct sub-tags and creating model elements at runtime. The sub-tag names and element types are taken from method names, return types and method annotations, if any. In most cases annotations can be omitted, as in our example, but this is discussed further in this article anyway.
Now let us explore more thoroughly what the DOM can do, and look at possible ways of representing various XML concepts such as tag content, attributes or sub-tags. Later we will discuss basic methods for working with the model, as well as cover more advanced functionality. Finally, we'll see how to easily create an UI editor for DOM model elements.
Building the Model
In XML PSI, tag content is referred to as tag value, so well do the same for consistency. To read and change a tag value, you have to add two methods (getter and setter) to your interface, like this:
These method names (
setValue) are standard, and they are used for accessing tag values by default. If you want to use custom method names for the same goal, you should annotate these methods with
@TagValue, for example:
As you can see, our accessors work with
String values. This is natural, since XML represents a text format, and tag content is always text. But sometimes you may want to operate with integers, booleans, enums, or even class names (they, of course, will be represented as
PsiClass ), and more generic Java types (
PsiType ). In such cases, you just need to change the type in methods to the one you need, and everything will keep working correctly.
Custom Value Types
If you operate with even more exotic types, you should tell DOM how to deal with them. First, annotate your accessor methods with the
@Convert annotation, and specify your own class that should extend the
Converter<T> class in the annotation. Here
T is your exotic type, while
Converter<T> is a thing that knows how to convert values between
T. If the value cannot be converted (for example, "foo" is not convertible into
Integer ), the converter may return
null. Please also note that your implementation should have a no-argument constructor.
Let us consider an interesting case when
T represents an enum value. Usually, the converter just searches for enum elements with the names specified in XML. But sometimes, for their names, you may need or want to use values that are not valid Java identifiers. For example, CMP version in EJB may be "1.x" or "2.x", but you can't create Java enums with such names. For such cases, let your enum implement
NamedEnum interface, and then name your enum elements as you wish. Now, just provide the
getValue() implementation that will return the right value to match with XML contents, and voilà! In our example, the code will look as follows:
As we have already mentioned, an XML tag may have lots of artifacts besides its value: there can be attributes, children, but rather often (e.g., according to DTD or Schema) it should have only the value. Of course such tags also need a DOM element to associate with. And we provide such an element:
So, you can just specify a particular
T when using this interface --- and everything will work. Methods that work with
String are provided for many reasons. For example, your
PsiClass. It would be useful to highlight invalid values in UI. To get the value to highlight (the string from the XML file) we have the
getStringValue() method. The error message will be taken from the converter via
Attributes are also rather simple to deal with. You can read their values, set them, and operate with different types. So it's natural to create something like
GenericDomValue<T> and then work as usual. "Something like" will be an inheritor, as shown below:
Consider that you want to work with an attribute named some-class having a value of type
That's all! Now you can get/set values, resolve this
PsiClass, get its
String representation, etc. The name of the attribute will be taken from the method name (see next paragraph). If you name your method in a special way, you can even omit the annotation. For example:
DomNameStrategy interface specifies how to convert accessor names to XML element names. Or more precisely, not the full accessor names, but rather the names minus any "get", "set" or "is" prefixes. The strategy class is specified in the
@NameStrategy annotation in any DOM element interface. Then any descendants and children of this interface will use this strategy. The default strategy is
HyphenNameStrategy, where words are delimited by hyphens (see sample above). Another common variant is
JavaNameStrategy that capitalizes the first letter of each word, as in Java's naming convention. In our example, the attribute name would be "someClass".
If attribute doesn't define a
PsiClass, but some other custom
T that needs a converter, you just need to specify the
@Convert annotation to the getter.
Please note that the attributes getter method will never return
null, even if the attribute isn't specified in XML. Its
getXmlAttribute() methods will return
null, but the DOM interface instance will exist and be valid. If the element has an underlying attribute, this can be easily fixed (surely, only if you need that): just call the
undefine() method (defined in
DomElement ), and the XML attribute disappears, while
GenericAttributeValue remains valid.
Children: Fixed Number
You may often deal with tags that have at most one sub-tag with the given name (e.g.
