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| <title>Manipulating Java code</title> |
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| <BODY> |
| <h2>Manipulating Java code</h2> |
| <P> |
| Your plug-in can use the JDT API to create classes or interfaces, add methods to existing types, or alter the methods for types. </P> |
| <P> |
| The simplest way to alter Java objects is to use the Java element API. More general techniques can be used to work with the raw source code for a Java element.</P> |
| |
| <H3> |
| Code modification using Java elements</h3> |
| |
| <H4> |
| Generating a compilation unit |
| </h4> |
| <P> |
| The easiest way to programmatically generate a compilation unit is to use |
| <b><a href="../reference/api/org/eclipse/jdt/core/IPackageFragment.html#createCompilationUnit(java.lang.String, java.lang.String, boolean, org.eclipse.core.runtime.IProgressMonitor)">IPackageFragment.createCompilationUnit</a></b>. |
| You specify the name and contents of the compilation unit. The compilation unit is created inside the package and the new |
| <b><a href="../reference/api/org/eclipse/jdt/core/ICompilationUnit.html"> ICompilationUnit</a></b> is returned. </P> |
| <P> |
| A compilation unit can be created generically by creating a file resource whose extension is "<b>.java"</b> in the appropriate folder that corresponds to the package directory. Using the generic resource API is a back door to the Java tooling, so the Java model is not updated until the generic resource change listeners are |
| notified and the JDT listeners update the Java model with the new compilation unit.</P> |
| |
| |
| <H4> |
| Modifying a compilation unit |
| </h4> |
| <P> |
| Most simple modifications of Java source can be done using the Java element API.</P> |
| <P> |
| For example, you can query a type from a compilation unit. Once you have the <a href="../reference/api/org/eclipse/jdt/core/IType.html"><b>IType</b></a>, you can use protocols such as |
| <a href="../reference/api/org/eclipse/jdt/core/IType.html#createField(java.lang.String, org.eclipse.jdt.core.IJavaElement, boolean, org.eclipse.core.runtime.IProgressMonitor)"><b>createField</b></a>, |
| <a href="../reference/api/org/eclipse/jdt/core/IType.html#createInitializer(java.lang.String, org.eclipse.jdt.core.IJavaElement, org.eclipse.core.runtime.IProgressMonitor)"><b>createInitializer</b></a>, |
| <a href="../reference/api/org/eclipse/jdt/core/IType.html#createMethod(java.lang.String, org.eclipse.jdt.core.IJavaElement, boolean, org.eclipse.core.runtime.IProgressMonitor)"><b>createMethod</b></a>, |
| or <a href="../reference/api/org/eclipse/jdt/core/IType.html#createType(java.lang.String, org.eclipse.jdt.core.IJavaElement, boolean, org.eclipse.core.runtime.IProgressMonitor)"><b>createType</b></a> |
| to add source code members to the type. The source code and information about the location of the member is supplied in these methods.</P> |
| <P> |
| The <b><a href="../reference/api/org/eclipse/jdt/core/ISourceManipulation.html"> ISourceManipulation</a></b> interface defines common source manipulations for Java elements. This includes methods for renaming, moving, copying, or deleting a type's member. </P> |
| |
| |
| <H4> |
| Working copies |
| </h4> |
| <P> |
| Code can be modified by manipulating the compilation unit (and thus the underlying |
| <a HREF="../../org.eclipse.platform.doc.isv/reference/api/org/eclipse/core/resources/IFile.html"><b>IFile</b></a> is modified) or |
| one can modify an in-memory copy of the compilation unit called a working copy. </P> |
| <P> |
| A working copy is obtained from a compilation unit using the |
