VO(value object) 值對象
通常用于業務層之間的數據傳遞，和PO一樣也是僅僅包含數據而已。但應是抽象出的業務對象,可以和表對應,也可以不,這根據業務的需要.個人覺得同DTO(數據傳輸對象),在web上傳遞。
對于數據庫而言，每一個VO對象可以表示出一張表中的一行記錄，此類的名稱要與表的名稱一致。
BO(business object) 業務對象
從業務模型的角度看,見UML元件領域模型中的領域對象。封裝業務邏輯的java對象,通過調用DAO方法,結合PO,VO進行業務操作。
PO(persistant object) 持久對象
在o/r映射的時候出現的概念，如果沒有o/r映射，沒有這個概念存在了。通常對應數據模型(數據庫),本身還有部分業務邏輯的處理。可以看成是與數據庫中的表相映射的java對象。最簡單的PO就是對應數據庫中某個表中的一條記錄，多個記錄可以用PO的集合。PO中應該不包含任何對數據庫的操作。
DAO(data access object )數據訪問對象
此對象用于訪問數據庫。通常和PO結合使用，DAO中包含了各種數據庫的操作方法。通過它的方法,結合PO對數據庫進行相關的操作。
建議命名規則：I表名DAO，如IUserDAO
方法命名規則：更新數據庫 doXxx()
查詢數據庫 findXxx()或getXxx()
POJO(plain ordinary java object) 簡單無規則java對象。
DAO設計模式
實現類
實現DAO接口的具體方法，如實現具體CRUD操作。但沒有具體的數據庫的連接、打開、關閉，具體的操作可以放在代理（Proxy）中，因為這些操作與具體業務無關。
代理(Proxy)
實現具體的操作及數據庫的連接開關，并且實現其具體的主題類。
工廠模式(Factory)
有接口就必須有工廠類進行耦合。
注意：在Java開發web頁面中，永遠不導入java.sql包，只能導入java.util.*和vo包。
下面給出一個具體的例子的代碼(來自mldn李新華的教程)：
VO:(oracle.vo)
1
package org.lxh.oracle.vo;
2
3import java.util.Date;
4
5
public class Emp 
{
6
private int empno ;
7 private String ename ;
8 private String job ;
9 private Date hiredate ;
10 private float sal ;
11 private float comm ;
12 private String photo ;
13
public float getComm() {
14 return comm;
15
}
16 public void setComm(float comm) {
17 this.comm = comm;
18 }
19 public int getEmpno() {
20 return empno;
21 }
22 public void setEmpno(int empno) {
23 this.empno = empno;
24 }
25 public Date getHiredate() {
26 return hiredate;
27 }
28 public void setHiredate(Date hiredate) {
29 this.hiredate = hiredate;
30 }
31 public String getJob() {
32 return job;
33 }
34 public void setJob(String job) {
35 this.job = job;
36 }
37 public String getPhoto() {
38 return photo;
39 }
40 public void setPhoto(String photo) {
41 this.photo = photo;
42 }
43 public float getSal() {
44 return sal;
45 }
46 public void setSal(float sal) {
47 this.sal = sal;
48 }
49 public String getEname() {
50 return ename;
51 }
52 public void setEname(String ename) {
53 this.ename = ename;
54 }
55
}
DB的連接及開關
1package org.lxh.oracle.dbc;
2
3import java.sql.* ;
4public class DataBaseConnection{
5 public static final String DBDRIVER =
6
7"oracle.jdbc.driver.OracleDriver" ;
8 public static final String DBURL =
9
10"jdbc:oracle:thin:@localhost:1521:MLDN" ;
11 public static final String DBUSER =
12
13"scott" ;
14 public static final String DBPASS =
15
16"tiger" ;
17 private Connection conn = null ;
18 public DataBaseConnection(){
19 try{
20 Class.forName(DBDRIVER)
21
22;
23 conn =
24
25DriverManager.getConnection
26
27(DBURL,DBUSER,DBPASS) ;
28 }catch(Exception e){
29 e.printStackTrace() ;
30 }
31 }
32 public Connection getConnection(){
33 return this.conn ;
34 }
35 public void close(){
36 if(this.conn!=null){
37 try{
38
39
40this.conn.close() ;
41 }catch(Exception e){}
42 }
43 }
44};
45
DAO類：
1package org.lxh.oracle.dao;
2
3import java.util.List;
4
5import org.lxh.oracle.vo.Emp;
6
7public interface IEmpDAO {
8 public boolean doCreate(Emp emp) throws Exception;
9
10 public boolean doUpdate(Emp emp) throws Exception;
11
12 public boolean doDelete(int empno) throws Exception;
13
14 public Emp findById(int empno) throws Exception;
15
