Package uk.ac.starlink.ttools.jel
Class JELUtils
- java.lang.Object
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- uk.ac.starlink.ttools.jel.JELUtils
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public class JELUtils extends java.lang.Object
This class provides some utility methods for use with the JEL expression compiler.- Since:
- 11 Feb 2005
- Author:
- Mark Taylor (Starlink)
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Field Summary
Fields Modifier and Type Field Description static java.lang.String
CLASSES_PROPERTY
System property name for adding colon-separated list of additional classnames containing static methods.
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Constructor Summary
Constructors Constructor Description JELUtils()
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static void
checkExpressionType(gnu.jel.Library lib, uk.ac.starlink.table.StarTable table, java.lang.String expr, java.lang.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, java.lang.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, java.lang.String expr, java.lang.Class<?> clazz)
Compiles an expression in the context of a given table with a required type for the result.static JELQuantity
compileQuantity(gnu.jel.Library lib, StarTableJELRowReader jelRdr, java.lang.String expr, java.lang.Class<?> clazz)
Compiles an expression in the context of a table reader to give a JELQuantity.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.static java.lang.Class<?>
getExpressionType(gnu.jel.Library lib, uk.ac.starlink.table.StarTable table, java.lang.String expr)
Gives the return type of an expression.static gnu.jel.Library
getLibrary(JELRowReader reader)
Returns a JEL Library suitable for expression evaluation.static java.util.List<java.lang.Class<?>>
getStaticClasses()
Returns the list of classes whose static methods will be mapped into the JEL evaluation namespace.static java.lang.Class<?>
getWrapperType(java.lang.Class<?> clazz)
Returns a non-primitive version of a given class.static java.io.IOException
toIOException(gnu.jel.CompilationException e, java.lang.String expr)
Utility method to convert a CompilationException into an IOException.
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Field Detail
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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
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Method Detail
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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
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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
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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
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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 librarytable
- context tableexpr
- string representation of the expression- Returns:
- class which evaluation of expr using lib will return
- Throws:
gnu.jel.CompilationException
- if expr cannot be compiled
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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 librarytable
- context tableexpr
- string representation of the expressionclazz
- 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)
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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 librarytable
- context tableexpr
- expression stringclazz
- required class of resulting expression- Returns:
- compiled expression
- Throws:
gnu.jel.CompilationException
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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 librarytable
- context tableexpr
- expression string- Returns:
- compiled expression
- Throws:
gnu.jel.CompilationException
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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 thecompile
methods, but it provides additional metadata if it can be retrieved from the table context.- Parameters:
lib
- JEL libraryjelRdr
- context table readerexpr
- expression stringclazz
- required return type of compiled expression, or null if no requirement- Returns:
- compiled quantity
- Throws:
gnu.jel.CompilationException
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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 exceptionexpr
- expression for which compilation failed, to be reported in error message
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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
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