| <b><a href="../reference/api/org/eclipse/jdt/core/ICompilationUnit.html#getWorkingCopy(org.eclipse.core.runtime.IProgressMonitor)">getWorkingCopy</a></b> |
| method. (Note that the compilation unit does not need to exist in the Java model |
| in order for a working copy to be created.) Whoever creates such a working copy is responsible for discarding it when not needed any longer using the |
| <b><a href="../reference/api/org/eclipse/jdt/core/ICompilationUnit.html#discardWorkingCopy()">discardWorkingCopy</a></b> |
| method. </P> |
| <P> |
| Working copies modify an in-memory buffer. The <b>getWorkingCopy()</b> method creates a default buffer, but |
| clients can provide their own buffer implementation using the |
| <b><a href="../reference/api/org/eclipse/jdt/core/ITypeRoot.html#getWorkingCopy(org.eclipse.jdt.core.WorkingCopyOwner, org.eclipse.core.runtime.IProgressMonitor)">getWorkingCopy(WorkingCopyOwner, IProgressMonitor)</a></b> |
| method. Clients can manipulate the text of this buffer directly. If they do so, they must synchronize the working copy with |
| the buffer from time to time using either the |
| <b><a href="../reference/api/org/eclipse/jdt/core/ICompilationUnit.html#reconcile(int, boolean, org.eclipse.jdt.core.WorkingCopyOwner, org.eclipse.core.runtime.IProgressMonitor)">reconcile(int, boolean, WorkingCopyOwner, IProgressMonitor)</a></b> |
| method. </P> |
| <P> |
| Finally a working copy can be saved to disk (replacing the original compilation unit) using the |
| <b><a href="../reference/api/org/eclipse/jdt/core/ICompilationUnit.html#commitWorkingCopy(boolean, org.eclipse.core.runtime.IProgressMonitor)">commitWorkingCopy</a></b> |
| method. </P> |
| <P> |
| For example the following code snippet creates a working copy on a compilation unit using a custom working copy owner. The snippet |
| modifies the buffer, reconciles the changes, commits the changes to disk and finally discards the working copy. </P> |
| <font color='#4444CC'><pre> |
| // Get original compilation unit |
| ICompilationUnit originalUnit = ...; |
| |
| // Get working copy owner |
| WorkingCopyOwner owner = ...; |
| |
| // Create working copy |
| ICompilationUnit workingCopy = originalUnit.getWorkingCopy(owner, null); |
| |
| // Modify buffer and reconcile |
| IBuffer buffer = ((IOpenable)workingCopy).getBuffer(); |
| buffer.append("class X {}"); |
| workingCopy.reconcile(ICompilationUnit.NO_AST, false, null, null); |
| |
| // Commit changes |
| workingCopy.commitWorkingCopy(false, null); |
| |
| // Destroy working copy |
| workingCopy.discardWorkingCopy(); |
| </pre></font> |
| <P> |
| Working copies can also be shared by several clients using a working copy owner. A working copy can be later retrieved using the |
| <b><a href="../reference/api/org/eclipse/jdt/core/ICompilationUnit.html#findWorkingCopy(org.eclipse.jdt.core.WorkingCopyOwner)">findWorkingCopy</a></b> |
| method. A shared working copy is thus keyed on the original compilation unit and on a working copy owner.</P> |
| <P> |
| The following shows how client 1 creates a shared working copy, client 2 retrieves this working copy, client 1 discards the |
| working copy, and client 2 trying to retrieve the shared working copy notices it does not exist any longer: </P> |
| <font color='#4444CC'><pre> |
| // Client 1 & 2: Get original compilation unit |
| ICompilationUnit originalUnit = ...; |
| |
| // Client 1 & 2: Get working copy owner |
| WorkingCopyOwner owner = ...; |
| |
| // Client 1: Create shared working copy |
| ICompilationUnit workingCopyForClient1 = originalUnit.getWorkingCopy(owner, null); |
| |
| // Client 2: Retrieve shared working copy |
| ICompilationUnit workingCopyForClient2 = originalUnit.findWorkingCopy(owner); |
| |
