Field Detail

• CLASSES_PROPERTY

  public static final java.lang.String CLASSES_PROPERTY

  System property name for adding colon-separated list of additional classnames containing static methods.

  See Also:

  Constant Field Values

Constructor Detail

• JELUtils

  public JELUtils​()

Method Detail

• getLibrary

  public static gnu.jel.Library getLibrary​(JELRowReader reader)

  Returns a JEL Library suitable for expression evaluation.

  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

• 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 java.util.List<java.lang.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 java.lang.Class getExpressionType​(gnu.jel.Library lib,
                                                  uk.ac.starlink.table.StarTable table,
                                                  java.lang.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,
                                         java.lang.String expr,
                                         java.lang.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,
                                                   java.lang.String expr,
                                                   java.lang.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,
                                                   java.lang.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,
                                            java.lang.String expr,
                                            java.lang.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

• toIOException

  public static java.io.IOException toIOException​(gnu.jel.CompilationException e,
                                                  java.lang.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 java.lang.Class getWrapperType​(java.lang.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