持久化list

简单的做了持久化list的操作，方便网络传输数据，待时日可扩展为持久化队列系统或nosql数据库。为自主开发的的nosql作准备，以此为记：

package com.test.list;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.RandomAccessFile;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

/**
 *
 * 持久化list对象
 * 
 * @author LiuZiHeng
 * @version
 * @date 2010-8-16
 */
public class ListToBytes {

	public byte[] int2Bytes(int val) {
		byte[] bval = new byte[4];
		bval[0] = (byte)(val >> 24);
		bval[1] = (byte)((val << 8) >> 24);
		bval[2] = (byte)((val << 16)>>24);
		bval[3] = (byte)((val << 24) >> 24);
		
		return bval;
	}
	
	public void saveList(OutputStream out, List<A> list) throws IOException {
		if(list == null || list.size() == 0) {
			return;
		}
		
		for(int i = 0; i < list.size(); i++) {
			A a = list.get(i);
			byte[] objb = ObjectToBytes(a);
			
			out.write(int2Bytes(objb.length));
			out.write(objb);
		}
	}
	
	
	/**
	 * Object to byte[]
	 * 
	 * @param obj
	 * @return
	 */
	public byte[] ObjectToBytes(Object obj) {
		

		ObjectOutput out = null;
		try {
			ByteArrayOutputStream byteout = new ByteArrayOutputStream();
			out = new ObjectOutputStream(byteout);
			out.writeObject(obj);
			byte[] buf = byteout.toByteArray();

			return buf;
		} catch (IOException e) {
			return null;
		} finally {
			if (out != null) {
				try {
					out.close();
				} catch (IOException e) {
		
				}
			}
		}
	}

	/**
	 * byte[] to long
	 * 
	 * @param b
	 * @return
	 */
	public Object bytesToObject(byte[] b) {

		
		if (b.length > 0) {
			ObjectInput in = null;
			try {
				ByteArrayInputStream byteIn = new ByteArrayInputStream(b);
				in = new ObjectInputStream(byteIn);
				Object obj = in.readObject();

				if(obj != null) {
					return obj;
				}

			} catch (IOException e) {
				
				
			} catch (ClassNotFoundException e) {
				
				
			} finally {
				if (in != null) {
					try {
						in.close();
					} catch (IOException e) {
						
						
					}
				}
			}
			
			return null;
		} else {
		
			return null;
		}
	}
	
	public List getListFromSave(String filePath) {
		List<Object> l2 = new ArrayList<Object>();
		RandomAccessFile ram =null;
		try {
			ram = new RandomAccessFile(filePath, "r");
			
			while(ram.getFilePointer() != ram.length()) {
				int len = ram.readInt();
				byte[] buf = new byte[len];
				ram.readFully(buf);
				Object tmpa = bytesToObject(buf);
				l2.add(tmpa);
			}

		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
			if(ram != null) {
				try {
					ram.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
		
		return l2;
	}
	
	public static void main(String[] args) {
		ListToBytes ltb = new ListToBytes();
		List<A> list = new ArrayList<A>();
		A a = new A("a", 1);
		A a2 = new A("b", 2);
		A a3 = new A("c", 3);
		
		list.add(a);
		list.add(a2);
		list.add(a3);
		
		System.out.println("list before mod:");
		for(A ab : list) {
			System.out.println(ab.getA() + "->" + ab.getB());
		}
		
		
		FileOutputStream out = null;
		try {
			out = new FileOutputStream("./savelist/list.f");
			ltb.saveList(out, list);
			
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
			try {
				out.flush();
				out.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
		System.out.println("\nmod list:");
		list.get(0).setA("a11");
		for(A ab : list) {
			System.out.println(ab.getA() + "->" + ab.getB());
		}
		
		System.out.println("\nload it from save:");
		List l2 = ltb.getListFromSave("./savelist/list.f");
		
		for(Object a22 : l2) {
			System.out.println(((A)a22).getA() + "=" + ((A)a22).getB());
		}
	}
}

class A implements Serializable {

	private static final long serialVersionUID = -2278862909904751331L;
	
	private String a;
	private int b;
	
	public A(String a, int b) {
		this.a = a;
		this.b = b;
	}
	
	public void setA(String a) {
		this.a = a;
	}
	
	public String getA() {
		return a;
	}
	
	public void setB(int b) {
		this.b = b;
	}
	
	public int getB() {
		return b;
	}
}