org.rnott.mock.ExpressionLanguageEvaluator.java Source code

Introduction

Here is the source code for org.rnott.mock.ExpressionLanguageEvaluator.java

Source

/*
 * Copyright 2016 Randy Nott
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.rnott.mock;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import org.antlr.v4.runtime.CommonToken;
import org.antlr.v4.runtime.ParserRuleContext;
import org.rnott.mock.ExpressionLanguageParser.ExpressionContext;
import org.rnott.mock.ExpressionLanguageParser.LiteralContext;
import org.rnott.mock.ExpressionLanguageParser.MethodContext;
import org.rnott.mock.ExpressionLanguageParser.ParameterContext;
import org.rnott.mock.ExpressionLanguageParser.ParametersContext;
import org.rnott.mock.ExpressionLanguageParser.PropertyContext;
import org.rnott.mock.ExpressionLanguageParser.VerbatimContext;

/**
 * Expression Language (EL) evaluator. Instances of this type are used to transform
 * a service request according to the EL syntax.
 */
public class ExpressionLanguageEvaluator extends ExpressionLanguageBaseListener {

    private StringBuilder content = new StringBuilder();

    /**
     * Get the transformed text.
     * <p>
     * @return the transformed text.
     */
    public String getText() {
        return content.toString();
    }

    /**
     * Process verbatim text.
     * <p>
     * @param the EL context.
     */
    @Override
    public void enterVerbatim(VerbatimContext ctx) {
        // append verbatim text
        // skip escape character
        Object obj = ctx.getChild(0).getPayload();
        if (obj instanceof CommonToken && ((CommonToken) obj).getType() == ExpressionLanguageParser.ESCAPED) {
            content.append(ctx.getText().substring(1));
        } else {
            content.append(ctx.getText());
        }
    }

    /**
     * Begin processing an EL expression.
     * <p>
     * @param ctx the EL expression context.
     */
    @Override
    public void enterExpression(ExpressionContext ctx) {
        // expression is an EL method or property
        super.enterExpression(ctx);
        ParserRuleContext p = (ParserRuleContext) ctx.getChild(0);
        if (p == null) {
            //throw new IllegalStateException( ctx. );
        }
        switch (p.getRuleIndex()) {
        case ExpressionLanguageParser.RULE_method:
            // append invocation of an EL method
            content.append(evaluate((MethodContext) p));
            break;
        case ExpressionLanguageParser.RULE_property:
            // append resolution of an EL property
            content.append(evaluate((PropertyContext) p));
            break;
        }
    }

    /**
     * Evaluate an EL literal.
     * <p>
     * @param ctx the EL literal context.
     * @return the resolved value.
     */
    private Object evaluate(LiteralContext ctx) {
        String s = ctx.getText();
        switch (((CommonToken) ctx.getChild(0).getPayload()).getType()) {
        case ExpressionLanguageParser.STRING:
            // remove surrounding quotes
            return s.substring(1, s.length() - 1);
        case ExpressionLanguageParser.INT:
            // parse as integer
            return Integer.parseInt(s);
        case ExpressionLanguageParser.LONG:
            // parse as long
            return Long.parseLong(s.substring(0, s.length() - 1));
        }
        return s;
    }

    /**
     * Evaluate an EL property.
     * <p>
     * @param ctx the EL property context.
     * @return the resolved value.
     * @throws IllegalStateException if the property specified by the expression
     * is not a request parameter.
     */
    private Object evaluate(PropertyContext ctx) {
        Map<String, String> params = MockContext.get().getParameters();
        String key = ctx.getChild(1).getText();
        if (params.containsKey(key)) {
            return params.get(key);
        }
        throw new IllegalStateException(
                "Property not present as a request parameter: " + key + " " + params.keySet());
    }

    /**
     * Evaluate an EL method.
     * <p>
     * @param ctx the EL method context.
     * @return the resolved value.
     * @throws IllegalStateException if the EL method specifies an unknown evaluator.
     */
    private Object evaluate(MethodContext ctx) {
        String s = ctx.getChild(1).getText();
        int pos = s.indexOf('.');
        String type = s.substring(0, pos);
        String method = s.substring(pos + 1);
        ParametersContext pc = (ParametersContext) ctx.getChild(2);
        List<Object> params = new ArrayList<Object>();
        for (int i = 1, count = pc.getChildCount() - 1; i < count; i++) {
            if (pc.getChild(i) instanceof ParameterContext) {
                ParserRuleContext p = (ParserRuleContext) pc.getChild(i).getChild(0);
                switch (p.getRuleIndex()) {
                case ExpressionLanguageParser.RULE_literal:
                    params.add(evaluate((LiteralContext) p));
                    break;
                case ExpressionLanguageParser.RULE_method:
                    params.add(evaluate((MethodContext) p));
                    break;
                case ExpressionLanguageParser.RULE_property:
                    params.add(evaluate((PropertyContext) p));
                    break;
                }
            }
        }

        return MockContext.get().getEvaluator(type).evaluate(method, params.toArray());
    }
}