/*
* Copyright 2006-2014 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 org.springframework.batch.sample.common;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Iterator;
import java.util.List;
import javax.sql.DataSource;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.batch.core.ExitStatus;
import org.springframework.batch.core.StepExecution;
import org.springframework.batch.core.StepExecutionListener;
import org.springframework.batch.item.ItemReader;
import org.springframework.batch.item.ReaderNotOpenException;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.jdbc.core.JdbcOperations;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.simple.ParameterizedRowMapper;
import org.springframework.util.Assert;
import org.springframework.util.SerializationUtils;
/**
* Thread-safe database {@link ItemReader} implementing the process indicator
* pattern.
*
* To achieve restartability use together with {@link StagingItemProcessor}.
*/
public class StagingItemReader<T> implements ItemReader<ProcessIndicatorItemWrapper<T>>, StepExecutionListener,
InitializingBean, DisposableBean {
private static Log logger = LogFactory.getLog(StagingItemReader.class);
private StepExecution stepExecution;
private final Object lock = new Object();
private volatile boolean initialized = false;
private volatile Iterator<Long> keys;
private JdbcOperations jdbcTemplate;
public void setDataSource(DataSource dataSource) {
jdbcTemplate = new JdbcTemplate(dataSource);
}
@Override
public void destroy() throws Exception {
initialized = false;
keys = null;
}
@Override
public final void afterPropertiesSet() throws Exception {
Assert.notNull(jdbcTemplate, "You must provide a DataSource.");
}
private List<Long> retrieveKeys() {
synchronized (lock) {
return jdbcTemplate.query(
"SELECT ID FROM BATCH_STAGING WHERE JOB_ID=? AND PROCESSED=? ORDER BY ID",
new ParameterizedRowMapper<Long>() {
@Override
public Long mapRow(ResultSet rs, int rowNum) throws SQLException {
return rs.getLong(1);
}
},
stepExecution.getJobExecution().getJobId(), StagingItemWriter.NEW);
}
}
@Override
public ProcessIndicatorItemWrapper<T> read() {
if (!initialized) {
throw new ReaderNotOpenException("Reader must be open before it can be used.");
}
Long id = null;
synchronized (lock) {
if (keys.hasNext()) {
id = keys.next();
}
}
logger.debug("Retrieved key from list: " + id);
if (id == null) {
return null;
}
@SuppressWarnings("unchecked")
T result = (T) jdbcTemplate.queryForObject("SELECT VALUE FROM BATCH_STAGING WHERE ID=?",
new ParameterizedRowMapper<Object>() {
@Override
public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
byte[] blob = rs.getBytes(1);
return SerializationUtils.deserialize(blob);
}
}, id);
return new ProcessIndicatorItemWrapper<T>(id, result);
}
@Override
public ExitStatus afterStep(StepExecution stepExecution) {
return null;
}
@Override
public void beforeStep(StepExecution stepExecution) {
this.stepExecution = stepExecution;
synchronized (lock) {
if (keys == null) {
keys = retrieveKeys().iterator();
logger.info("Keys obtained for staging.");
initialized = true;
}
}
}
}