Package org.eclipse.jdt.core.eval

Interface IEvaluationContext

public interface IEvaluationContext
An evaluation context supports evaluating code snippets.

A code snippet is pretty much any valid piece of Java code that could be pasted into the body of a method and compiled. However, there are two areas where the rules are slightly more liberal.

First, a code snippet can return heterogeneous types. Inside the same code snippet an int could be returned on one line, and a String on the next, etc. For example, the following would be considered a valid code snippet: 

 
 char c = '3';
 switch (c) {
   case '1': return 1;
   case '2': return '2';
   case '3': return "3";
   default: return null;
 }

Second, if the last statement is only an expression, the return keyword is implied. For example, the following returns false: 

 
 int i = 1;
 i == 2

Global variables are an additional feature of evaluation contexts. Within an evaluation context, global variables maintain their value across evaluations. These variables are particularly useful for storing the result of an evaluation for use in subsequent evaluations.

The evaluation context remembers the name of the package in which code snippets are run. The user can set this to any package, thereby gaining access to types that are normally only visible within that package.

Finally, the evaluation context remembers a list of import declarations. The user can import any packages and types so that the code snippets may refer to types by their shorter simple names.

Example of use: 

 
 IJavaProject project = getJavaProject();
 IEvaluationContext context = project.newEvaluationContext();
 String codeSnippet = "int i= 0; i++";
 ICodeSnippetRequestor requestor = ...;
 context.evaluateCodeSnippet(codeSnippet, requestor, progressMonitor);

IJavaProject.newEvaluationContext can be used to obtain an instance.

See Also:
Restriction:
This interface is not intended to be implemented by clients.

  • Method Details

    • allVariables

      IGlobalVariable[] allVariables()
      Returns the global variables declared in this evaluation context. The variables are maintained in the order they are created in.
      Returns:
      the list of global variables

    • codeComplete

      void codeComplete(String codeSnippet, int position, ICompletionRequestor requestor) throws JavaModelException
      Deprecated.
      Use codeComplete(String,int,CompletionRequestor) instead.
      Performs a code completion at the given position in the given code snippet, reporting results to the given completion requestor.

      Note that code completion does not involve evaluation.

      Parameters:
      codeSnippet - the code snippet to complete in
      position - the character position in the code snippet to complete at, or -1 indicating the beginning of the snippet
      requestor - the code completion requestor capable of accepting all possible types of completions
      Throws:
      JavaModelException - if code completion could not be performed. Reasons include:
      • The position specified is less than -1 or is greater than the snippet's length (INDEX_OUT_OF_BOUNDS)
      Since:
      2.0

    • codeComplete

      void codeComplete(String codeSnippet, int position, ICompletionRequestor requestor, WorkingCopyOwner owner) throws JavaModelException
      Deprecated.
      Use codeComplete(String,int,CompletionRequestor,WorkingCopyOwner) instead.
      Performs a code completion at the given position in the given code snippet, reporting results to the given completion requestor. It considers types in the working copies with the given owner first. In other words, the owner's working copies will take precedence over their original compilation units in the workspace.

      Note that if a working copy is empty, it will be as if the original compilation unit had been deleted.

      Note that code completion does not involve evaluation.

      Parameters:
      codeSnippet - the code snippet to complete in
      position - the character position in the code snippet to complete at, or -1 indicating the beginning of the snippet
      requestor - the code completion requestor capable of accepting all possible types of completions
      owner - the owner of working copies that take precedence over their original compilation units
      Throws:
      JavaModelException - if code completion could not be performed. Reasons include:
      • The position specified is less than -1 or is greater than the snippet's length (INDEX_OUT_OF_BOUNDS)
      Since:
      3.0

    • codeComplete

      void codeComplete(String codeSnippet, int position, CompletionRequestor requestor) throws JavaModelException
      Performs a code completion at the given position in the given code snippet, reporting results to the given completion requestor.

      Note that code completion does not involve evaluation.

