明天来讲讲序列化以及反序列化
Serializable接口，没有method，实现该接口表明能够序列化以及反序列化
ObjectOutputStream，将Object序列化为stream流
ObjectInputStream，通过stream流反序列化转化为Object
序列化时，计算出一个Serial version unique identifier标识这个class（平安的哈希值），并将这个哈希值其存储到stream中，而反序列化时java再次计算这个class的标识值（如果class类的定义已扭转则值也会发生变化），新计算的值与从stream取出来的值做比拟，如果不统一，示意该类的序列化版本与咱们领有的以后类定义不兼容。会产生InvalidClassException。
public class BankAccount implements Serializable { private String id; private int balance = 0; public BankAccount(String id){ this.id = id; } public BankAccount(String id, int startBalance){ this.id = id; balance = startBalance; } public String getId(){ return id; } public synchronized int getBalance(){ return balance; } public synchronized void deposit(int amount){ balance += amount; } public synchronized void withdrawal(int amount){ balance -= amount; }}序列化与反序列化办法
public class Main { public static void main(String[] args) { BankAccount ba = new BankAccount("10",500); ba.deposit(250); saveAccount(ba,"/Users/buxuesong/Documents/svn_code/demo/account.dat"); BankAccount bb = loadAccount("/Users/buxuesong/Documents/svn_code/demo/account.dat"); System.out.println(bb.getId() +" | " + bb.getBalance()); } private static void saveAccount(BankAccount ba, String fileName){ try(ObjectOutputStream os = new ObjectOutputStream(Files.newOutputStream(Paths.get(fileName)))){ os.writeObject(ba); }catch(Exception e){ System.out.println(e.getSuppressed() +" | "+ e.getMessage()); } } private static BankAccount loadAccount(String fileName){ BankAccount ba = null; try(ObjectInputStream oi = new ObjectInputStream(Files.newInputStream(Paths.get(fileName)))){ ba = (BankAccount) oi.readObject(); }catch(Exception e){ System.out.println(e.getSuppressed() +" | "+ e.getMessage()); } return ba; }}输入10 | 750当扭转了class的定义字段后，与原有序列化的惟一标识不同，导致无奈反序列化，这就须要自定义serialVersionUID，当前批改了该类，也会能够反序列化回来，只是新增的字段默认值为空或者是原始默认值（int的话就是0）
private static final long serialVersionUID = -23324324324L;还能够自定义序列化以及反序列化的办法，在BankAccount中
private void writeObject(ObjectOutputStream out) throws IOException { out.defaultWriteObject();}private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException{ ObjectInputStream.GetField fields = in.readFields(); id = (String) fields.get("id",null); balance = fields.get("balance",0); lastTxType = fields.get("lastTxType",'u'); lastTxAmount = fields.get("lastTxAmount",-1);}执行办法
BankAccount bb = loadAccount("/Users/buxuesong/Documents/svn_code/demo/account.dat");System.out.println(bb.getId() +" | " + bb.getBalance()+" | " +bb.getLastTxType()+" | "+bb.getLastTxAmount());输入10 | 750 | u | -1还能够针对某些字段不必须做序列化解决，须要通过transient润饰该字段，能够通过其它形式获取回来，这样节俭了序列化的工夫
具体如下
public class AccountGroup implements Serializable { private static final long serialVersionUID = 106962907155393149L; private Map<String, BankAccount> accountMap = new HashMap(); private transient int totalBalance; public int getTotalBalance(){ return totalBalance; } public void addAccount(BankAccount account){ totalBalance += account.getBalance(); accountMap.put(account.getId(), account); } private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { in.defaultReadObject(); for(BankAccount account: accountMap.values()) totalBalance += account.getBalance(); }}执行办法中的存储到流以及从流中取回的办法
private static void saveGroup(AccountGroup g, String fileName){ try(ObjectOutputStream os = new ObjectOutputStream(Files.newOutputStream(Paths.get(fileName)))){ os.writeObject(g); }catch(Exception e){ System.out.println(e.getSuppressed() +" | "+ e.getMessage()); }}private static AccountGroup loadGroup(String fileName){ AccountGroup g = null; try(ObjectInputStream oi = new ObjectInputStream(Files.newInputStream(Paths.get(fileName)))){ g = (AccountGroup) oi.readObject(); }catch(Exception e){ System.out.println(e.getSuppressed() +" | "+ e.getMessage()); } return g;}执行办法：
BankAccount acct1 = new BankAccount("1234", 500);BankAccount acct2 = new BankAccount("9866", 750);AccountGroup group = new AccountGroup();group.addAccount(acct1);group.addAccount(acct2);saveGroup(group, "/Users/buxuesong/Documents/svn_code/demo/group.dat");AccountGroup group2 = loadGroup("/Users/buxuesong/Documents/svn_code/demo/group.dat");System.out.println("group2.getTotalBalance:"+group2.getTotalBalance());输入
group2.getTotalBalance:1250其余序列化办法，实现Externalizable接口
void writeExternal(ObjectOutput out);void readExternal(ObjectInput in);