Question

我的Java迁移目前没有实现MigrationChecksumProvider接口。我想知道他们是否应该。

我不明白校验球在Flyway中扮演什么角色。请问有人向我解释一下吗？此外，如果我实现MigrationChecksumProvider，如何为给定的迁移计算校验和？

谢谢。

Answer 1

我认为大多数时候你想根据相关类文件的内容来计算校验和。我们这样做......

import java.io.IOException;
import java.io.InputStream;
import java.util.zip.CRC32;

import org.flywaydb.core.api.migration.jdbc.JdbcMigration;
import org.flywaydb.core.internal.util.FileCopyUtils;
import org.flywaydb.core.internal.util.logging.Log;
import org.flywaydb.core.internal.util.logging.LogFactory;

/**
 * Utility class for checksum calculations.
 * 
 */
public final class Checksums {

    private static final Log LOG = LogFactory.getLog(Checksums.class);

    private Checksums() {
        super(); // singleton
    }

    /**
     * Calculates a checksum based on the given JdbcMigration. It builds the checksum from the byte content of the given
     * migration class file using the same {@link CRC32} method as used by
     * {@link org.flywaydb.core.internal.resolver.sql.SqlMigrationResolver}
     * 
     * @param migration
     * @return the checksum
     */
    public static final Integer checksum(JdbcMigration migration) {
        Integer checksum = null;

        Class<?> migrationClass = migration.getClass();
        String migrationClassFilePath = migrationClass.getName().replace(".", System.getProperty("file.separator")) + ".class";
        InputStream inputStream = null;

        try {
            inputStream = ClassLoader.getSystemResourceAsStream(migrationClassFilePath);
            byte[] classContent = FileCopyUtils.copyToByteArray(inputStream);
            final CRC32 crc32 = new CRC32();
            crc32.update(classContent);
            checksum = (int) crc32.getValue();
        } catch (IOException ioe) {
            LOG.error("Problem calculating checksum for class " + migrationClass.getName(), ioe);
        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException ioe) {
                    LOG.error("Problem closing input stream to " + migrationClassFilePath, ioe);
                }
            }
        }
        return checksum;
    }    
}

然后你可以创建一个类似于

的基类

public abstract class JdbcMigrationWithChecksum implements JdbcMigration, MigrationChecksumProvider {

    @Override
    public Integer getChecksum() {
        return Checksums.checksum(this);
    }
}

Answer 2

校验和用于迁移的（意外）更改检测，这将无法保证可以完全重新创建架构。

对于Java迁移，天空是您可以执行的操作的限制。因此，您可以调用如何实现校验和以检测更改。

在Java迁移中实现校验和

2 个答案: