locksdemo.JdbcLockService.java Source code

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Here is the source code for locksdemo.JdbcLockService.java

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/*
 * Copyright 2013-2014 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 locksdemo;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;
import java.util.UUID;

import javax.sql.DataSource;

import lombok.Setter;

import org.springframework.dao.IncorrectResultSizeDataAccessException;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.transaction.annotation.Isolation;
import org.springframework.transaction.annotation.Transactional;

/**
 * @author Dave Syer
 *
 */
public class JdbcLockService implements LockService {

    private final JdbcTemplate jdbcTemplate;

    @Setter
    private long expiry = 30000; // 30 seconds

    private RowMapper<Lock> rowMapper = new LockRowMapper();
    private String findAllQuery = "SELECT NAME,VALUE,EXPIRES FROM LOCKS";
    private String createQuery = "INSERT INTO LOCKS (NAME,VALUE,EXPIRES) VALUES (?,?,?)";
    private String deleteQuery = "DELETE FROM LOCKS WHERE NAME=? AND VALUE=?";
    private String refreshQuery = "UPDATE LOCKS SET EXPIRES=? WHERE NAME=? AND VALUE=?";
    private String findOneByNameQuery = "SELECT NAME,VALUE,EXPIRES FROM LOCKS WHERE NAME=?";

    public JdbcLockService(DataSource dataSource) {
        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }

    @Override
    public Iterable<Lock> findAll() {
        return jdbcTemplate.query(findAllQuery, rowMapper);
    }

    @Override
    @Transactional(isolation = Isolation.REPEATABLE_READ)
    public Lock create(String name) throws LockExistsException {
        Lock lock = getLock(name);
        if (lock != null) {
            if (lock.isExpired()) {
                jdbcTemplate.update(deleteQuery, lock.getName(), lock.getValue());
            } else {
                throw new LockExistsException();
            }
        }
        lock = new Lock(name, UUID.randomUUID().toString(), new Date(System.currentTimeMillis() + expiry));
        jdbcTemplate.update(createQuery, lock.getName(), lock.getValue(), lock.getExpires());
        return lock;
    }

    @Override
    @Transactional(isolation = Isolation.REPEATABLE_READ)
    public boolean release(String name, String value) throws LockNotHeldException {
        Lock lock = getLock(name);
        if (lock != null) {
            if (!lock.getValue().equals(value)) {
                throw new LockNotHeldException();
            }
            if (lock.isExpired()) {
                throw new LockNotHeldException();
            }
        }
        int changes = jdbcTemplate.update(deleteQuery, lock.getName(), lock.getValue());
        return changes > 0;
    }

    @Override
    @Transactional(isolation = Isolation.REPEATABLE_READ)
    public Lock refresh(String name, String value) throws LockNotHeldException {
        Lock lock = getLock(name);
        if (lock != null) {
            if (!lock.getValue().equals(value)) {
                throw new LockNotHeldException();
            }
            if (lock.isExpired()) {
                throw new LockNotHeldException();
            }
        }
        int changes = jdbcTemplate.update(refreshQuery, lock.getExpires(), lock.getName(), lock.getValue());
        if (changes > 0) {
            return lock;
        }
        throw new LockNotHeldException();
    }

    private Lock getLock(String name) {
        Lock lock = null;
        try {
            lock = jdbcTemplate.queryForObject(findOneByNameQuery, rowMapper, name);
        } catch (IncorrectResultSizeDataAccessException e) {
            // ignore
        }
        return lock;
    }

    private static class LockRowMapper implements RowMapper<Lock> {

        @Override
        public Lock mapRow(ResultSet rs, int rowNum) throws SQLException {
            return new Lock(rs.getString(1), rs.getString(2), rs.getTimestamp(3));
        }

    }

}