| // This is the same working copy |
| assert workingCopyForClient1 == workingCopyForClient2; |
| |
| // Client 1: Discard shared working copy |
| workingCopyForClient1.discardWorkingCopy(); |
| |
| // Client 2: Attempt to retrieve shared working copy and find out it's null |
| workingCopyForClient2 = originalUnit.findWorkingCopy(owner); |
| assert workingCopyForClient2 == null; |
| </pre></font> |
| |
| <H3>Code modification using the DOM/AST API</h3> |
| |
| |
| There are three ways to create a <b><a href="../reference/api/org/eclipse/jdt/core/dom/CompilationUnit.html">CompilationUnit</a></b>. |
| The first one is to use <b><a href="../reference/api/org/eclipse/jdt/core/dom/ASTParser.html">ASTParser</a></b>. |
| The second is to use <b><a href="../reference/api/org/eclipse/jdt/core/ICompilationUnit.html#reconcile(int, boolean, org.eclipse.jdt.core.WorkingCopyOwner, org.eclipse.core.runtime.IProgressMonitor)">ICompilationUnit#reconcile(...)</a></b>. |
| The third is to start from scratch using the factory methods on <b><a href="../reference/api/org/eclipse/jdt/core/dom/AST.html">AST</a></b> (Abstract Syntax Tree). |
| |
| <h4> |
| Creating an AST from existing source code |
| </h4> |
| |
| An instance of <b><a href="../reference/api/org/eclipse/jdt/core/dom/ASTParser.html">ASTParser</a></b> must be created with <b><a href="../reference/api/org/eclipse/jdt/core/dom/ASTParser.html#newParser(int)">ASTParser.newParser(int)</a></b>.<br> |
| <br> |
| The source code is given to the <b><a href="../reference/api/org/eclipse/jdt/core/dom/ASTParser.html">ASTParser</a></b> with one of the following methods: |
| <ul> |
| <li><b><a href="../reference/api/org/eclipse/jdt/core/dom/ASTParser.html#setSource(char[])">setSource(char[])</a></b>: to create the AST from source code</li> |
| <li><b><a href="../reference/api/org/eclipse/jdt/core/dom/ASTParser.html#setSource(org.eclipse.jdt.core.IClassFile)">setSource(IClassFile)</a></b>: to create the AST from a classfile</li> |
| <li><b><a href="../reference/api/org/eclipse/jdt/core/dom/ASTParser.html#setSource(org.eclipse.jdt.core.ICompilationUnit)">setSource(ICompilationUnit)</a></b>: to create the AST from a compilation unit</li> |
| </ul> |
| |
| Then the AST is created by calling <b><a href="../reference/api/org/eclipse/jdt/core/dom/ASTParser.html#createAST(org.eclipse.core.runtime.IProgressMonitor)">createAST(IProgressMonitor)</a></b>.<br> |
| <br> |
| The result is an AST with correct source positions for each node. |
| The resolution of bindings has to be requested before the creation of the tree with <b><a href="../reference/api/org/eclipse/jdt/core/dom/ASTParser.html#setResolveBindings(boolean)">setResolveBindings(boolean)</a></b>. |
| Resolving the bindings is a costly operation and should be done only when necessary. |
| As soon as the tree has been modified, all positions and bindings are lost. |
| |
| <h4> |
| Creating an AST by reconciling a working copy |
| </h4> |
| If a working copy is not consistent (has been modified) then an AST can be created by calling the method <b><a href="../reference/api/org/eclipse/jdt/core/ICompilationUnit.html#reconcile(int, boolean, org.eclipse.jdt.core.WorkingCopyOwner, org.eclipse.core.runtime.IProgressMonitor)">reconcile(int, boolean, WorkingCopyOwner, IProgressMonitor)</a></b>. |
| To request AST creation, call the <b><a href="../reference/api/org/eclipse/jdt/core/ICompilationUnit.html#reconcile(int, boolean, org.eclipse.jdt.core.WorkingCopyOwner, org.eclipse.core.runtime.IProgressMonitor)">reconcile(...)</a></b> |
| method with <b><a href="../reference/api/org/eclipse/jdt/core/dom/AST.html#JLS3">AST.JLS3</a></b> as first parameter.<br> |
| <br> |
