南京大学：《面向对象技术 OOT》课程教学资源（PPT课件讲稿）对象序列化和持久化 Object Serialization and Persistence

Obiect Serialization and Persistence 对象序列化和持久化 Institute of Computer Software 2021/1/28 Nanjing University

对象序列化和持久化 Object Serialization and Persistence 2021/1/28 Institute of Computer Software Nanjing University 1

最病 过摘要 口对象序列化 口对象持久化 a language level a Databases Hibernate Institute of Computer Software 2021/1/28 Nanjing University

摘要  对象序列化  对象持久化  Language level  Databases  Hibernate 2021/1/28 Institute of Computer Software Nanjing University 4

最病 ○ bject Serialization 5 口Why a What 口HoW Institute of Computer Software 2021/1/28 Nanjing University

Object Serialization  Why  What  How 2021/1/28 Institute of Computer Software Nanjing University 5

最病 A Java Object Serialization --Why 6 a Serialization is used for light weight persistence and for communication via sockets or remote method Invocation (RMI) Institute of Computer Software 2021/1/28 Nanjing University

Java Object Serialization -- Why  Serialization is used for lightweight persistence and for communication via sockets or Remote Method Invocation (RMI). 2021/1/28 Institute of Computer Software Nanjing University 6

最病 A Java Object Serialization --Example 7 public class Client public static void main( String args[) try(//Create a socket Socket soc new Socket(Inet Address getLocalHost(), 8020) ○ utput Strean。= soc. get Output Stream(); Object Output s new Object Output Stream(o); s write Object("Todays date"); swrite Object(new Date())i sclose();] catch(Exception e)t System. out. printIn(e get Message()) System. out. printIn (" Error during serialization") System. exit(1);] Institute of Computer Software 2021/1/28 Nanjing University

Java Object Serialization -- Example public class Client { public static void main(String args[]) { try { // Create a socket Socket soc = new Socket(InetAddress.getLocalHost(), 8020); OutputStream o = soc.getOutputStream(); ObjectOutput s = new ObjectOutputStream(o); s.writeObject("Today's date"); s.writeObject(new Date()); s.flush(); s.close(); } catch (Exception e) { System.out.println(e.getMessage()); System.out.println("Error during serialization"); System.exit(1); } } } 2021/1/28 Institute of Computer Software Nanjing University 7

最病 A Java Object Serialization --Example 8 public class Server public static void main(String args[)( Server Socket ser= null: Socket soc String str null; Date d null; ser= new Server Socket(8020); sOc= ser. accept( Input Stream o F soc. getlnput Stream(; Objectlnput s new ObjectInput Stream(o); tr=(String)s readobject(; d=(Date)s readObject( sclose( System. out. printIn(str ); System. out. printin( d); 3 catch(Exception e) System. out. printin(e getMessage () System. out printIn("Error during serialization") System. exit(1) Institute of Computer Software 2021/1/28 Nanjing University

Java Object Serialization -- Example public class Server { public static void main(String args[]) { ServerSocket ser = null; Socket soc = null; String str = null; Date d = null; try { ser = new ServerSocket(8020); soc = ser.accept(); InputStream o = soc.getInputStream(); ObjectInput s = new ObjectInputStream(o); str = (String) s.readObject(); d = (Date) s.readObject(); s.close(); System.out.println(str); System.out.println(d); } catch (Exception e) { System.out.println(e.getMessage()); System.out.println("Error during serialization"); System.exit(1); } } } 2021/1/28 Institute of Computer Software Nanjing University 8

最病 A Java Object Serialization --Example 9 a Writing to an object stream l/ Serialize today's date to a file FileOutputStream f new FileOutput Stream(tmp") Objectoutput s= new ObjectoutputStream(t) s writeobject( Today) s writeobject(new DateD) S flush Institute of Computer Software 2021/1/28 Nanjing University

Java Object Serialization -- Example  Writing to an object stream 2021/1/28 Institute of Computer Software Nanjing University 9 // Serialize today's date to a file. FileOutputStream f = new FileOutputStream("tmp"); ObjectOutput s = new ObjectOutputStream(f); s.writeObject("Today"); s.writeObject(new Date()); s.flush();

最病 A Java Object Serialization --Example n Reading from an object stream // Deserialize a string and date from a file FileInputStream in= new FileInputStream (" tmp") ObjectInputStream s= new objectInputstream(in) String today =(String)s. readobjecto Date date =(Date)s readobject( Institute of Computer Software 2021/1/28 Nanjing University

Java Object Serialization -- Example  Reading from an object stream 2021/1/28 Institute of Computer Software Nanjing University 10 // Deserialize a string and date from a file. FileInputStream in = new FileInputStream("tmp"); ObjectInputStream s = new ObjectInputStream(in); String today = (String)s.readObject(); Date date = (Date)s.readObject();

最病 A Java Object Serialization --What a Object Serialization extends the core Java Input Output classes with support for objects a Object Serialization supports the encoding of objects, and the objects reachable from them, into a stream of bytes; and it supports the complementary reconstruction of the object graph from the stream Institute of Computer Software 2021/1/28 Nanjing University

Java Object Serialization -- What  Object Serialization extends the core Java Input/Output classes with support for objects.  Object Serialization supports the encoding of objects, and the objects reachable from them, into a stream of bytes; and it supports the complementary reconstruction of the object graph from the stream. 2021/1/28 Institute of Computer Software Nanjing University 11

最病 A Java Object Serialization --Goal o Have a simple yet extensible mechanism a maintain the Java object type and safety properties in the serialized form n Be extensible to support marshaling and unmarshaling as needed for remote objects a Be extensible to support simple persistence of java objects n Require per class implementation only for customization. o Allow the object to define its external format Institute of Computer Software 2021/1/28 Nanjing University

Java Object Serialization -- Goal  Have a simple yet extensible mechanism.  Maintain the Java object type and safety properties in the serialized form.  Be extensible to support marshaling and unmarshaling as needed for remote objects.  Be extensible to support simple persistence of Java objects.  Require per class implementation only for customization.  Allow the object to define its external format. 2021/1/28 Institute of Computer Software Nanjing University 12