<cmp-field>) in tags defining entity EJBs. To work with such children, provide getters for them. These getters should have a return type that extends
There's also an annotation to designate such children explicitly:
@SubTag. Its "value" attribute contains a tag name. If it is not specified, the name is implied from the method name using the current name strategy.
Sometimes it is the sub-tag's presence that means something, rather than its content ---
<unchecked> in EJB method permissions, for example. If it exists, then permissions are unchecked, otherwise checked. For such things one should create a special
GenericDomValue<Boolean> child. Usually its
true if there's "true" in a tag value,
false if there's "false" in a tag value, and
null otherwise. In the
@SubTag annotation, you can specify the attribute like
indicator=true. In this case,
getValue() will return
true if the tag exists and
Let's consider another interesting example inspired by EJB, where there is a relation that has two roles, each designating one relation end: first role and second role. Both are represented by tags with the same values. So, we could create a collection of role elements, and every time we access some role we would check if this collection has sufficient number of elements. But one of the main purposes of the DOM is to eliminate unnecessary checks. So why cant we have a fixed (more than one) number of children with the same tag name? Let's have them!
The first method will return the DOM element for the first subtag named
<ejb-relationship-role>, and the second --- for the second one. Hence the term "fixed-number" for such children. According to DTD or Schema, there should be fixed number of subtags with the given name. Most often this fixed number is 1; in our case with the relations it is 2. Just like attributes, fixed-number children exist regardless of underlying tag existence. If you need to delete tags, it can be done with the help of the same
For children of
GenericDomValue type, you can also specify a converter, just as you can for attributes.
One more common case in DTD and Schemas is when children have the same tag name and a non-fixed upper limit in count. Their accessors differ from those of the fixed-number children in the following: the return result is
List of a special type that extends
DomElement, and if you want to use name strategies, the method name must be in pluralized form. For example, in EJB we would have the following method:
There's also an annotation
@SubTagList where you can explicitly specify the tag name.
Returned collections cannot be modified directly. To delete an element from collection, just call
undefine() on this element. The tag will then be removed, and element will become invalid (
DomElement.isValid() == false ). Note that this behavior differs from that of fixed-number children and attributes: they are always valid, even after
undefine(). Again, unlike those children types, collection children always have valid underlying XML tags.
Adding elements is a little bit harder. Since all DOM elements are created internally, you can't just pass some of your DOM elements to some method, to add the element to the collection. In fact, you have to ask a parent element to add a child to the collection. In our example it's done in the following way:
which adds an element to wherever you want, or
which adds a new DOM element to the end of the collection. Please note the singular tense of the word "Entity". That's because here we deal with one
Entity object, while in the collection getter we dealt with potentially many entities.
Now, you can do anything you want with the returned value: modify, define the tag's value, children, etc.
The last common case is also a collection, but one consisting of tags with different names that are arbitrarily mixed. To work with it, you should define collection getters for all tag names within the mixed collection, and then define an additional specially annotated getter:
The annotation here is mandatory - we cannot guess several tag names from one method name.
To add elements to such mixed collections, you should create "add" methods for each possible tag name:
The index parameter in the last example means the index in the merged collection, not in the collection of tags named "bar".
You can extend existing DOM model at runtime by implementing
com.intellij.util.xml.reflect.DomExtender<T>. Register it in "extenderClass" attribute of EP
com.intellij.dom.extender, where "domClass" specifies DOM class
<T> to be extended.
DomExtensionsRegistrar provides various methods to register dynamic attributes and children.
If the contributed elements depend on anything other than plain XML file content (used framework version, libraries in classpath, ...), make sure to return
Generating DOM from Existing XSD
DOM can be generated automatically from existing XSD/DTD. Output correctness/completeness will largely depend on the input scheme and may require additional manual adjustments.