| Its bindings are computed only if the problem requestor is active, or if the problem detection is forced. |
| Resolving the bindings is a costly operation and should be done only when necessary. As soon as the tree has been modified, all positions and |
| bindings are lost. |
| |
| <h4> |
| From scratch |
| </h4> |
| <P>It is possible to create a <b><a href="../reference/api/org/eclipse/jdt/core/dom/CompilationUnit.html">CompilationUnit</a></b> from scratch using the factory methods on <b><a href="../reference/api/org/eclipse/jdt/core/dom/AST.html">AST</a></b>. |
| These method names start with <b>new...</b>. The following is an example that creates a <b>HelloWorld</b> class. |
| </P> |
| <P>The first snippet is the generated output: |
| <font color='#4444CC'><pre> |
| package example; |
| import java.util.*; |
| public class HelloWorld { |
| public static void main(String[] args) { |
| System.out.println("Hello" + " world"); |
| } |
| } |
| </pre></font></p> |
| <P>The following snippet is the corresponding code that generates the output. |
| <font color='#4444CC'><pre> |
| AST ast = AST.newAST(AST.JLS3); |
| CompilationUnit unit = ast.newCompilationUnit(); |
| PackageDeclaration packageDeclaration = ast.newPackageDeclaration(); |
| packageDeclaration.setName(ast.newSimpleName("example")); |
| unit.setPackage(packageDeclaration); |
| ImportDeclaration importDeclaration = ast.newImportDeclaration(); |
| QualifiedName name = |
| ast.newQualifiedName( |
| ast.newSimpleName("java"), |
| ast.newSimpleName("util")); |
| importDeclaration.setName(name); |
| importDeclaration.setOnDemand(true); |
| unit.imports().add(importDeclaration); |
| TypeDeclaration type = ast.newTypeDeclaration(); |
| type.setInterface(false); |
| type.modifiers().add(ast.newModifier(Modifier.ModifierKeyword.PUBLIC_KEYWORD)); |
| type.setName(ast.newSimpleName("HelloWorld")); |
| MethodDeclaration methodDeclaration = ast.newMethodDeclaration(); |
| methodDeclaration.setConstructor(false); |
| List modifiers = methodDeclaration.modifiers(); |
| modifiers.add(ast.newModifier(Modifier.ModifierKeyword.PUBLIC_KEYWORD)); |
| modifiers.add(ast.newModifier(Modifier.ModifierKeyword.STATIC_KEYWORD)); |
| methodDeclaration.setName(ast.newSimpleName("main")); |
| methodDeclaration.setReturnType2(ast.newPrimitiveType(PrimitiveType.VOID)); |
| SingleVariableDeclaration variableDeclaration = ast.newSingleVariableDeclaration(); |
| variableDeclaration.setType(ast.newArrayType(ast.newSimpleType(ast.newSimpleName("String")))); |
| variableDeclaration.setName(ast.newSimpleName("args")); |
| methodDeclaration.parameters().add(variableDeclaration); |
| org.eclipse.jdt.core.dom.Block block = ast.newBlock(); |
| MethodInvocation methodInvocation = ast.newMethodInvocation(); |
| name = |
| ast.newQualifiedName( |
| ast.newSimpleName("System"), |
| ast.newSimpleName("out")); |
| methodInvocation.setExpression(name); |
| methodInvocation.setName(ast.newSimpleName("println")); |
| InfixExpression infixExpression = ast.newInfixExpression(); |
| infixExpression.setOperator(InfixExpression.Operator.PLUS); |
| StringLiteral literal = ast.newStringLiteral(); |
| literal.setLiteralValue("Hello"); |
| infixExpression.setLeftOperand(literal); |
| literal = ast.newStringLiteral(); |
| literal.setLiteralValue(" world"); |
| infixExpression.setRightOperand(literal); |
| methodInvocation.arguments().add(infixExpression); |
| ExpressionStatement expressionStatement = ast.newExpressionStatement(methodInvocation); |
| block.statements().add(expressionStatement); |
| methodDeclaration.setBody(block); |
| type.bodyDeclarations().add(methodDeclaration); |
| unit.types().add(type); |
| </pre></font></p> |
| <h4>Retrieving extra positions</h4> |
