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将对象转换为Blob对象时出现问题

serialization java

GustyWind · 技术社区 · 14 年前

我有一个序列化的对象,需要转换为'blob'对象并存储到数据库中。以前我们存储的对象是由其他项目对象定义的,但不遵循序列化规则,因此遇到了许多问题,因此我们决定更改结构“blob”对象,它现在只包含基本对象(字符串、布尔值、整数等)。到目前为止,我们可以使所有属性都期望两个。

private byte[] encode(ScheduledReport schedSTDReport)
{
    byte[] bytes = null;
    try
    {
        ByteArrayOutputStream bos = new ByteArrayOutputStream(); 
        ObjectOutputStream oos = new ObjectOutputStream(bos);
        oos.writeObject(schedSTDReport);
        oos.flush(); 
        oos.close(); 
        bos.close();
        //byte [] data = bos.toByteArray();
        //ByteArrayOutputStream baos = new ByteArrayOutputStream();
        //GZIPOutputStream out = new GZIPOutputStream(baos);
        //XMLEncoder encoder = new XMLEncoder(out);
        //encoder.writeObject(schedSTDReport);
        //encoder.close();
        bytes = bos.toByteArray();
        //GZIPOutputStream out = new GZIPOutputStream(bos);
        //out.write(bytes);
        //bytes = bos.toByteArray();

    }

Blob包含

public class ScheduledReport extends ScheduledReportInfo implements Serializable {



    private SupervisoryScope                   _scope          = null;
    private Report                             _attributes     = null;
    private ScheduledReportScheduleBase        _schedule       = null;
    private HashMap                            selectionList   = new HashMap();
    private EmailInfo                          _emailInfo      = null;
    private String                             _pdfFileName    = null;
    private short                              _baseDateOffset = -1;

在report对象中有以下属性

private String     deflt = null;
private Object     guiValue = null;
protected Object   serverValue = null;

变量对象可以有任何类似的数组列表、字符串、布尔值或类对象。但一旦解码成实际的对象,它就需要类型转换成它是什么类型,我们的目标是将这个对象转换成任何原始类型,并存储和检索回原始值。本质上,我们认为每个对象都是字符串,对象类型附加在字符串上,如“1_integer”、“Y_Boolean”并转换为blob,同时恢复拆分字符串并将字符串用作反射的一部分,以获取要转换的对象类型。但这不可行也不正确。任何想法。

1 回复 | 直到 14 年前

npinti 14 年前

如果分解对象并存储单独的字段而不是一大块数据,岂不是更简单些吗?

另一方面,你可能想试试 Hibernate here

package org.kodejava.example.hibernate.app;

import java.util.Date;

import org.hibernate.Session;

public class LabelManager {
    private Label getLabel(Long id) {
        Session session = SessionFactoryHelper.getSessionFactory().getCurrentSession();

        session.beginTransaction();

        /*
         * We get back Label object from database by calling the Session object
         * get() method and passing the object type and the object id to be
         * read.
         */
        Label label = (Label) session.get(Label.class, id);
        session.getTransaction().commit();

        return label;
    }

    private void saveLabel(Label label) {
        /*
         * To save an object we first get a session by calling getCurrentSession()
         * method from the SessionFactoryHelper class. Next we create a new
         * transcation, save the Label object and commit it to database,
         */
        Session session = SessionFactoryHelper.getSessionFactory().getCurrentSession();

        session.beginTransaction();        
        session.save(label);        
        session.getTransaction().commit();
    }

    public static void main(String[] args) {        
        LabelManager manager = new LabelManager();

        /*
         * Creates a Label object we are going to stored in the database. We
         * set the name, modified by and modified date information.
         */
        Label label = new Label();
        label.setName("Sony Music");
        label.setModifiedBy("admin");
        label.setModifiedDate(new Date());

        /*
         * Call the LabelManager saveLabel method.
         */
        manager.saveLabel(label);

        /*
         * Read the object back from database.
         */
        label = manager.getLabel(label.getId());
        System.out.println("Label = " + label);
    }    
}