用jdbc实现对象与数据库表中记录的同步

java主要是面向对象的语言，因此，我们大多数操作的都是对象。我们如何将对象的信息存入到数据库中去了，其主要分为三步：
    1）：写出实体类的JavaBean
    2)：在数据库中建立与之对应的表记录
    3): 根据需求写出dao层
  （注：一般的，每一个对象都有唯一的一个OID(object ID),与数据库中表的ID一一对应。对象之间的关系在表之间中主要也反映为主外键的关系(假如对象在内存中没有OID，对象中表的跟新与查询变得相当的困难)。
  即：一旦一个对象在数据库表中有相应的记录，就会有相应的OID，这样的一个对象也就是一个持久化的对象，此时，如果跟新内存中该对象的值，提交之后就可以反映到数据库中去。如果一个对象在表中没有相应的记录，此时，该对象为一个临时对象，当该对象在很长一段时间没有被使用时就会被GC清理掉。)
以下是一个用JDBC实现对象存储的简单列子：

1：person的javabean

public class Person {
	
	private Integer id;//对象OID
	private String name;
	private String address;
	private String personId;
	
	public Person() {
		super();
	}

	public Person(String name, String address, String personId) {
		super();
		this.name = name;
		this.address = address;
		this.personId = personId;
	}

	public Integer getId() {
		return id;
	}

	public void setId(Integer cid) {
		this.id = cid;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getAddress() {
		return address;
	}

	public void setAddress(String address) {
		this.address = address;
	}

	public String getPersonId() {
		return personId;
	}

	public void setPersonId(String personId) {
		this.personId = personId;
	}
	
}

2：创建与之对应的表：

create sequence jdbc_person_sequence;//id通过该序列产生
create table person
(
id number(7) primary key,
name varchar2(20) not null,
address varchar2(30) not null,
personId varchar2(21) not null
);

3：用JDBC实现dao层：

import java.sql.*;
import com.UtilTool.*;
public class Dao_Person {
	
	/*
	 * function: insert a new personInfo into the person table 
	 * variable:insert a new personInfo
	 * */
	public void addPersonInfo(Person person)throws Exception{
		Connection connection=null;
		PreparedStatement pstm=null;
		try{
		person.setId(this.getIdSequence());//set the object ID from the method;
		 connection=ConnectTool.getConnection();//get current connection 
		 connection.setAutoCommit(false);//manual control the transaction commit
		String sql="insert into person(id,name,address,personId) values(?,?,?,?)";
		 pstm=connection.prepareStatement(sql);
		pstm.setInt(1, person.getId());
		pstm.setString(2, person.getName());
		pstm.setString(3, person.getAddress());
		pstm.setString(4, person.getPersonId());
		pstm.execute();
		connection.commit();
		}finally{
			ConnectTool.releasersc(null, pstm, null);//colse the Result and the pstm
		}
	}
	
	/*
	 * function:delete a person's information from table 'person'
	 * variable:the person you will delete
	 * */
	public void deletePersonInfo(Person person)throws Exception{
		Connection connection=null;
		PreparedStatement pstm=null;
		try{
		 connection=ConnectTool.getConnection();
		 connection.setAutoCommit(false);
		String sql="delete from person where id=?";
		 pstm=connection.prepareStatement(sql);
		pstm.setInt(1, person.getId());
		pstm.executeUpdate();
		connection.commit();
		}finally{
			ConnectTool.releasersc(null, pstm, null);
		}
		
	}
	
	/*
	 * function:modify the person's information in the table 'person'
	 * variable: person information you will update.
	 * */
	public void updatePersonInfo(Person person)throws Exception{
		Connection connection=null;
		PreparedStatement pstm=null;
		try{
		 connection=ConnectTool.getConnection();
		 connection.setAutoCommit(false);
		String sql="update person set name=?,address=?,personId=? where id=?";
		 pstm=connection.prepareStatement(sql);
		pstm.setString(1, person.getName());
		pstm.setString(2, person.getAddress());
		pstm.setString(3, person.getPersonId());
		pstm.setInt(4, person.getId());
		pstm.execute();
		connection.commit();
		}finally{
			ConnectTool.releasersc(null, pstm, null);
		}
		
		
	}
	/*
	 * function:get a person information by the persons's OId
	 * variable:person'OId you want to query.
	 * */
	public  Person  queryPersonInfo(Integer OId)throws Exception{
		Connection connection=null;
		PreparedStatement pstm=null;
		ResultSet rs=null;
		Person person=null;
		try{
		 connection=ConnectTool.getConnection();
		String sql="select * from person where id=?";
		 pstm=connection.prepareStatement(sql);
		pstm.setInt(1, OId);
		rs=pstm.executeQuery();
		if(rs.next()){
			person=new Person();
			person.setId(rs.getInt(1));
			person.setName(rs.getString(2));
			person.setAddress(rs.getString(3));
			person.setPersonId(rs.getString(4));
		}
		}finally{
			ConnectTool.releasersc(rs, pstm, null);
		}
		return person;
	}
	
	/*
	 * get the OId from the sequence jdbc_person_sequence
	 * */
	private Integer getIdSequence()throws Exception{
		Connection con=null;
		PreparedStatement pstm=null;
		ResultSet rs=null;
		Integer OId=null;
		try{
			con=ConnectTool.getConnection();
			String sql="select jdbc_person_sequence.nextVal from dual";
			pstm=con.prepareStatement(sql);
			rs=pstm.executeQuery();
			rs.next();
			OId=rs.getInt(1);
			
			
		}finally{
			ConnectTool.releasersc(rs, pstm, null);
		}
		return OId;
	}

}

以下是对上述代码的测试：

import java.sql.Connection;
import com.UtilTool.*;
public class Test {
	public static void main(String args[])throws Exception{
		Connection conn=ConnectTool.getConnection();
		Dao_Person dao=new Dao_Person();
		Person person=dao.queryPersonInfo(6);
		
		//dao.addPersonInfo(person);
		//dao.deletePersonInfo(person);
		person.setName("good morning");
		dao.updatePersonInfo(person);
		ConnectTool.releasersc(null, null, conn);
	}

}