| The DOM/AST node contains only a pair of positions (the starting position and the length of the node). This is not always |
| sufficient. In order to retrieve intermediate positions, the <b><a href="../reference/api/org/eclipse/jdt/core/compiler/IScanner.html">IScanner</a></b> API should be used. For example, |
| we have an <b><a href="../reference/api/org/eclipse/jdt/core/dom/InstanceofExpression.html">InstanceofExpression</a></b> for which we want to know the |
| positions of the <i>instanceof</i> operator. |
| We could write the following method to achieve this: |
| <font color='#4444CC'><pre> |
| private int[] getOperatorPosition(Expression expression, char[] source) { |
| if (expression instanceof InstanceofExpression) { |
| IScanner scanner = ToolFactory.createScanner(false, false, false, false); |
| scanner.setSource(source); |
| int start = expression.getStartPosition(); |
| int end = start + expression.getLength(); |
| scanner.resetTo(start, end); |
| int token; |
| try { |
| while ((token = scanner.getNextToken()) != ITerminalSymbols.TokenNameEOF) { |
| switch(token) { |
| case ITerminalSymbols.TokenNameinstanceof: |
| return new int[] {scanner.getCurrentTokenStartPosition(), scanner.getCurrentTokenEndPosition()}; |
| } |
| } |
| } catch (InvalidInputException e) { |
| } |
| } |
| return null; |
| } |
| </pre></font> |
| The <b><a href="../reference/api/org/eclipse/jdt/core/compiler/IScanner.html">IScanner</a></b> is used to divide the input source into tokens. |
| Each token has a specific value that is defined in the <b><a href="../reference/api/org/eclipse/jdt/core/compiler/ITerminalSymbols.html">ITerminalSymbols</a></b> interface. It is |
| fairly simple to iterate and retrieve the right token. We also recommend that you use the scanner if you want to find the |
| position of the <i>super</i> keyword in a |
| <b><a href="../reference/api/org/eclipse/jdt/core/dom/SuperMethodInvocation.html">SuperMethodInvocation</a></b>. |
| |
| <h4>Source code modifcations</h4> |
| |
| <P> |
| Some source code modifications are not provided via the Java element API. |
| A more general way to edit source code (such as changing the source code for existing elements) is accomplished using the compilation unit's raw source code and the rewrite API of the DOM/AST.</P> |
| <P> |
| To perform DOM/AST rewriting, there are two sets of API: the descriptive rewriting and the modifying rewriting. |
| </p> |
| <p> |
| The descriptive API does not modify the AST but use <b><a href="../reference/api/org/eclipse/jdt/core/dom/rewrite/ASTRewrite.html">ASTRewrite</a></b> API to generate the descriptions of modifications. |
| The AST rewriter collects descriptions of modifications to nodes and translates these descriptions into text edits that can then be applied to the original source. |
| |
| <font color='#4444CC'><pre> |
| // creation of a Document |
| ICompilationUnit cu = ... ; // content is "public class X {\n}" |
| String source = cu.getSource(); |
| Document document= new Document(source); |
| |
| // creation of DOM/AST from a ICompilationUnit |
| ASTParser parser = ASTParser.newParser(AST.JLS3); |
| parser.setSource(cu); |
| CompilationUnit astRoot = (CompilationUnit) parser.createAST(null); |
| |
| // creation of ASTRewrite |
| ASTRewrite rewrite = ASTRewrite.create(astRoot.getAST()); |
| |
| // description of the change |
| SimpleName oldName = ((TypeDeclaration)astRoot.types().get(0)).getName(); |
| SimpleName newName = astRoot.getAST().newSimpleName("Y"); |
| rewrite.replace(oldName, newName, null); |
| |
| // computation of the text edits |
| TextEdit edits = rewrite.rewriteAST(document, cu.getJavaProject().getOptions(true)); |
| |
| // computation of the new source code |
