Class ExpressionBuilder

java/org/apache/el/lang/ExpressionBuilder.java:48–329

Builds compiled EL expressions from parsed AST nodes.

 * Builds compiled EL expressions from parsed AST nodes.
 */
public final class ExpressionBuilder implements NodeVisitor {

    private static final SynchronizedStack<ELParser> parserCache = new SynchronizedStack<>();

    private static final int CACHE_SIZE;
    private static final String CACHE_SIZE_PROP = "org.apache.el.ExpressionBuilder.CACHE_SIZE";

    static {
        String cacheSizeStr = System.getProperty(CACHE_SIZE_PROP, "5000");
        CACHE_SIZE = Integer.parseInt(cacheSizeStr);
    }

    private static final ConcurrentCache<String,Node> expressionCache = new ConcurrentCache<>(CACHE_SIZE);

    private FunctionMapper fnMapper;

    private VariableMapper varMapper;

    private final String expression;

    /**
     * Creates a new ExpressionBuilder for the given expression and context.
     *
     * @param expression the EL expression string
     * @param ctx the EL context
     * @throws ELException if the expression is invalid
     */
    public ExpressionBuilder(String expression, ELContext ctx) throws ELException {
        this.expression = expression;

        FunctionMapper ctxFn = ctx.getFunctionMapper();
        VariableMapper ctxVar = ctx.getVariableMapper();

        if (ctxFn != null) {
            this.fnMapper = new FunctionMapperFactory(ctxFn);
        }
        if (ctxVar != null) {
            this.varMapper = new VariableMapperFactory(ctxVar);
        }
    }

    /**
     * Creates a parsed AST node for the given expression string.
     *
     * @param expr the expression string to parse
     * @return the parsed AST node
     * @throws ELException if parsing fails
     */
    public static Node createNode(String expr) throws ELException {
        return createNodeInternal(expr);
    }

    private static Node createNodeInternal(String expr) throws ELException {
        if (expr == null) {
            throw new ELException(MessageFactory.get("error.null"));
        }

        Node n = expressionCache.get(expr);