Follow these steps:
Run IntelliJ IDEA with Plugin DevKit enabled in internal mode
Select Tools | Internal Actions | DevKit | Generate DOM Model
Select Scheme file and set options, then click "Generate" to generate sources
Modify generated sources according to your needs
Plugin DevKit supports the following features for working with DOM related code:
Working with the DOM
It often happens that a collection contains same-named tags that may have different structure or even be represented by different types in the DTD or Schema. As an example, JSF Managed Beans may be of three types. If a
<managed-bean> tag contains a
<map-entries> sub-tag, then the Managed Bean type is
MapEntriesBean. If it contains a
<list-entries> sub-tag — can you guess? Right —
ListEntriesBean! Otherwise it's a
PropertyBean (all three interfaces extend
ManagedBean ). And when we write
List<ManagedBean> getManagedBeans(), we expect to get not only a list where all elements are instances of the
ManagedBean interface, but a list where each element is of a certain type, i.e.
In such cases one should decide which interface the DOM element should actually implement (according to the given tag). This is achieved by extending the
TypeChooser abstract class:
Here, the first method (
chooseType()) does exactly what it is named after (chooses the particular type, most often it's a class). The second one (
distinguishTag()) acts in reverse: it modifies a tag so that when the element is read from an XML file next time (for example, after the user has closed and opened the project again), the newly created DOM element will implement the same interface and no model data will be lost. Finally,
getChooserTypes() just returns all the types that could be returned by
To make your
TypeChooser work, register it in your overridden
DomFileDescription.initializeFileDescription() method by calling
Useful Methods of DomElement and DomManager
Of course, DOM is tightly connected to XML PSI, so there's always a way of getting the
XmlTag instance (which can be
null for fixed-number children and attributes) using the
getXmlTag() method. We remember that in
GenericAttributeValue there's also the
getXmlAttribute() method. In general case there is
getXmlElement() method. You can also get a DOM element by its underlying XML PSI element using the
If DOM element has no underlying XML element, it can be created by calling
ensureTagExists(). To delete a tag, use the already known
undefine() method. This method will always delete the underlying XML element (tag or attribute). If the element was a collection child, then neither it nor its entire sub-tree will be valid anymore.
In every normal tree there's always a possibility to walk up.
DomElement is no exception. Method
getParent() just returns element's parent in tree.
<T extends DomElement> T getParentOfType(Class<T> requiredClass, boolean strict) returns the tree ancestor of the given class. You can see the standard strict parameter, that can return the DOM element itself, if it's
false and your current DOM element is an instance of requiredClass.
getRoot() will return the
DomFileElement, which is the root of every DOM tree.
An element becomes invalid if it has been deleted explicitly or due to external PSI changes. Fixed-number children and attributes are meant to stay valid as long as possible, no matter what happens with XML. They can become invalid only if they have collection tree ancestor that has been deleted.
Newly created DOM elements are always correct and valid, so their
isValid() methods will return
Element validity is very important, since you cannot invoke any methods on invalid elements (except, of course,
DOM also has a kind of reflection, called "Generic Info". One would use it to be able to access children by tag names directly, instead of calling getter methods. See
DomGenericInfo interface and
getGenericInfo() methods in
DomManager for more information. There's also
DomElement.getXmlElementName() method that returns the name of a corresponding tag or attribute.
DomElement.getPresentation() returns an instance of
ElementPresentation, an interface that knows presentable element type, name, and sometimes even its icon. Presentations are actually obtained from presentation factory objects that, like ClassChoosers's, should be registered in
ElementPresentationManager as early as possible. You can specify type name and icon for all elements of some class, ways of getting type name, icon and presentable name for particular objects. When not specified, presentable name is taken from the object itself, if it contains a method annotated with
@NameValue annotation, that returns
GenericValue. If there's no such method, it will return
DomElement, there's another way to get this presentable name:
If you want to be notified on every change in the DOM model, add
DomManager. DOM supports the following events: tag value changed, element defined/undefined/changed, and collection child added/removed.