16 public List findAll(int currentPage,int lineSize,String keyWord) throws Exception ;
17
18 public int getAllCount(String keyWord) throws Exception ;
19}
Implements實現類
1package org.lxh.oracle.dao.impl;
2
3import java.sql.Connection;
4import java.sql.PreparedStatement;
5import java.sql.ResultSet;
6import java.util.ArrayList;
7import java.util.List;
8
9import org.lxh.oracle.dao.IEmpDAO;
10import org.lxh.oracle.vo.Emp;
11
12public class IEmpDAOImpl implements IEmpDAO {
13 private Connection conn = null; // 如果要想完成數據庫操作則肯定需要數據庫連接對象
14 public IEmpDAOImpl(Connection conn){
15 this.conn = conn ; // 由外部實例化時傳遞連接
16 }
17 public boolean doCreate(Emp emp) throws Exception {
18 boolean flag = false;
19 PreparedStatement pstmt = null;
20 String sql = "INSERT INTO emp(empno,ename,job,hiredate,sal,comm,photo) VALUES (?,?,?,?,?,?,?)";
21 try {
22 pstmt = this.conn.prepareStatement(sql);
23 pstmt.setInt(1, emp.getEmpno());
24 pstmt.setString(2, emp.getEname());
25 pstmt.setString(3, emp.getJob());
26 pstmt.setDate(4, new java.sql.Date(emp.getHiredate().getTime()));
27 pstmt.setFloat(5, emp.getSal());
28 pstmt.setFloat(6, emp.getComm());
29 pstmt.setString(7, emp.getPhoto());
30 int count = pstmt.executeUpdate(); // 執行更新，返回更新的記錄數
31 if (count > 0) {
32 flag = true;
33 }
34 } catch (Exception e) {
35 throw e;
36 } finally {
37 try {
38 pstmt.close();
39 } catch (Exception e) {
40 }
41 }
42 return flag;
43 }
44
45 public boolean doDelete(int empno) throws Exception {
46 boolean flag = false;
47 PreparedStatement pstmt = null;
48 String sql = "DELETE FROM emp WHERE empno=?";
49 try {
50 pstmt = this.conn.prepareStatement(sql);
51 pstmt.setInt(1, empno);
52 int count = pstmt.executeUpdate(); // 執行更新，返回更新的記錄數
53 if (count > 0) {
54 flag = true;
55 }
56 } catch (Exception e) {
57 throw e;
58 } finally {
59 try {
60 pstmt.close();
61 } catch (Exception e) {
62 }
63 }
64 return flag;
65 }
66
67 public boolean doUpdate(Emp emp) throws Exception {
68 boolean flag = false;
69 PreparedStatement pstmt = null;
70 String sql = "UPDATE emp SET ename=?,job=?,hiredate=?,sal=?,comm=?,photo=? WHERE empno=?";
71 try {
72 pstmt = this.conn.prepareStatement(sql);
73 pstmt.setString(1, emp.getEname());
74 pstmt.setString(2, emp.getJob());
75 pstmt.setDate(3, new java.sql.Date(emp.getHiredate().getTime()));
76 pstmt.setFloat(4, emp.getSal());
77 pstmt.setFloat(5, emp.getComm());
78 pstmt.setString(6, emp.getPhoto());
79 pstmt.setInt(7, emp.getEmpno());
80 int count = pstmt.executeUpdate(); // 執行更新，返回更新的記錄數
81 if (count > 0) {
82 flag = true;
83 }
84 } catch (Exception e) {
85 throw e;
86 } finally {
87 try {
88 pstmt.close();
89 } catch (Exception e) {
90 }
91 }
92 return flag;
93 }
94
95 public List findAll(int currentPage, int lineSize, String keyWord)
96 throws Exception {
97 List allEmp = new ArrayList();
98 PreparedStatement pstmt = null;
99 String sql = "SELECT temp.* FROM "
100 + "(SELECT empno,ename,job,hiredate,sal,comm,photo,ROWNUM rn "
101 + " FROM emp "
102 + " WHERE (empno LIKE upper(?) OR ename LIKE upper(?) OR job LIKE upper(?) "
103 + "OR to_char(hiredate,'yyyy') LIKE upper(?) OR to_char(hiredate,'mm') LIKE upper(?)"
