Question

For this question, we want to avoid having to write a special query since the query would have to be different across multiple databases. Using only hibernate criteria, we want to be able to escape special characters.

This situation is the reason for needing the ability to escape special characters:

Assume that we have table ‘foo’ in the database. Table ‘foo’ contains only 1 field, called ‘name’. The ‘name’ field can contain characters that may be considered special in a database. Two examples of such a name are ‘name_1’ and ‘name%1’. Both the ‘_’ and ‘%’ are special characters, at least in Oracle. If a user wants to search for one of these examples after they are entered in the database, problems may occur.

criterion = Restrictions.ilike("name", searchValue, MatchMode.ANYWHERE);
return findByCriteria(null, criterion);

In this code, ‘searchValue’ is the value that the user has given the application to use for its search. If the user wants to search for ‘%’, the user is going to be returned with every ‘foo’ entry in the database. This is because the ‘%’ character represents the “any number of characters” wildcard for string matching and the SQL code that hibernate produces will look like:

select * from foo where name like '%' 

Is there a way to tell hibernate to escape certain characters, or to create a workaround that is not database type specific?

Answer 1

LikeExpression’s constructors are all protected, so it’s not a viable option. Also, it has problems of its own.

A colleague and I created a patch which works pretty well. The gist of the patch is that for the LikeExpression constructor which consumes a MatchMode, we escape the special characters. For the constructor which consumes a Character (the escape character), we assume the user escapes the special characters on their own.

We also parameterized the escape character to ensure that it can’t corrupt the SQL query if they use something like \ or a quote character.

package org.hibernate.criterion;

import org.hibernate.Criteria;
import org.hibernate.HibernateException;
import org.hibernate.dialect.Dialect;
import org.hibernate.engine.TypedValue;

public class LikeExpression implements Criterion {
    private final String propertyName;
    private final String value;
    private final Character escapeChar;

    protected LikeExpression(
            String propertyName,
            Object value) {
        this(propertyName, value.toString(), (Character) null);
    }

    protected LikeExpression(
            String propertyName,
            String value,
            MatchMode matchMode) {
        this( propertyName, matchMode.toMatchString( value
                .toString()
                .replaceAll("!", "!!")
                .replaceAll("%", "!%")
                .replaceAll("_", "!_")), '!' );
    }

    protected LikeExpression(
            String propertyName,
            String value,
            Character escapeChar) {
        this.propertyName = propertyName;
        this.value = value;
        this.escapeChar = escapeChar;
    }

    public String toSqlString(
            Criteria criteria,
            CriteriaQuery criteriaQuery) throws HibernateException {
        Dialect dialect = criteriaQuery.getFactory().getDialect();
        String[] columns = criteriaQuery.getColumnsUsingProjection( criteria, propertyName );
        if ( columns.length != 1 ) {
            throw new HibernateException( "Like may only be used with single-column properties" );
        }
        String lhs = lhs(dialect, columns[0]);
        return lhs + " like ?" + ( escapeChar == null ? "" : " escape ?" );

    }

    public TypedValue[] getTypedValues(
            Criteria criteria,
            CriteriaQuery criteriaQuery) throws HibernateException {
        return new TypedValue[] {
                criteriaQuery.getTypedValue( criteria, propertyName, typedValue(value) ),
                criteriaQuery.getTypedValue( criteria, propertyName, escapeChar.toString() )
        };
    }

    protected String lhs(Dialect dialect, String column) {
        return column;
    }

    protected String typedValue(String value) {
        return value;
    }

}

If you’re wondering what the lhs and typedValue methods are for, the new IlikeExpression should answer those questions.

package org.hibernate.criterion;

import org.hibernate.dialect.Dialect;

public class IlikeExpression extends LikeExpression {

    protected IlikeExpression(
            String propertyName,
            Object value) {
        super(propertyName, value);
    }

    protected IlikeExpression(
            String propertyName,
            String value,
            MatchMode matchMode) {
        super(propertyName, value, matchMode);

    }

    protected IlikeExpression(
            String propertyName,
            String value,
            Character escapeChar) {
        super(propertyName, value, escapeChar);
    }

    @Override
    protected String lhs(Dialect dialect, String column) {
        return dialect.getLowercaseFunction() + '(' + column + ')';
    }

    @Override
    protected String typedValue(String value) {
        return super.typedValue(value).toLowerCase();
    }

}

After this, the only thing left is to make Restrictions use these new classes:

public static Criterion like(String propertyName, Object value) {
    return new LikeExpression(propertyName, value);
}

public static Criterion like(String propertyName, String value, MatchMode matchMode) {
    return new LikeExpression(propertyName, value, matchMode);
}

public static Criterion like(String propertyName, String value, Character escapeChar) {
    return new LikeExpression(propertyName, value, escapeChar);
}

public static Criterion ilike(String propertyName, Object value) {
    return new IlikeExpression(propertyName, value);
}

public static Criterion ilike(String propertyName, String value, MatchMode matchMode) {
    return new IlikeExpression(propertyName, value, matchMode);
}

public static Criterion ilike(String propertyName, String value, Character escapeChar) {
    return new IlikeExpression(propertyName, value, escapeChar);
}

Edit: Oh yeah. This works for Oracle. We’re not sure about other databases though.