spring-batch Neo4jItemReader 源码

  • 2022-08-16
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spring-batch Neo4jItemReader 代码

文件路径:/spring-batch-infrastructure/src/main/java/org/springframework/batch/item/data/Neo4jItemReader.java

/*
 * Copyright 2012-2021 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
 *
 *      https://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.springframework.batch.item.data;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.neo4j.ogm.session.Session;
import org.neo4j.ogm.session.SessionFactory;

import org.springframework.batch.item.ItemReader;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * <p>
 * Restartable {@link ItemReader} that reads objects from the graph database Neo4j via a
 * paging technique.
 * </p>
 *
 * <p>
 * It executes cypher queries built from the statement fragments provided to retrieve the
 * requested data. The query is executed using paged requests of a size specified in
 * {@link #setPageSize(int)}. Additional pages are requested as needed when the
 * {@link #read()} method is called. On restart, the reader will begin again at the same
 * number item it left off at.
 * </p>
 *
 * <p>
 * Performance is dependent on your Neo4J configuration (embedded or remote) as well as
 * page size. Setting a fairly large page size and using a commit interval that matches
 * the page size should provide better performance.
 * </p>
 *
 * <p>
 * This implementation is thread-safe between calls to
 * {@link #open(org.springframework.batch.item.ExecutionContext)}, however you should set
 * <code>saveState=false</code> if used in a multi-threaded environment (no restart
 * available).
 * </p>
 *
 * @author Michael Minella
 * @author Mahmoud Ben Hassine
 * @deprecated since 5.0 in favor of the item reader from
 * https://github.com/spring-projects/spring-batch-extensions/blob/main/spring-batch-neo4j
 */
@Deprecated
public class Neo4jItemReader<T> extends AbstractPaginatedDataItemReader<T> implements InitializingBean {

	protected Log logger = LogFactory.getLog(getClass());

	private SessionFactory sessionFactory;

	private String startStatement;

	private String returnStatement;

	private String matchStatement;

	private String whereStatement;

	private String orderByStatement;

	private Class<T> targetType;

	private Map<String, Object> parameterValues;

	/**
	 * Optional parameters to be used in the cypher query.
	 * @param parameterValues the parameter values to be used in the cypher query
	 */
	public void setParameterValues(Map<String, Object> parameterValues) {
		this.parameterValues = parameterValues;
	}

	protected final Map<String, Object> getParameterValues() {
		return this.parameterValues;
	}

	/**
	 * The start segment of the cypher query. START is prepended to the statement provided
	 * and should <em>not</em> be included.
	 * @param startStatement the start fragment of the cypher query.
	 */
	public void setStartStatement(String startStatement) {
		this.startStatement = startStatement;
	}

	/**
	 * The return statement of the cypher query. RETURN is prepended to the statement
	 * provided and should <em>not</em> be included
	 * @param returnStatement the return fragment of the cypher query.
	 */
	public void setReturnStatement(String returnStatement) {
		this.returnStatement = returnStatement;
	}

	/**
	 * An optional match fragment of the cypher query. MATCH is prepended to the statement
	 * provided and should <em>not</em> be included.
	 * @param matchStatement the match fragment of the cypher query
	 */
	public void setMatchStatement(String matchStatement) {
		this.matchStatement = matchStatement;
	}

	/**
	 * An optional where fragment of the cypher query. WHERE is prepended to the statement
	 * provided and should <em>not</em> be included.
	 * @param whereStatement where fragment of the cypher query
	 */
	public void setWhereStatement(String whereStatement) {
		this.whereStatement = whereStatement;
	}

	/**
	 * A list of properties to order the results by. This is required so that subsequent
	 * page requests pull back the segment of results correctly. ORDER BY is prepended to
	 * the statement provided and should <em>not</em> be included.
	 * @param orderByStatement order by fragment of the cypher query.
	 */
	public void setOrderByStatement(String orderByStatement) {
		this.orderByStatement = orderByStatement;
	}

	protected SessionFactory getSessionFactory() {
		return sessionFactory;
	}

	/**
	 * Establish the session factory for the reader.
	 * @param sessionFactory the factory to use for the reader.
	 */
	public void setSessionFactory(SessionFactory sessionFactory) {
		this.sessionFactory = sessionFactory;
	}

	/**
	 * The object type to be returned from each call to {@link #read()}
	 * @param targetType the type of object to return.
	 */
	public void setTargetType(Class<T> targetType) {
		this.targetType = targetType;
	}

	protected final Class<T> getTargetType() {
		return this.targetType;
	}

	protected String generateLimitCypherQuery() {
		StringBuilder query = new StringBuilder(128);

		query.append("START ").append(startStatement);
		query.append(matchStatement != null ? " MATCH " + matchStatement : "");
		query.append(whereStatement != null ? " WHERE " + whereStatement : "");
		query.append(" RETURN ").append(returnStatement);
		query.append(" ORDER BY ").append(orderByStatement);
		query.append(" SKIP " + (pageSize * page));
		query.append(" LIMIT " + pageSize);

		String resultingQuery = query.toString();

		if (logger.isDebugEnabled()) {
			logger.debug(resultingQuery);
		}

		return resultingQuery;
	}

	/**
	 * Checks mandatory properties
	 *
	 * @see InitializingBean#afterPropertiesSet()
	 */
	@Override
	public void afterPropertiesSet() throws Exception {
		Assert.state(sessionFactory != null, "A SessionFactory is required");
		Assert.state(targetType != null, "The type to be returned is required");
		Assert.state(StringUtils.hasText(startStatement), "A START statement is required");
		Assert.state(StringUtils.hasText(returnStatement), "A RETURN statement is required");
		Assert.state(StringUtils.hasText(orderByStatement), "A ORDER BY statement is required");
	}

	@SuppressWarnings("unchecked")
	@Override
	protected Iterator<T> doPageRead() {
		Session session = getSessionFactory().openSession();

		Iterable<T> queryResults = session.query(getTargetType(), generateLimitCypherQuery(), getParameterValues());

		if (queryResults != null) {
			return queryResults.iterator();
		}
		else {
			return new ArrayList<T>().iterator();
		}
	}

}

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