104 + " OR to_char(hiredate,'dd') LIKE upper(?) OR sal LIKE upper(?) OR comm LIKE upper(?)) "
105 + " AND ROWNUM<=" + (currentPage * lineSize)
106 + ") temp WHERE temp.rn>" + (currentPage - 1) * lineSize;
107 try {
108 pstmt = this.conn.prepareStatement(sql);
109 pstmt.setString(1, "%" + keyWord + "%");
110 pstmt.setString(2, "%" + keyWord + "%");
111 pstmt.setString(3, "%" + keyWord + "%");
112 pstmt.setString(4, "%" + keyWord + "%");
113 pstmt.setString(5, "%" + keyWord + "%");
114 pstmt.setString(6, "%" + keyWord + "%");
115 pstmt.setString(7, "%" + keyWord + "%");
116 pstmt.setString(8, "%" + keyWord + "%");
117 ResultSet rs = pstmt.executeQuery();
118 Emp emp = null;
119 while (rs.next()) {
120 emp = new Emp();
121 emp.setEmpno(rs.getInt(1));
122 emp.setEname(rs.getString(2));
123 emp.setJob(rs.getString(3));
124 emp.setHiredate(rs.getDate(4));
125 emp.setSal(rs.getFloat(5));
126 emp.setComm(rs.getFloat(6));
127 emp.setPhoto(rs.getString(7));
128 allEmp.add(emp);
129 }
130 rs.close();
131 } catch (Exception e) {
132 throw e;
133 } finally {
134 try {
135 pstmt.close();
136 } catch (Exception e) {
137 }
138 }
139 return allEmp;
140 }
141
142 public Emp findById(int empno) throws Exception {
143 Emp emp = null;
144 PreparedStatement pstmt = null;
145 String sql = "SELECT empno,ename,job,hiredate,sal,comm,photo FROM emp WHERE empno=?";
146 try {
147 pstmt = this.conn.prepareStatement(sql);
148 pstmt.setInt(1, empno);
149 ResultSet rs = pstmt.executeQuery();
150 if (rs.next()) { // 表示已經查找到了
151 emp = new Emp();
152 emp.setEmpno(rs.getInt(1));
153 emp.setEname(rs.getString(2));
154 emp.setJob(rs.getString(3));
155 emp.setHiredate(rs.getDate(4));
156 emp.setSal(rs.getFloat(5));
157 emp.setComm(rs.getFloat(6));
158 emp.setPhoto(rs.getString(7));
159 }
160 rs.close();
161 } catch (Exception e) {
162 throw e;
163 } finally {
164 try {
165 pstmt.close();
166 } catch (Exception e) {
167 }
168 }
169 return emp;
170 }
171
172 public int getAllCount(String keyWord) throws Exception {
173 int count = 0;
174 PreparedStatement pstmt = null;
175 String sql = "SELECT COUNT(empno) FROM emp "
176 + " WHERE empno LIKE upper(?) OR ename LIKE upper(?) OR job LIKE upper(?) "
177 + " OR to_char(hiredate,'yyyy') LIKE upper(?) OR to_char(hiredate,'mm') LIKE upper(?) "
178 + " OR to_char(hiredate,'dd') LIKE upper(?) OR sal LIKE upper(?) OR comm LIKE upper(?)";
179 try {
180 pstmt = this.conn.prepareStatement(sql);
181 pstmt.setString(1,"%"+keyWord+"%") ;
182 pstmt.setString(2,"%"+keyWord+"%") ;
183 pstmt.setString(3,"%"+keyWord+"%") ;
184 pstmt.setString(4,"%"+keyWord+"%") ;
185 pstmt.setString(5,"%"+keyWord+"%") ;