| edits.apply(document); |
| String newSource = document.get(); |
| |
| // update of the compilation unit |
| cu.getBuffer().setContents(newSource); |
| </pre></font></p> |
| |
| <p> |
| The modifying API allows to modify directly the AST:</P> |
| <ul> |
| <li>Request the recording of modifications (<b><a href="../reference/api/org/eclipse/jdt/core/dom/CompilationUnit.html#recordModifications()">CompilationUnit.recordModifications()</a></b>).</li> |
| <li>Perform the modifications on the AST Nodes.</li> |
| <li>And when the modifications are finished, generate text edits that can then be applied to the original source (<b><a href="../reference/api/org/eclipse/jdt/core/dom/CompilationUnit.html#rewrite(org.eclipse.jface.text.IDocument, java.util.Map)">CompilationUnit.rewrite(...)</a></b>).</li> |
| </ul> |
| <font color='#4444CC'><pre> |
| // creation of a Document |
| ICompilationUnit cu = ... ; // content is "public class X {\n}" |
| String source = cu.getSource(); |
| Document document= new Document(source); |
| |
| // creation of DOM/AST from a ICompilationUnit |
| ASTParser parser = ASTParser.newParser(AST.JLS3); |
| parser.setSource(cu); |
| CompilationUnit astRoot = (CompilationUnit) parser.createAST(null); |
| |
| // start record of the modifications |
| astRoot.recordModifications(); |
| |
| // modify the AST |
| TypeDeclaration typeDeclaration = (TypeDeclaration)astRoot.types().get(0); |
| SimpleName newName = astRoot.getAST().newSimpleName("Y"); |
| typeDeclaration.setName(newName); |
| |
| // computation of the text edits |
| TextEdit edits = astRoot.rewrite(document, cu.getJavaProject().getOptions(true)); |
| |
| // computation of the new source code |
| edits.apply(document); |
| String newSource = document.get(); |
| |
| // update of the compilation unit |
| cu.getBuffer().setContents(newSource); |
| </pre></font> |
| |
| <H3> |
| <a name="javadeltas"> |
| Responding to changes in Java elements</a></h3> |
| <P> |
| If your plug-in needs to know about changes to Java elements after the fact, you can register a Java |
| <a href="../reference/api/org/eclipse/jdt/core/IElementChangedListener.html"><b> IElementChangedListener</b></a> with |
| <a href="../reference/api/org/eclipse/jdt/core/JavaCore.html"><b>JavaCore</b></a>.</P> |
| <font color='#4444CC'><pre> |
| JavaCore.addElementChangedListener(new MyJavaElementChangeReporter()); |
| </pre></font> |
| <P> |
| You can be more specific and specify the type of events you're interested in using |
| <a href="../reference/api/org/eclipse/jdt/core/JavaCore.html#addElementChangedListener(org.eclipse.jdt.core.IElementChangedListener, int)"><b> addElementChangedListener(IElementChangedListener, int)</b></a>. </P> |
| <P> |
| For example, if you're only interested in listening for events during a reconcile operation: </P> |
| <font color='#4444CC'><pre> |
| JavaCore.addElementChangedListener(new MyJavaElementChangeReporter(), ElementChangedEvent.POST_RECONCILE); |
| </pre></font> |
| <P> |
| There are two kinds of events that are supported by <b>JavaCore</b>:</P> |
| <ul> |
| <li><a href="../reference/api/org/eclipse/jdt/core/ElementChangedEvent.html#POST_CHANGE"><b>POST_CHANGE</b></a>: |
| Listeners of this event kind will get notified during the corresponding |
| <a HREF="../../org.eclipse.platform.doc.isv/reference/api/org/eclipse/core/resources/IResourceChangeEvent.html#POST_CHANGE"><b>POST_CHANGE</b></a> |
| resource change notification.</li> |
| <li><a href="../reference/api/org/eclipse/jdt/core/ElementChangedEvent.html#POST_RECONCILE"><b>POST_RECONCILE</b></a>: |
| Listeners of this event kind will get notified at the end of a reconcile operation on a working copy |