The DOM supports error checking and highlighting. It's based on annotations which you add to the DOM element in a special place (don't confuse these annotations with the ones of Java 5 — they are very different). You need to implement the
DomElementAnnotator interface, and override
DomFileDescription.createAnnotator() method, and create this annotator there. In
DomElementsAnnotator.annotate(DomElement element, DomElementsProblemsHolder annotator) you should report about all errors and warnings in the element's sub-tree to the annotator (
DomElementsProblemsHolder.createProblem() ). You should return this annotator in the corresponding virtual method of the
Automatic Highlighting (BasicDomElementsInspection)
The following errors can be highlighted automatically by providing an instance of
@Requiredelement missing or having empty text
XML value cannot be converted by some
name is not unique while it should be
The latter case requires you to specify the name getter with
@NameValue annotation. The checking uses the
DomFileDescription.getIdentityScope() method to get the element defining the root scope in which the name should be unique.
To suppress spellchecking annotate your DomElement with
There is a common case in error highlighting, when one needs to say, that some required sub-tag or attribute is missing. DOM will do this for you automatically, if you annotate the getter for that child with the
@Required annotation. For collection children getters, this annotation will mean, that the collection should be not empty (corresponding to '+' sign in DTD). Also, when you create a new element that has required fixed-number or attribute children, their tags or attributes will also be created in XML.
Remember the interface
GenericDomValue<T> and its sub-interface
GenericAttributeValue<T>? Remember, that ANY class may be passed as
T — for example, let's interpret
GenericDomValue<PsiClass> as a reference to a class. Then we can always consider it as a reference to an object of class
T! With Strings or enums, it is not a very useful idea, but we'll use it in another way. Very often XML has such a structure that an object is declared at some place, and is referenced at some other place (more precisely, in a tag or attribute value). So, if you want to create a method like
GenericValue<MyDomElement> getMyDomElementReference(), then you just have to specify a proper converter that will find an instance in your model of
MyDomElement with the name specified in the
That's the core idea. Since creating such converters is quite boring, we've done it for you. You don't have to annotate reference getters at all, as the name resolution will be made automatically. Elements will be searched by name, and the name will be taken from the method annotated with
@NameValue. The converter used is
DomResolveConverter. Its constructor takes a parameter, so it can't be referenced in
@Convert annotation, but its subclasses (if you create them) — can. If you still want to specify explicitly that your reference to
DomElement should be resolved "model-wide", use the
@Resolve annotation parameterized with the desired class. The resolution scope will be taken from the
In addition to the above, auto-resolving in DOM also provides some features in your XML text editor: error highlighting, completion, Find Usages, Rename Refactoring... Unresolved references will be highlighted, and even completed. If you want to create a custom converter and want to have this code insight with it, you should extend not only the
ResolvingConverter. It has one more method
getVariants(), where you'll have to provide the collection consisting of all targets your reference may resolve to. Those familiar with
PsiReference will recognize the similarities here.
If you need to choose a
Converter depending on other values (e.g. in sibling/parent element) or any runtime condition (e.g. presence or version of library), you can use
WrappingConverter. See also
GenericDomValueConvertersRegistry for managing an extensible registry of available Converters to choose from.
Mock and Stable Elements
Your DOM elements do not have to be tied to a physical file.
DomManager.createMockElement() will help you to create a virtual element of a given class with the given module. An element may be physical or not. 'Physical' here means that DOM will create a mock document for it, so you can enjoy Undo functionality if you pass this document to the right place in file editor.
DomElement.copyFrom() allows you to copy information from one
DomElement to another. In fact, it just replaces XML tags, and all the old data is lost. Nevertheless, the element's fixed-number children don't become invalid, they only contain new tag values, attribute values, etc. The tree is actually rather conservative.
The combination of
copyFrom() is useful for editing element contents in dialogs. You create a mock copy of an element, work with it in the dialog and then, if the user doesn't cancel, copy the element back to the main model. Since it's a common case, a special shortcut method has been created in
IntelliJ Platform's XML parser is incremental: changes in text do not cause the whole file to be reparsed. But you should keep in mind that this rule may sometimes not work correctly. For example, your DOM elements can unexpectedly become broken as a result of manual editing of the XML file (even if it didn't happen inside those elements). If a file editor depends on such a broken element, this can lead to closing the tab, which isn't very nice from the user's point of view. For example, suppose you have an entity bean named "SomeEntity". You open an editor for it, then you go into the XML, change the tag name from entity to session, and then back to entity. Of course, no DOM element can survive after such blasphemy. But notwithstanding, you still want your editor to stay open! Well, there is a solution, and it's called
DomManager.createStableValue(Factory factory). This method creates a DOM element that delegates all its functionality to some real element (returned from the factory parameter). As soon as that real element becomes invalid, the factory is called once more, and if it returns something valid, it becomes the new delegate. And so on... In the example with EJB, the factory would once again look for an Entity Bean named "SomeEntity".