      Parameters:
      codeSnippet - the code snippet to complete in
      position - the character position in the code snippet to complete at, or -1 indicating the beginning of the snippet
      requestor - the code completion requestor capable of accepting all possible types of completions
      Throws:
      JavaModelException - if code completion could not be performed. Reasons include:
      • The position specified is less than -1 or is greater than the snippet's length (INDEX_OUT_OF_BOUNDS)
      Since:
      3.1

    • codeComplete

      void codeComplete(String codeSnippet, int position, CompletionRequestor requestor, org.eclipse.core.runtime.IProgressMonitor monitor) throws JavaModelException
      Performs a code completion at the given position in the given code snippet, reporting results to the given completion requestor.

      Note that code completion does not involve evaluation.

      If IProgressMonitor is not null then some proposals which can be very long to compute are proposed. To avoid that the code assist operation take too much time a IProgressMonitor which automatically cancel the code assist operation when a specified amount of time is reached could be used. 

      
 new IProgressMonitor() {
     private final static int TIMEOUT = 500; //ms
     private long endTime;
     public void beginTask(String name, int totalWork) {
         fEndTime= System.currentTimeMillis() + TIMEOUT;
     }
     public boolean isCanceled() {
         return endTime <= System.currentTimeMillis();
     }
     ...
 };
      Parameters:
      codeSnippet - the code snippet to complete in
      position - the character position in the code snippet to complete at, or -1 indicating the beginning of the snippet
      requestor - the code completion requestor capable of accepting all possible types of completions
      monitor - the progress monitor used to report progress
      Throws:
      JavaModelException - if code completion could not be performed. Reasons include:
      • The position specified is less than -1 or is greater than the snippet's length (INDEX_OUT_OF_BOUNDS)
      Since:
      3.5

    • codeComplete

      void codeComplete(String codeSnippet, int position, CompletionRequestor requestor, WorkingCopyOwner owner) throws JavaModelException
      Performs a code completion at the given position in the given code snippet, reporting results to the given completion requestor. It considers types in the working copies with the given owner first. In other words, the owner's working copies will take precedence over their original compilation units in the workspace.

      Note that if a working copy is empty, it will be as if the original compilation unit had been deleted.

      Note that code completion does not involve evaluation.

      Parameters:
      codeSnippet - the code snippet to complete in
      position - the character position in the code snippet to complete at, or -1 indicating the beginning of the snippet
      requestor - the code completion requestor capable of accepting all possible types of completions
      owner - the owner of working copies that take precedence over their original compilation units
      Throws:
      JavaModelException - if code completion could not be performed. Reasons include:
      • The position specified is less than -1 or is greater than the snippet's length (INDEX_OUT_OF_BOUNDS)
      Since:
      3.1

    • codeComplete

      void codeComplete(String codeSnippet, int position, CompletionRequestor requestor, WorkingCopyOwner owner, org.eclipse.core.runtime.IProgressMonitor monitor) throws JavaModelException
      Performs a code completion at the given position in the given code snippet, reporting results to the given completion requestor. It considers types in the working copies with the given owner first. In other words, the owner's working copies will take precedence over their original compilation units in the workspace.

      Note that if a working copy is empty, it will be as if the original compilation unit had been deleted.

      Note that code completion does not involve evaluation.

      If IProgressMonitor is not null then some proposals which can be very long to compute are proposed. To avoid that the code assist operation take too much time a IProgressMonitor which automatically cancel the code assist operation when a specified amount of time is reached could be used. 

      
 new IProgressMonitor() {
     private final static int TIMEOUT = 500; //ms
     private long endTime;
     public void beginTask(String name, int totalWork) {
         fEndTime= System.currentTimeMillis() + TIMEOUT;
     }
     public boolean isCanceled() {
         return endTime <= System.currentTimeMillis();
     }
     ...
 };
      Parameters:
      codeSnippet - the code snippet to complete in
      position - the character position in the code snippet to complete at, or -1 indicating the beginning of the snippet
      requestor - the code completion requestor capable of accepting all possible types of completions
      owner - the owner of working copies that take precedence over their original compilation units
      monitor - the progress monitor used to report progress
      Throws:
      JavaModelException - if code completion could not be performed. Reasons include:
      • The position specified is less than -1 or is greater than the snippet's length (INDEX_OUT_OF_BOUNDS)
      Since:
      3.5

    • codeSelect

      IJavaElement[] codeSelect(String codeSnippet, int offset, int length) throws JavaModelException
      Resolves and returns a collection of Java elements corresponding to the source code at the given positions in the given code snippet.

