Example usage for org.apache.commons.jexl3 JexlEngine createExpression

Introduction

In this page you can find the example usage for org.apache.commons.jexl3 JexlEngine createExpression.

Prototype

public final JexlExpression createExpression(String expression) 

Source Link

Document

Creates a JexlExpression from a String containing valid JEXL syntax.

Usage

From source file:com.epam.dlab.core.parser.ConditionEvaluate.java

/** Instantiate the engine to evaluate condition. 
 * @param columnNames the list of column names.
 * @param condition condition for filtering data.
 * @throws InitializationException/*from  ww  w.  j a  va 2s .c  o m*/
 */
public ConditionEvaluate(List<String> columnNames, String condition) throws InitializationException {
    //Replace : to . in column names
    List<String> colNames = new ArrayList<>(columnNames.size());
    for (int i = 0; i < columnNames.size(); i++) {
        String name = columnNames.get(i);
        if (name.indexOf(':') > -1 && condition.indexOf(name) > -1) {
            String newName = StringUtils.replaceChars(name, ':', '.');
            colNames.add(newName);
            condition = StringUtils.replace(condition, name, newName);
        } else {
            colNames.add(name);
        }
    }

    try {
        JexlEngine engine = new JexlBuilder().strict(true).silent(false).debug(true).create();
        expression = (Script) engine.createExpression(condition);
        jexlContext = new MapContext();
    } catch (Exception e) {
        throw new InitializationException(
                "Cannot initialize JEXL engine for condition: " + condition + ". " + e.getLocalizedMessage(),
                e);
    }

    // Create mapping of columns for evaluations. 
    List<String> names = new ArrayList<>();
    List<Integer> indexes = new ArrayList<>();
    for (List<String> variableList : expression.getVariables()) {
        String columnName = StringUtils.join(variableList, '.');
        int index = getColumnIndex(colNames, columnName);
        if (index == -1) {
            throw new InitializationException("Unknow source column name \"" + columnName + "\" in condition: "
                    + expression.getSourceText() + ". Known column names: "
                    + StringUtils.join(columnNames, ", ") + ".");
        }
        names.add(columnName);
        indexes.add(index);
    }

    this.columnNames = new String[names.size()];
    this.columnIndexes = new int[indexes.size()];
    for (int i = 0; i < indexes.size(); i++) {
        this.columnNames[i] = names.get(i);
        this.columnIndexes[i] = indexes.get(i);
    }
}

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