| (see <a href="../reference/api/org/eclipse/jdt/core/ICompilationUnit.html#reconcile(int, boolean, org.eclipse.jdt.core.WorkingCopyOwner, org.eclipse.core.runtime.IProgressMonitor)"><b>ICompilationUnit.reconcile(int, boolean, WorkingCopyOwner, IProgressMonitor)</b></a>).</li> |
| </ul> |
| <P> |
| Java element change listeners are similar conceptually to resource change listeners |
| (described in |
| <a HREF="../../org.eclipse.platform.doc.isv/guide/resAdv_events.htm" CLASS="XRef">tracking resource changes</a>). The following snippet implements a Java element change reporter that prints the element deltas to the system console.</P> |
| <font color='#4444CC'><pre> |
| public class MyJavaElementChangeReporter implements IElementChangedListener { |
| public void elementChanged(ElementChangedEvent event) { |
| IJavaElementDelta delta= event.getDelta(); |
| if (delta != null) { |
| System.out.println("delta received: "); |
| System.out.print(delta); |
| } |
| } |
| } |
| </pre></font> |
| <P> |
| The <a href="../reference/api/org/eclipse/jdt/core/IJavaElementDelta.html"><b> IJavaElementDelta</b></a> includes the |
| <a href="../reference/api/org/eclipse/jdt/core/IJavaElementDelta.html#getElement()">element</a> that was |
| changed and <a href="../reference/api/org/eclipse/jdt/core/IJavaElementDelta.html#getFlags()">flags</a> describing |
| the kind of change that occurred. Most of the time the delta tree is rooted at the Java Model level. Clients must then navigate |
| this delta using <a href="../reference/api/org/eclipse/jdt/core/IJavaElementDelta.html#getAffectedChildren()"><b>getAffectedChildren</b></a> |
| to find out what projects have changed. </P> |
| <P> |
| The following example method traverses a delta and prints the elements that have been added, removed and changed:</P> |
| <font color='#4444CC'><pre> |
| void traverseAndPrint(IJavaElementDelta delta) { |
| switch (delta.getKind()) { |
| case IJavaElementDelta.ADDED: |
| System.out.println(delta.getElement() + " was added"); |
| break; |
| case IJavaElementDelta.REMOVED: |
| System.out.println(delta.getElement() + " was removed"); |
| break; |
| case IJavaElementDelta.CHANGED: |
| System.out.println(delta.getElement() + " was changed"); |
| if ((delta.getFlags() & IJavaElementDelta.F_CHILDREN) != 0) { |
| System.out.println("The change was in its children"); |
| } |
| if ((delta.getFlags() & IJavaElementDelta.F_CONTENT) != 0) { |
| System.out.println("The change was in its content"); |
| } |
| /* Others flags can also be checked */ |
| break; |
| } |
| IJavaElementDelta[] children = delta.getAffectedChildren(); |
| for (int i = 0; i < children.length; i++) { |
| traverseAndPrint(children[i]); |
| } |
| } |
| </pre></font> |
| |
| <P> |
| Several kinds of operations can trigger a Java element change notification. Here are some examples:</P> |
| <ul> |
| <li>Creating a resource, e.g. <a href="../reference/api/org/eclipse/jdt/core/IPackageFragment.html#createCompilationUnit(java.lang.String, java.lang.String, boolean, org.eclipse.core.runtime.IProgressMonitor)"><b>IPackageFragment.createCompilationUnit</b></a> |
| (the delta indicates the <a href="../reference/api/org/eclipse/jdt/core/IJavaElementDelta.html#ADDED">addition</a> of the compilation unit)</li> |
| <li>Modifying a resource, e.g. <a href="../reference/api/org/eclipse/jdt/core/ICompilationUnit.html#createType(java.lang.String, org.eclipse.jdt.core.IJavaElement, boolean, org.eclipse.core.runtime.IProgressMonitor)"><b>ICompilationUnit.createType</b></a> |
| (the delta indicates that the compilation unit has <a href="../reference/api/org/eclipse/jdt/core/IJavaElementDelta.html#CHANGED">changed</a> and that a type was |