      Note that code select does not involve evaluation, and problems are never reported.

      Parameters:
      codeSnippet - the code snippet to resolve in
      offset - the position in the code snippet of the first character of the code to resolve
      length - the length of the selected code to resolve
      Returns:
      the (possibly empty) list of selection Java elements
      Throws:
      JavaModelException - if code resolve could not be performed. Reasons include:
      • The position specified is less than -1 or is greater than the snippet's length (INDEX_OUT_OF_BOUNDS)

    • codeSelect

      IJavaElement[] codeSelect(String codeSnippet, int offset, int length, WorkingCopyOwner owner) throws JavaModelException
      Resolves and returns a collection of Java elements corresponding to the source code at the given positions in the given code snippet. It considers types in the working copies with the given owner first. In other words, the owner's working copies will take precedence over their original compilation units in the workspace.

      Note that if a working copy is empty, it will be as if the original compilation unit had been deleted.

      Note that code select does not involve evaluation, and problems are never reported.

      Parameters:
      codeSnippet - the code snippet to resolve in
      offset - the position in the code snippet of the first character of the code to resolve
      length - the length of the selected code to resolve
      owner - the owner of working copies that take precedence over their original compilation units
      Returns:
      the (possibly empty) list of selection Java elements
      Throws:
      JavaModelException - if code resolve could not be performed. Reasons include:
      • The position specified is less than -1 or is greater than the snippet's length (INDEX_OUT_OF_BOUNDS)
      Since:
      3.0

    • deleteVariable

      void deleteVariable(IGlobalVariable variable)
      Deletes the given variable from this evaluation context. Does nothing if the given variable has already been deleted.
      Parameters:
      variable - the global variable

    • evaluateCodeSnippet

      void evaluateCodeSnippet(String codeSnippet, String[] localVariableTypeNames, String[] localVariableNames, int[] localVariableModifiers, IType declaringType, boolean isStatic, boolean isConstructorCall, ICodeSnippetRequestor requestor, org.eclipse.core.runtime.IProgressMonitor progressMonitor) throws JavaModelException
      Evaluates the given code snippet in the context of a suspended thread. The code snippet is compiled along with this context's package declaration, imports, and global variables. The given requestor's acceptProblem method is called for each compilation problem that is detected. Then the resulting class files are handed to the given requestor's acceptClassFiles method to deploy and run.

      The requestor is expected to:

      1. send the class files to the target VM,
      2. load them (starting with the code snippet class),
      3. create a new instance of the code snippet class,
      4. run the method run() of the code snippet,
      5. retrieve the values of the local variables,
      6. retrieve the returned value of the code snippet

      This method is long-running; progress and cancellation are provided by the given progress monitor.

      Parameters:
      codeSnippet - the code snippet
      localVariableTypeNames - the dot-separated fully qualified names of the types of the local variables.
      localVariableNames - the names of the local variables as they are declared in the user's code.
      localVariableModifiers - the modifiers of the local variables (default modifier or final modifier).
      declaringType - the type in which the code snippet is evaluated.
      isStatic - whether the code snippet is evaluated in a static member of the declaring type.
      isConstructorCall - whether the code snippet is evaluated in a constructor of the declaring type.
      requestor - the code snippet requestor
      progressMonitor - a progress monitor
      Throws:
      JavaModelException - if a runtime problem occurred or if this context's project has no build state

    • evaluateCodeSnippet

      void evaluateCodeSnippet(String codeSnippet, ICodeSnippetRequestor requestor, org.eclipse.core.runtime.IProgressMonitor progressMonitor) throws JavaModelException
      Evaluates the given code snippet. The code snippet is compiled along with this context's package declaration, imports, and global variables. The given requestor's acceptProblem method is called for each compilation problem that is detected. Then the resulting class files are handed to the given requestor's acceptClassFiles method to deploy and run. The requestor is also responsible for getting the result back.

