Class JELUtils

java.lang.Object
uk.ac.starlink.ttools.jel.JELUtils

public class JELUtils extends Object
This class provides some utility methods for use with the JEL expression compiler.
Since:
11 Feb 2005
Author:
Mark Taylor (Starlink)
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final String
    System property name for adding colon-separated list of additional classnames containing static methods.
  • Constructor Summary

    Constructors
    Constructor
    Description
     
  • Method Summary

    Modifier and Type
    Method
    Description
    static void
    checkExpressionType(gnu.jel.Library lib, uk.ac.starlink.table.StarTable table, String expr, Class<?> clazz)
    Checks that an expression is legal and returns a particular class.
    static gnu.jel.CompiledExpression
    compile(gnu.jel.Library lib, uk.ac.starlink.table.StarTable table, String expr)
    Compiles an expression in the context of a given table.
    static gnu.jel.CompiledExpression
    compile(gnu.jel.Library lib, uk.ac.starlink.table.StarTable table, String expr, Class<?> clazz)
    Compiles an expression in the context of a given table with a required type for the result.
    static gnu.jel.CompiledExpression[]
    Compiles a set of expressions relating to a table.
    compileQuantity(gnu.jel.Library lib, StarTableJELRowReader jelRdr, String expr, Class<?> clazz)
    Compiles an expression in the context of a table reader to give a JELQuantity.
    static Function<gnu.jel.Library,gnu.jel.CompiledExpression>
    compiler(uk.ac.starlink.table.StarTable table, String expr, Class<?> clazz)
    Returns a function that can compile a fixed expression from a Library.
    createDatalessRowReader(uk.ac.starlink.table.StarTable table)
    Returns a row reader that can be used for expression evaluation, optionally in the context of the non-data parts of a given context table.
    static gnu.jel.Library
    createLibrary(Class<?>[] staticLib, Class<?>[] dynamicLib, gnu.jel.DVMap resolver)
    Creates a JEL Library from basic information.
    static Class<?>
    getExpressionType(gnu.jel.Library lib, uk.ac.starlink.table.StarTable table, String expr)
    Gives the return type of an expression.
    static gnu.jel.Library
    Returns a JEL Library suitable for expression evaluation within a table.
    static List<Class<?>>
    Returns the list of classes whose static methods will be mapped into the JEL evaluation namespace.
    static Class<?>
    Returns a non-primitive version of a given class.
    toIOException(gnu.jel.CompilationException e, String expr)
    Utility method to convert a CompilationException into an IOException.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Field Details

    • CLASSES_PROPERTY

      public static final String CLASSES_PROPERTY
      System property name for adding colon-separated list of additional classnames containing static methods.
      See Also:
  • Constructor Details

    • JELUtils

      public JELUtils()
  • Method Details

    • getLibrary

      public static gnu.jel.Library getLibrary(JELRowReader reader)
      Returns a JEL Library suitable for expression evaluation within a table.
      Parameters:
      reader - object which can read rows from the table to be used for expression evaluation; may be null if there are no references to table-related expressions
      Returns:
      a JEL library
    • createLibrary

      public static gnu.jel.Library createLibrary(Class<?>[] staticLib, Class<?>[] dynamicLib, gnu.jel.DVMap resolver)
      Creates a JEL Library from basic information. This method should generally be used rather than the Library constructor, since it may apply additional customisation. Currently, it fixes static methods marked with the StateDependent annotation appropriately.
      Parameters:
      staticLib - array of classes whose public static methods are exported
      dynamicLib - array of classes whose public methods are exported
      resolver - object used to resolve names
      Returns:
      new library
      See Also:
      • Library(java.lang.Class<?>[], java.lang.Class<?>[], java.lang.Class<?>[], gnu.jel.DVMap, java.util.HashMap<java.lang.String, java.lang.Class<?>>)
    • createDatalessRowReader

      public static JELRowReader createDatalessRowReader(uk.ac.starlink.table.StarTable table)
      Returns a row reader that can be used for expression evaluation, optionally in the context of the non-data parts of a given context table. If the table is non-null, things like its parameters and row counts are available for reference. If the table is null, those things won't be available. In any case, references to table columns will not be recognised.
      Parameters:
      table - context table, or null
      Returns:
      row reader
    • getStaticClasses

      public static List<Class<?>> getStaticClasses()
      Returns the list of classes whose static methods will be mapped into the JEL evaluation namespace. This may be modified.
      Returns:
      list of classes with static methods
    • getExpressionType