| <a href="../reference/api/org/eclipse/jdt/core/IJavaElementDelta.html#getAddedChildren()"> added as a child</a> of this compilation unit)</li> |
| <li>Modifying a project's classpath, e.g. <a href="../reference/api/org/eclipse/jdt/core/IJavaProject.html#setRawClasspath(org.eclipse.jdt.core.IClasspathEntry[], org.eclipse.core.runtime.IProgressMonitor)"><b>IJavaProject.setRawClasspath</b></a> |
| (the delta indicates that package fragment roots have been <a href="../reference/api/org/eclipse/jdt/core/IJavaElementDelta.html#F_ADDED_TO_CLASSPATH">added to the classpath</a>, |
| <a href="../reference/api/org/eclipse/jdt/core/IJavaElementDelta.html#F_REMOVED_FROM_CLASSPATH">removed from the classpath</a>, or |
| <a href="../reference/api/org/eclipse/jdt/core/IJavaElementDelta.html#F_CLASSPATH_REORDER">reordered on the classpath</a>)</li> |
| <li>Modifying a classpath variable value, e.g. <a href="../reference/api/org/eclipse/jdt/core/JavaCore.html#setClasspathVariable(java.lang.String, org.eclipse.core.runtime.IPath, org.eclipse.core.runtime.IProgressMonitor)"><b>JavaCore.setClasspathVariable</b></a> |
| (the delta also indicates that package fragment roots have been affected)</li> |
| <li>Reconciling a working copy with its buffer, e.g. <a href="../reference/api/org/eclipse/jdt/core/ICompilationUnit.html#reconcile(int, boolean, org.eclipse.jdt.core.WorkingCopyOwner, org.eclipse.core.runtime.IProgressMonitor)"><b>ICompilationUnit.reconcile</b></a></li> |
| <li>Modifying an <a HREF="../../org.eclipse.platform.doc.isv/reference/api/org/eclipse/core/resources/IFile.html"><b>IFile</b></a> that ends with ".java" and that is on the |
| project's classpath, e.g. using <b>IFile.setContents</b> (the delta indicates that a compilation unit was changed, but |
| <a href="../reference/api/org/eclipse/jdt/core/IJavaElementDelta.html#F_FINE_GRAINED">no finer-grained information</a> |
| is provided as this was not done through a Java Model operation)</li> |
| </ul> |
| <P>Similar to <a HREF="../../org.eclipse.platform.doc.isv/reference/api/org/eclipse/core/resources/IResourceDelta.html"><b>IResourceDelta</b></a> |
| the Java element deltas can be batched using an |
| <a HREF="../../org.eclipse.platform.doc.isv/reference/api/org/eclipse/core/resources/IWorkspaceRunnable.html"><b>IWorkspaceRunnable</b></a>. |
| The deltas resulting from several Java Model operations that are run inside a <b>IWorkspaceRunnable</b> are merged and reported at once. </P> |
| <P><a href="../reference/api/org/eclipse/jdt/core/JavaCore.html"><b>JavaCore</b></a><b> |
| </b>provides a <b>run</b> method for batching Java element changes. </P> |
| <P> |
| For example, the following code fragment will trigger 2 Java element change events: </P> |
| <font color='#4444CC'><pre> |
| // Get package |
| IPackageFragment pkg = ...; |
| |
| // Create 2 compilation units |
| ICompilationUnit unitA = pkg.createCompilationUnit("A.java", "public class A {}", false, null); |
| ICompilationUnit unitB = pkg.createCompilationUnit("B.java", "public class B {}", false, null); |
| </pre></font> |
| <P> |
| Whereas the following code fragment will trigger 1 Java element change event: </P> |
| <font color='#4444CC'><pre> |
| // Get package |
| final IPackageFragment pkg = ...; |
| |
| // Create 2 compilation units |
| JavaCore.run( |
| new IWorkspaceRunnable() { |
| public void run(IProgressMonitor monitor) throws CoreException { |
| ICompilationUnit unitA = pkg.createCompilationUnit("A.java", "public class A {}", false, null); |
| ICompilationUnit unitB = pkg.createCompilationUnit("B.java", "public class B {}", false, null); |
| } |
| }, |
| null); |
| </pre></font> |
| |
| |
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