186 pstmt.setString(6,"%"+keyWord+"%") ;
187 pstmt.setString(7,"%"+keyWord+"%") ;
188 pstmt.setString(8,"%"+keyWord+"%") ;
189 ResultSet rs = pstmt.executeQuery();
190 if (rs.next()) { // 表示已經查找到了
191 count = rs.getInt(1) ;
192 }
193 rs.close();
194 } catch (Exception e) {
195 throw e;
196 } finally {
197 try {
198 pstmt.close();
199 } catch (Exception e) {
200 }
201 }
202 return count;
203 }
204
205}
206
Proxy類
1package org.lxh.oracle.dao.proxy;
2
3import java.util.List;
4
5import org.lxh.oracle.dao.IEmpDAO;
6import org.lxh.oracle.dao.impl.IEmpDAOImpl;
7import org.lxh.oracle.dbc.DataBaseConnection;
8import org.lxh.oracle.vo.Emp;
9
10public class IEmpDAOProxy implements IEmpDAO {
11 private DataBaseConnection dbc = null ;
12 private IEmpDAO dao = null ;
13 private int count = 0 ;
14 public IEmpDAOProxy(){
15 this.dbc = new DataBaseConnection() ; // 在代理類中完成數據庫連接對象的實例化
16 this.dao = new IEmpDAOImpl(this.dbc.getConnection()) ;
17 }
18 public boolean doCreate(Emp emp) throws Exception {
19 boolean flag = false ;
20 try{
21 if(this.dao.findById(emp.getEmpno())==null){
22 flag = this.dao.doCreate(emp) ; // 調用真實主題實現類
23 }
24 }catch(Exception e){
25 throw e ;
26 }finally{
27 this.dbc.close() ;
28 }
29 return flag;
30 }
31
32 public boolean doDelete(int empno) throws Exception {
33 boolean flag = false ;
34 try{
35 flag = this.dao.doDelete(empno) ; // 調用真實主題實現類
36 }catch(Exception e){
37 throw e ;
38 }finally{
39 this.dbc.close() ;
40 }
41 return flag;
42 }
43
44 public boolean doUpdate(Emp emp) throws Exception {
45 boolean flag = false ;
46 try{
47 flag = this.dao.doUpdate(emp) ; // 調用真實主題實現類
48 }catch(Exception e){
49 throw e ;
50 }finally{
51 this.dbc.close() ;
52 }
53 return flag;
54 }
55
56 public List findAll(int currentPage, int lineSize, String keyWord)
57 throws Exception {
58 List all = null ;
59 try{
60 all = this.dao.findAll(currentPage, lineSize, keyWord) ;
61 this.count = this.dao.getAllCount(keyWord) ; // 查全部記錄的時候把全部的記錄數也查出來
62 }catch(Exception e){
63 throw e ;
64 }finally{
65 this.dbc.close() ;
66 }
67 return all;
68 }
69
70 public Emp findById(int empno) throws Exception {
71 Emp emp = null ;
72 try{
73 emp = this.dao.findById(empno) ;
74 }catch(Exception e){
75 throw e ;
76 }finally{
77 this.dbc.close() ;
78 }
79 return emp;
80 }
81
82 public int getAllCount(String keyWord) throws Exception {
83 return this.count;
84 }
85
86}
87
工廠Factory類
1package org.lxh.oracle.dao.factory;
2
3import org.lxh.oracle.dao.IEmpDAO;
4import org.lxh.oracle.dao.proxy.IEmpDAOProxy;
5
6public class DAOFactory {
7 public static IEmpDAO getIEmpDAOInstance(){
8 return new IEmpDAOProxy() ;
9 }
10}