Berkeley DB 中的突变错误

Question

我正在使用 Berkely DB，但出现一个错误，提示缺少突变。这是什么意思？

Exception: com.sleepycat.persist.evolve.IncompatibleClassException: Mutation is missing to evolve class: TopMoveDAO.TopMoveClass version: 0 Error: java.lang.ClassNotFoundException: TopMoveDAO.TopMoveClasscom.sleepycat.persist.evolve.IncompatibleClassException: Mutation is missing to evolve class: TopMoveDAO.TopMoveClass version: 0 Error: java.lang.ClassNotFoundException: TopMoveDAO.TopMoveClass

在 com.sleepycat.persist.impl.PersistCatalog.(PersistCatalog.java:365) 在 com.sleepycat.persist.impl.Store.(Store.java:180) 在 com.sleepycat.persist.EntityStore.(EntityStore.java:165) 在 TopMoveDAO.TopMovePut.setup(TopMovePut.java:40) 在 TopMoveDAO.TopMovePut.run(TopMovePut.java:59) 在 TopMoveDAO.TopMovePut.main(TopMovePut.java:84)

package TopMoveDAO;

import java.io.File;
import java.util.Timer;
import java.util.TimerTask;

import com.sleepycat.je.DatabaseException;
import com.sleepycat.je.Environment;
import com.sleepycat.je.EnvironmentConfig;

import com.sleepycat.persist.EntityStore;
import com.sleepycat.persist.StoreConfig; 

public class TopMovePut {

    //private static File envHome = new File("C:/dev/je-3.3.75/");
 private static File envHome = new File("C:/dev/db/berkeley");


    private Environment envmnt;
    private EntityStore store;
    private TopMoveDA sda; 


//Next we create a method that simply opens our database environment and entity store for us.

   // The setup() method opens the environment and store
    // for us.
    public void setup()
        throws DatabaseException {

        EnvironmentConfig envConfig = new EnvironmentConfig();
        StoreConfig storeConfig = new StoreConfig();

        envConfig.setAllowCreate(true);
        storeConfig.setAllowCreate(true);

        // Open the environment and entity store
        envmnt = new Environment(envHome, envConfig);
       store = new EntityStore(envmnt, "EntityStore", storeConfig);
    } 

//We also need a method to close our environment and store.

    // Close our environment and store.
    public void shutdown()
        throws DatabaseException {

        store.close();
        envmnt.close();
    } 



//Populate the entity store
private void run()
    throws DatabaseException {

    setup();

    // Open the data accessor. This is used to store
    // persistent objects.
    sda = new TopMoveDA(store);

    // Instantiate and store some entity classes

    PriceElement pe1 = new PriceElement();

    pe1.setSecCode("UNO");
    pe1.setLastPrice(1);

    sda.pIdx.put(pe1);

    shutdown();
} 

//main
public static void main(String args[]) {
    //SimpleStorePut ssp = new SimpleStorePut();
    TopMovePut tmp = new TopMovePut();
    try {
        //ssp.run();
     tmp.run();
    } catch (DatabaseException dbe) {
        System.err.println("TopMovePut: " + dbe.toString());
        dbe.printStackTrace();
    } catch (Exception e) {
        System.out.println("Exception: " + e.toString());
        e.printStackTrace();
    }
    System.out.println("All done - TopMovePut.");
}

} 

Answer 1

您必须编写一个突变来发展您的数据库。删除数据库并不能解决问题，只能绕过它（如果您还没有部署到生产环境，这很好，但如果您不想丢失现有数据，请编写突变。）

对持久实体的某些更改由 Berkley db 自动处理，例如添加字段。涉及删除数据或重命名字段的通常需要您编写显式突变。当您开始使用突变时，您还必须使用突变将引用的版本号注释您的实体 - 即使自动处理突变，您也必须增加版本号。当您进行重大的结构更改（例如使用不同的主键）时，您将不得不进行整个存储转换。

在复制环境中演进数据库时要小心。我强烈建议阅读以下内容：

Package com.sleepycat.persist.evolve (Oracle - Berkeley DB Java Edition API)

Answer 2

您必须每次都删除现有的数据库。