      public static Class<?> getExpressionType(gnu.jel.Library lib, uk.ac.starlink.table.StarTable table, String expr) throws gnu.jel.CompilationException
      Gives the return type of an expression. This also has the effect of testing that an expression is legal.
      Parameters:
      lib - JEL library
      table - context table
      expr - string representation of the expression
      Returns:
      class which evaluation of expr using lib will return
      Throws:
      gnu.jel.CompilationException - if expr cannot be compiled
    • checkExpressionType

      public static void checkExpressionType(gnu.jel.Library lib, uk.ac.starlink.table.StarTable table, String expr, Class<?> clazz) throws gnu.jel.CompilationException
      Checks that an expression is legal and returns a particular class.
      Parameters:
      lib - JEL library
      table - context table
      expr - string representation of the expression
      clazz - return type required from expr
      Throws:
      gnu.jel.CompilationException - if expr cannot be compiled or will return a type other than clazz (or one of its subtypes)
    • compile

      public static gnu.jel.CompiledExpression compile(gnu.jel.Library lib, uk.ac.starlink.table.StarTable table, String expr, Class<?> clazz) throws gnu.jel.CompilationException
      Compiles an expression in the context of a given table with a required type for the result. Additional to the behaviour of Evaluator.compile this also checks for expressions which exactly match table column names, even if they are not syntactically legal identifiers.
      Parameters:
      lib - JEL library
      table - context table
      expr - expression string
      clazz - required class of resulting expression
      Returns:
      compiled expression
      Throws:
      gnu.jel.CompilationException
    • compile

      public static gnu.jel.CompiledExpression compile(gnu.jel.Library lib, uk.ac.starlink.table.StarTable table, String expr) throws gnu.jel.CompilationException
      Compiles an expression in the context of a given table. Additional to the behaviour of Evaluator.compile this also checks for expressions which exactly match table column names, even if they are not syntactically legal identifiers.
      Parameters:
      lib - JEL library
      table - context table
      expr - expression string
      Returns:
      compiled expression
      Throws:
      gnu.jel.CompilationException
    • compileQuantity

      public static JELQuantity compileQuantity(gnu.jel.Library lib, StarTableJELRowReader jelRdr, String expr, Class<?> clazz) throws gnu.jel.CompilationException
      Compiles an expression in the context of a table reader to give a JELQuantity. This does the same job as the compile methods, but it provides additional metadata if it can be retrieved from the table context.
      Parameters:
      lib - JEL library
      jelRdr - context table reader
      expr - expression string
      clazz - required return type of compiled expression, or null if no requirement
      Returns:
      compiled quantity
      Throws:
      gnu.jel.CompilationException
    • compiler

      public static Function<gnu.jel.Library,gnu.jel.CompiledExpression> compiler(uk.ac.starlink.table.StarTable table, String expr, Class<?> clazz) throws gnu.jel.CompilationException
      Returns a function that can compile a fixed expression from a Library. This method does a test compilation before it returns, so that if there's something wrong with the expression this method will throw a CompilationException, but invocations of the returned Function on Libraries compatible with the supplied table ought not to. The returned function therefore does not need to declare throwing a CompilerException. If for some reason the deferred compilations do fail, a RuntimeException is returned.
      Parameters:
      table - table from which libraries will be derived
      expr - expression to compile
      clazz - required result type of expression, or null for automatic
      Throws:
      gnu.jel.CompilationException
    • compileExpressions

      public static gnu.jel.CompiledExpression[] compileExpressions(StarTableJELRowReader reader, String[] exprs) throws IOException
      Compiles a set of expressions relating to a table.

      Any CompilationExceptions are rethrown as IOExceptions; this method should therefore generally be used only if the expressions are expected to be free from errors (have been compiled before).

      Parameters:
      reader - table reader
      exprs - strings giving JEL expressions to be compiled
      Returns:
      array with one compiled expression for each input string
      Throws:
      IOException - in case of any CompilationException
    • toIOException

      public static IOException toIOException(gnu.jel.CompilationException e, String expr)
      Utility method to convert a CompilationException into an IOException.
      Parameters:
      e - compilation exception
      expr - expression for which compilation failed, to be reported in error message
    • getWrapperType

      public static Class<?> getWrapperType(Class<?> clazz)
      Returns a non-primitive version of a given class. If clazz is a non-primitive type, it will be returned, otherwise the wrapper class corresponding to the primitive type of clazz will be returned (e.g. Integer for int).
      Parameters:
      clazz - input class
      Returns:
      non-primitive class matching clazz