Stable DOM elements also implement the
StableElement interface, which has the following methods:
DomElement getWrappedElement()— just returns the current element to which all method calls are delegated;
void invalidate()— makes the wrapped element invalid. Any following method call will cause the factory to create a new delegate;
void revalidate()— calls the factory, and if it returns something new (i.e. not the same as the current wrapped element) invalidates the old value and adopts the new one.
Visitor is a very common design pattern. DOM model also has a visitor, and it's called
DomElement interface has methods
acceptChildren() that take this visitor as a parameter. If you look at the interface
DomElementVisitor itself, you may be surprised, since it has only one method:
visitDomElement(DomElement). Where is the Visitor pattern? Where are all those methods with names like
visitT(T) that are usually found in it? There are no such methods, because the actual interfaces (T's) aren't known to anyone except you. But when you instantiate the
DomElementVisitor interface, you may add there these
visitT() methods, and they will be called! You may even name them just
visit(), specify the type of the parameter, and everything will be fine. For example, if you have two DOM element classes —
Bar — your visitor may look like this:
Sometimes you may want to extend your model with some functionality that isn't directly connected with XML, but relates to your program logic. And the most appropriate place for this functionality is the DOM element interface. What to do then?
The simplest case is when you want to add to your interface a method that returns exactly what some other getter in this element (or in one of its children) returns. You can easily write this helper method and annotate it with the
@PropertyAccessor annotation, in which you should specify the path consisting of property names (getter names without the "get" or "is" prefixes). For example, you can write:
In this case, the second method will return just the same as the first one. If there were "foo.bar.name" instead of "very-long-name" in the annotation, the system would actually call
getFoo().getBar().getName() and return the result to you. Such annotations are useful when you're extending some interface that is inconsistent with your model, or you try to extract a common super-interface from two model interfaces with differently named children that have the same sense (see
The case just described is simple, but rare. More often, you really have to incorporate some logic into your model. Then nothing except Java code helps you. And it will. Add the desired methods to your interface, then create an abstract class implementing the interface, and implement there only methods that you added manually and that are not directly connected to your XML model. Note that the class should have a constructor with no arguments.
Now you only have to let DOM know that you wish to use this implementation every time you're creating a model element that should implement the necessary interface. Simply register it using extension point
com.intellij.dom.implementation and DOM will generate at run-time the class that not only implements the needed interface, but also extends your abstract class.
Models Across Multiple Files
Many frameworks require a set of XML configuration files ("fileset") to work as one model, so resolving/navigation works across all related DOM files. Depending on implementation/plugin, providing filesets implicitly (using existing framework's setup in project) or via user configuration (usually via dedicated
Facet) can be achieved.
BaseDomModelFactory for non-
Module scope) and provide implementation of your
DomModel. Usually you will want to add searcher/utility methods to work with your
DomModel implementation. Example can be found in Struts 2 plugin (package
DOM elements can be stubbed, so (costly) access to XML/PSI is not necessary (see Indexing and PSI Stubs for similar feature for custom languages). Performance relevant elements, tag or attribute getters can simply be annotated with
@com.intellij.util.xml.Stubbed. Set and increase
com.intellij.dom.fileMetaData extension whenever you change
@Stubbed annotations usage in your DOM hierarchy to trigger proper rebuilding of Stubs during indexing.
Building a DOM-Based GUI
All forms that deal with DOM are organized in a special way. They support two main things: getting data from XML into the UI, and saving UI data to XML. The former is called resetting, the latter — committing. There's
Committable interface that has corresponding methods:
reset(). There's also a way of structuring your forms into smaller parts, namely the Composite pattern:
reset() are invoked automatically on editor tab switch or undo. So you only need to ensure that all your Swing structure is organized in a tree of
CompositeCommittable, and all the hard work will be done by the IDE.
