com.expedia.seiso.domain.service.search.QueryFactory.java Source code

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Here is the source code for com.expedia.seiso.domain.service.search.QueryFactory.java

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/* 
 * Copyright 2013-2015 the original author or authors.
 * 
 * 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 com.expedia.seiso.domain.service.search;

import java.util.ArrayList;
import java.util.List;
import java.util.Set;

import javax.persistence.EntityManager;
import javax.persistence.Query;
import javax.validation.constraints.NotNull;

import org.hibernate.validator.constraints.NotEmpty;
import org.springframework.util.Assert;

// TODO revisit string approach, look at replacing with criteria to protect against injection

/**
 * @author Ken Van Eyk
 */
public class QueryFactory {
    private String calculateTableAlias(String entityName) {
        String tableAlias = entityName.substring(0, 1).toLowerCase();

        return tableAlias;
    }

    private void appendQueryRoot(StringBuilder stringBuilder, String entityName, String tableAlias) {
        stringBuilder.append("from ").append(entityName).append(" ").append(tableAlias).append(" where ");
    }

    private List<String> appendQueryLikeClausesForField(StringBuilder queryStringBuilder, String tableAlias,
            String fieldName, Set<String> searchTokens) {
        List<String> parameterNames = new ArrayList<String>();

        if (queryStringBuilder == null) {
            queryStringBuilder = new StringBuilder();
        }

        for (int tokenIndex = 0; tokenIndex < searchTokens.size(); tokenIndex++) {
            String parameterName = new StringBuilder("param").append(tokenIndex).toString();
            parameterNames.add(parameterName);
            queryStringBuilder.append(tableAlias).append(".").append(fieldName).append(" like :")
                    .append(parameterName).append(" ");
            if (tokenIndex < searchTokens.size() - 1) {
                queryStringBuilder.append("or ");
            }
        }

        return parameterNames;
    }

    private List<String> appendQueryString(StringBuilder queryStringBuilder, String entityName,
            Set<String> fieldNames, Set<String> searchTokens) {
        List<String> parameterNames = new ArrayList<String>();

        String tableAlias = this.calculateTableAlias(entityName);
        this.appendQueryRoot(queryStringBuilder, entityName, tableAlias);

        int fieldNamesIndex = 0;
        for (String fieldName : fieldNames) {
            // TODO improve this, technically the parameter names are created every time we call this append method -
            // they should always be consistent but it is wasting resources a bit
            parameterNames.addAll(
                    this.appendQueryLikeClausesForField(queryStringBuilder, tableAlias, fieldName, searchTokens));
            if (++fieldNamesIndex < fieldNames.size()) {
                queryStringBuilder.append("or ");
            }
        }

        return parameterNames;
    }

    private void setParameters(Query jpaQuery, List<String> parameterNames, Set<String> searchTokens) {
        int parameterIndex = 0;
        for (String searchToken : searchTokens) {
            jpaQuery.setParameter(parameterNames.get(parameterIndex++), searchToken);
        }
    }

    public Query buildQuery(@NotEmpty String entityName, @NotNull EntityManager entityManager,
            @NotNull Set<String> fieldNames, @NotNull Set<String> searchTokens) {
        Query jpaQuery = null;

        Assert.notEmpty(fieldNames, "empty field names");
        Assert.notEmpty(searchTokens, "empty search tokens");

        StringBuilder queryStringBuilder = new StringBuilder();

        List<String> parameterNames = this.appendQueryString(queryStringBuilder, entityName, fieldNames,
                searchTokens);
        jpaQuery = entityManager.createQuery(queryStringBuilder.toString());
        this.setParameters(jpaQuery, parameterNames, searchTokens);

        return jpaQuery;
    }
}