      This method is long-running; progress and cancellation are provided by the given progress monitor.

      Parameters:
      codeSnippet - the code snippet
      requestor - the code snippet requestor
      progressMonitor - a progress monitor
      Throws:
      JavaModelException - if a runtime problem occurred or if this context's project has no build state

    • evaluateVariable

      void evaluateVariable(IGlobalVariable variable, ICodeSnippetRequestor requestor, org.eclipse.core.runtime.IProgressMonitor progressMonitor) throws JavaModelException
      Evaluates the given global variable. During this operation, this context's package declaration, imports, and all its declared variables are verified. The given requestor's acceptProblem method will be called for each problem that is detected.

      This method is long-running; progress and cancellation are provided by the given progress monitor.

      Parameters:
      variable - the global variable
      requestor - the code snippet requestor
      progressMonitor - a progress monitor
      Throws:
      JavaModelException - if a runtime problem occurred or if this context's project has no build state

    • getImports

      String[] getImports()
      Returns the import declarations for this evaluation context. Returns and empty list if there are no imports (the default if the imports have never been set). The syntax for the import corresponds to a fully qualified type name, or to an on-demand package name as defined by ImportDeclaration (JLS2 7.5). For example, "java.util.Hashtable" or "java.util.*".
      Returns:
      the list of import names

    • getPackageName

      String getPackageName()
      Returns the name of the package in which code snippets are to be compiled and run. Returns an empty string for the default package (the default if the package name has never been set). For example, "com.example.myapp".
      Returns:
      the dot-separated package name, or the empty string indicating the default package

    • getProject

      IJavaProject getProject()
      Returns the Java project this evaluation context was created for.
      Returns:
      the Java project

    • newVariable

      IGlobalVariable newVariable(String typeName, String name, String initializer)
      Creates a new global variable with the given name, type, and initializer.

      The typeName and initializer are interpreted in the context of this context's package and import declarations.

      The syntax for a type name corresponds to Type in Field Declaration (JLS2 8.3).

      Parameters:
      typeName - the type name
      name - the name of the global variable
      initializer - the initializer expression, or null if the variable is not initialized
      Returns:
      a new global variable with the given name, type, and initializer

    • setImports

      void setImports(String[] imports)
      Sets the import declarations for this evaluation context. An empty list indicates there are no imports. The syntax for the import corresponds to a fully qualified type name, or to an on-demand package name as defined by ImportDeclaration (JLS2 7.5). For example, "java.util.Hashtable" or "java.util.*".
      Parameters:
      imports - the list of import names

    • setPackageName

      void setPackageName(String packageName)
      Sets the dot-separated name of the package in which code snippets are to be compiled and run. For example, "com.example.myapp".
      Parameters:
      packageName - the dot-separated package name, or the empty string indicating the default package

    • validateImports

      void validateImports(ICodeSnippetRequestor requestor) throws JavaModelException
      Validates this evaluation context's import declarations. The given requestor's acceptProblem method is called for each problem that is detected.
      Parameters:
      requestor - the code snippet requestor
      Throws:
      JavaModelException - if this context's project has no build state

    • codeComplete

      void codeComplete(String codeSnippet, int position, ICodeCompletionRequestor requestor) throws JavaModelException
      Deprecated.
      - use codeComplete(String, int, ICompletionRequestor) instead
      Performs a code completion at the given position in the given code snippet, reporting results to the given completion requestor.

      Note that code completion does not involve evaluation.

      Parameters:
      codeSnippet - the code snippet to complete in
      position - the character position in the code snippet to complete at, or -1 indicating the beginning of the snippet
      requestor - the code completion requestor capable of accepting all possible types of completions
      Throws:
      JavaModelException - if code completion could not be performed. Reasons include:
      • The position specified is less than -1 or is greater than the snippet's length (INDEX_OUT_OF_BOUNDS)