DOM controls are special descendants of
Committable. All of them implement
DomUIControl. Note that they are not Swing components — they are only a way of connecting DOM model and Swing components. One end of the connection — the DOM element — is usually specified in the controls constructor. The other end — Swing component — can be obtained in 2 ways. The first is to ask DOM control to create it. But that is rather inconvenient if you want to create the forms in, say, IntelliJ IDEA's GUI Designer. In that case, you'll need the second way: ask the control to
bind() to an existing Swing component of a correct type (that depends on the type of value that you're editing). After that, your Swing components will be synchronized with DOM, they'll even highlight errors reported by
Sometimes you may need to do some work (enable or disable some components, change their values) after a particular DOM control is committed. Then you should define the
addCommitListener() method of that DOM control and override the
CommitListener.afterCommit() method. This method will be invoked inside the same write action as the main
commit(), so any changes you do in this method to the XML will be merged with the
commit() in the Undo queue.
With simple controls, you can edit
GenericDomValue: simple text, class names, enums and boolean values. These controls take a special object as a constructor parameter. This object should implement the
DomWrapper interface that knows how to set/get values to/from DOM model.
We have three major DomWrapper's:
DomFixedWrapper<T> redirecting calls to
DomStringWrapper redirecting calls to string accessors of
DomCollectionWrapper that gets/sets values of the first element of the given
GenericDomValue collection. Some controls (those having a text field as part of itself) take additional boolean constructor parameter — commitOnEveryChange, whose meaning is evident from the name. We don't recommend using it anywhere except small dialogs, because committing on every change slows down the system significantly.
Most often these controls are created by
DomUIFactory.createControl(GenericDomValue). This method understands which control to create by using DOM reflection (
DomGenericInfo, as you probably remember). But sometimes you may want to create the controls directly. So let's look at the simple controls more closely.
It allows you to edit boolean values. The control is bound to
The control is bound to a non-editable
JComboBox, so it can be used to choose something from a limited set. One case of such a limited set is enum. Or it can be a constructor where you can provide a
Factory<List<String>>, and return from this factory anything you want (for example, a list of database names to choose from). By default, the wrong values (written in XML, but not present in the list you've given to the control) are displayed in red. Since it's common practice to specify custom
CellRenderer for combo boxes, the control has the
isValidValue(String) method. If it returns
false on the value you're rendering, you can highlight it in some way, to achieve the same result as the default renderer. Or you can just delegate to that renderer in your own way.
Sometimes, when there are only 2 alternatives, it's convenient to use a check box instead of combo box. This control is designed specially for such cases. While being (and being bound to) a check box, the control edits not just "true" or "false", but any two String values, or two enum elements. In the last case, it has a boolean invertedOrder parameter, to specify which element corresponds to the checked state. By default invertedOrder is set to
false, so the first element corresponds to the unchecked state, and the second — to the checked one. If you set the parameter to
true, the states will swap.
Please note that editor-based controls are built on IntelliJ Platform's
Editor instead of standard
JTextField. Since there's currently no way to instantiate Editor directly through the Open API, controls are bound to special
JPanel inheritors, and their
bind() method adds the necessary content to those panels.
This control allows you to edit simple string values. The control is bound to a
TextPanel component. There's also an inheritor of that panel —
MultiLineTextPanel. If you bind a
StringControl to it, a big editor will appear on the screen. In case you don't have space for a big editor, bind it to a
BigTextPanel. Then it will be filled with a text editor, and the browse button will be added to open a dialog with the big editor where you can type a longer string.
