Java IO流 之 实现数据库

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http://www.verejava.com/?id=16994748096921

package com.database;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.Iterator;

public class TestDatabase
{
    public static void testAdd()
    {
        try
        {
            DatabaseStore ds=DatabaseStore.openDatabase("test.db");
            
            ByteArrayOutputStream baos=new ByteArrayOutputStream();
            DataOutputStream dos=new DataOutputStream(baos);
            dos.writeInt(30);
            dos.writeBoolean(true);
            dos.writeDouble(100.5);
            dos.writeUTF("李军");
            
            ds.addRecord(baos.toByteArray());
        } catch (IOException e)
        {
            e.printStackTrace();
        }
        
    }
    
    public static void testUpdate()
    {
        try
        {
            DatabaseStore ds=DatabaseStore.openDatabase("test.db");
            
            ByteArrayOutputStream baos=new ByteArrayOutputStream();
            DataOutputStream dos=new DataOutputStream(baos);
            dos.writeInt(30);
            dos.writeBoolean(true);
            dos.writeDouble(200.5);
            dos.writeUTF("张山");
            
            ds.setRecord(2, baos.toByteArray());
        } catch (IOException e)
        {
            e.printStackTrace();
        }
        
    }
    
    public static void testDelete()
    {
        DatabaseStore ds=DatabaseStore.openDatabase("test.db");
        
        ds.deleteRecord(3);
        
    }
    
    public static void testGet()
    {
        DatabaseStore ds=DatabaseStore.openDatabase("test.db");
        Iterator<Record> iter=ds.getRecords();
        try
        {
            while(iter.hasNext())
            {
                Record record=iter.next();
                ByteArrayInputStream bais=new ByteArrayInputStream(record.getData());
                DataInputStream dis=new DataInputStream(bais);
                    System.out.println(record.getId()+","+dis.readInt()+","+dis.readBoolean()+","+dis.readDouble()+","+dis.readUTF());
            }
        } catch (IOException e)
        {
            e.printStackTrace();
        }
        
    }
    public static void main(String[] args)
    {
        testDelete();
        testGet();
    }
}





package com.database;

import java.io.Serializable;

public class Record implements Serializable
{
    private int id;
    private byte[] data;
    
    public Record(int id, byte[] data)
    {
        super();
        this.id = id;
        this.data = data;
    }
    public int getId()
    {
        return id;
    }
    public void setId(int id)
    {
        this.id = id;
    }
    public byte[] getData()
    {
        return data;
    }
    public void setData(byte[] data)
    {
        this.data = data;
    }
    
    
}





package com.database;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class DatabaseStore implements Serializable
{
    private static String databasePath;
    private static DatabaseStore ds=null;
    private  int id;//自动增长的 id
    private  List<Record> recordList;
    
    private DatabaseStore()
    {
        recordList=new ArrayList<Record>();
    }
    
    public static DatabaseStore openDatabase(String databaseName)
    {
        databasePath=System.getProperty("user.dir")+"/"+databaseName;
        File file=new File(databasePath);
        if(!file.exists())
        {
            ds=new DatabaseStore();
            writeObject();
        }
        ds=readObject();
        return ds;
    }
    
    public  boolean addRecord(byte[] data)
    {
        ds.id++;
        ds.recordList.add(new Record(ds.id, data));
        return writeObject();
    }
    
    public  boolean setRecord(int id,byte[] data)
    {
        for(int i=0;i<ds.recordList.size();i++)
        {
            Record record=ds.recordList.get(i);
            if(record.getId()==id)
            {
                record.setData(data);
                return writeObject();
            }
        }
        return false;
    }
    
    public  Iterator<Record> getRecords()
    {
        return ds.recordList.iterator();
    }
    
    public  boolean deleteRecord(int id)
    {
        for(int i=0;i<ds.recordList.size();i++)
        {
            Record record=ds.recordList.get(i);
            if(record.getId()==id)
            {
                ds.recordList.remove(i);
                return writeObject();
            }
        }
        return false;
    }
    
    public static boolean writeObject()
    {
        ObjectOutputStream oos=null;
        try
        {
            oos=new ObjectOutputStream(new FileOutputStream(new File(databasePath)));
            oos.writeObject(ds);
            oos.flush();
            return true;
        } catch (FileNotFoundException e)
        {
            e.printStackTrace();
        } catch (IOException e)
        {
            e.printStackTrace();
        }
        finally
        {
            try
            {
                oos.close();
            } catch (IOException e)
            {
                e.printStackTrace();
            }
        }
        return false;
    }
    
    public static DatabaseStore readObject()
    {
        ObjectInputStream ois=null;
        try
        {
            ois=new ObjectInputStream(new FileInputStream(new File(databasePath)));
            ds=(DatabaseStore)ois.readObject();
            return ds;
        } catch (FileNotFoundException e)
        {
            e.printStackTrace();
        } catch (IOException e)
        {
            e.printStackTrace();
        } catch (ClassNotFoundException e)
        {
            e.printStackTrace();
        }
        finally
        {
            try
            {
                ois.close();
            } catch (IOException e)
            {
                e.printStackTrace();
            }
        }
        return null;
    }
}

http://www.verejava.com/?id=16994748096921

Java IO流 之 实现数据库

标签：www.   com   cat   int   get   false   ext   AC   ==   

原文地址：https://www.cnblogs.com/verejava/p/9227228.html