This is a one-line editor with a browse button that opens the standard class selection dialog. The control accepts class names only. It is bound to
This is almost the same as PsiClassControl, but allows entering not only class names, but also Java primitive types and even arrays. It is bound to
There is a special table component where each row represents one collection child. It's called
T is your collection element type. To function properly, it needs
DomElement (parent of the collection), some description of the collection (sub-tag name or a
DomCollectionChildDescription from DOM reflection), and a
ColumnInfo array. This can be passed to the constructor, or can be created in a
DomCollectionControl inheritor, in an overriden method
What is a column info? It's just a somewhat more comfortable way to work with the table model. It uses Java 5 generics and is more object-oriented. So, it's named
Item is a type variable corresponding to the type of elements in the collection, and
Aspect is a type variable corresponding to this particular column information type:
Boolean, etc. The basic things that a column knows are: column name, column class, reading value (Aspect
valueOf(Item) ), writing value (
setValue(Item item, Aspect aspect) ), cell renderer (
getRenderer(Item) ), cell "editability" (
isCellEditable(Item) ), cell editor (
getEditor(Item) ), etc.
There are a lot of predefined column infos, so you'll probably never create a new one.
First, if a collection child is a
GenericDomValue, it's usually convenient to edit it directly in the table. For this, you may need one of the following classes:
BooleanColumnInfo, or more generic
GenericValueColumnInfo. But such collections are encountered very rarely.
A more common case is when a collection element is more complex and has several
GenericDomValue children. Then one may create a column for each of those children. The appropriate column info is
ChildGenericValueColumnInfo<T>. It will ask you for a
DomFixedChildDescription (one more thing from DOM reflection), a renderer and an editor — nothing else. So, the main things left to customize are the renderer and the editor.
As for the renderer, there are two main choices:
DefaultTableCellRenderer, and IntelliJ Platform's
BooleanTableCellRenderer. Editors are more complicated, but they closely resemble simple DOM controls.
DomUIFactory.createCellEditor() will create any of them automatically (including the editor for
PsiClass ), so that you won't need to think about which one to select every time.
Collection control is a complex control, so it's bound to a complex Swing component. It's called
DomTableView. It has a toolbar (you can override
DomTableView.getToolbarPosition() to customize its location), with Add and Delete buttons. If you want, you may specify custom addition actions in
DomCollectionControl.createAdditionActions() (it's recommended to extend
ControlAddAction ). If there is only one addition action, it will be invoked after pressing the Add button; if there are many, then a popup menu will be displayed. To change the removal policy, override the
The toolbar may also have an Edit button, if you specify that
DomCollectionControl.isEditable(). To add a behavior to this button, override
DomCollectionControl.doEdit(T). There can also be a Help button, if you pass a non-null String helpId parameter while constructing your
If there are no items in the collection,
DomTableView may display a special text (
DomTableView.getEmptyPaneText() ), instead of an empty table.
You can add your own popup menu to the control. Call the
DomTableView.installPopup() method after construction, and pass a
DefaultActionGroup with your popup actions.
Tables can have single or multiple (default) row selection. If you want to change this behavior, override
The easiest way to create a DOM-based UI form is to extend the
BasicDomElementComponent class. This will require you to pass some DOM element to the constructor. Then you bind an IntelliJ IDEA GUI Designer form to your subclass and design a beautiful form there. You will surely want to bind some controls to DOM UI, in which case you should of course ensure that they have right types. Finally, you should create some DOM controls in class' constructor and bind them. But you can create controls and bind them to the
DomElement 's children —
GenericDomValue 's automatically.
Just name your components properly and call the
bindProperties() method in the constructor. The field names should correspond to the getter names for the element's children. They may also be prefixed with "my". Imagine that you have such DOM interface:
In this case, the UI form class can look like this:
All the fields here are now bound to controls in a GUI form.
Very often you'll have to create your own file editor. Then, to use all the binding and undo functionality, it's suggested to inherit your
PerspectiveFileEditorProvider, create an instance of
DomFileEditor there, and pass a
BasicDomElementComponent. To easily create an editor with a caption at the top, like in our EJB and JSF, you may use the static method
DomFileEditor automatically listens to all changes in the document corresponding to the given DOM element, and therefore refreshes your component on undo. If you want to listen to changes in additional documents, use the methods
Thank you for your time and attention. We hope you've found this article really useful. You are welcome to post your questions and comments to our Open API and Plugin Development Forum.
The following bundled open-source plugins make (heavy) use of DOM: