不使用持久層框架下的BsaeDao示例
本文介紹的是在不使用持久層框架的情況下，用Java反射寫的BaseDao，簡化Dao層的操作，讓Dao的實現層每個方法體只有一行。所有的Dao的實現類繼承BaseDao。 下面具體講如何使用BaseDao 。
- BaseDao代碼如下：
package dao;import java.lang.reflect.Field; import java.lang.reflect.Method; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.List;
import utils.DbHelper;
public class BaseDao { private Connection conn = null; private PreparedStatement ps = null; private ResultSet rs = null;
/** * 查詢符合條件的記錄數 * * @param sql * 要執行的sql語句 * @param args * 給sql語句中的？賦值的參數列表 * @return 符合條件的記錄數 */ public long getCount(String sql, Object... args) { conn = DbHelper.getConn(); try { ps = conn.prepareStatement(sql); for (int i = 0; i < args.length; i++) { ps.setObject(i + 1, args[i]); } rs = ps.executeQuery(); if (rs.next()) { return rs.getLong(1); } } catch (SQLException e) { e.printStackTrace(); } finally { DbHelper.closeConn(conn, ps, rs); } return 0L; } /** * 查詢實體對象的，并封裝到一個集合 * * @param <T> * 要查詢的對象的集合 * @param sql * 要執行的sql語句 * @param clazz * 要查詢的對象的類型 * @param args * 給sql語句中的？賦值的參數列表 * @return 要查詢的類的集合，無結果時返回null */ public <T> List<T> executeQuery(String sql, Class<T> clazz, Object... args) { conn = DbHelper.getConn(); List list = new ArrayList(); try { ps = conn.prepareStatement(sql); for (int i = 0; i < args.length; i++) { ps.setObject(i + 1, args[i]); } rs = ps.executeQuery(); Field[] fs = clazz.getDeclaredFields(); String[] colNames = new String[fs.length]; String[] rTypes = new String[fs.length]; Method[] methods = clazz.getMethods(); while (rs.next()) { for (int i = 0; i < fs.length; i++) { Field f = fs[i]; String colName = f.getName().substring(0, 1).toUpperCase() + f.getName().substring(1); colNames[i] = colName; String rType = f.getType().getSimpleName(); rTypes[i] = rType; } Object object = (T) clazz.newInstance(); for (int i = 0; i < colNames.length; i++) { String colName = colNames[i]; String methodName = "set" + colName; // 查找并調用對應的setter方法賦 for (Method m : methods) { if (methodName.equals((m.getName()))) { // 如果拋了參數不匹配異常，檢查JavaBean中該屬性類型，并添加else分支進行處理 if ("int".equals(rTypes[i]) || "Integer".equals(rTypes[i])) { m.invoke(object, rs.getInt(colName)); } else if ("Date".equals(rTypes[i])) { m.invoke(object, rs.getDate(colName)); } else if ("Timestamp".equals(rTypes[i])) { m.invoke(object, rs.getTimestamp(colName)); } else { m.invoke(object, rs.getObject(colName)); } break; } } } list.add(object); } return list; } catch (Exception e) { e.printStackTrace(); } finally { DbHelper.closeConn(conn, ps, rs); } return null; } /** * 以對象的形式保存或更新一個實體 * * @param sql * 要執行的sql語句 * @param object * 要保存或更新的實體對象 * @param args * 不需要賦值的列標組成的數組，例如sql語句 * "insert into tbl_user values(seq_user.nextval,?,?,?)"應為1 * @return 操作結果，1 成功，0 失敗 */ public int saveEntity(String sql, Object object, int... args) { conn = DbHelper.getConn(); try { ps = conn.prepareStatement(sql); Class c = object.getClass(); Field[] fields = object.getClass().getDeclaredFields(); int temp = 1;// 正賦值的？的下標，最大下標為args的長度 int colIndex = 1;// SQL語句中的當前字段下標 int t = 0;// args數組的下標 for (int j = 0; j < fields.length; j++) { Field field = fields[j];// 得到某個聲明屬性 String methodName = "get" + field.getName().substring(0, 1).toUpperCase() + field.getName().substring(1); Method method = c.getMethod(methodName);// 得到了當前類中的一個method String rType = field.getType().getSimpleName().toString(); if (t < args.length && colIndex == args[t]) { t++; } else if ("int".equals(rType) || "INTEGER".equals(rType)) { ps.setInt(temp++, (Integer) method.invoke(object)); } else { ps.setObject(temp++, method.invoke(object)); } colIndex++;// 更新索引下標 } return ps.executeUpdate(); } catch (Exception e) { e.printStackTrace(); } finally { DbHelper.closeConn(conn, ps, null); } return 0; } /** * 執行可變參數的SQL語句，進行保存、刪除或更新操作 * * @param sql * 要執行的sql語句，?的賦值順序必須與args數組的順序相同 * @param args * 要賦值的參數列表 * @return 操作結果，正數 成功，0 失敗 */ public int saveOrUpdate(String sql, Object... args) { conn = DbHelper.getConn(); try { ps = conn.prepareStatement(sql); for (int j = 0; j < args.length; j++) { ps.setObject(j + 1, args[j]); } return ps.executeUpdate(); } catch (Exception e) { e.printStackTrace(); } finally { DbHelper.closeConn(conn, ps, null); } return 0; }}</span> </pre></li>
- 連接數據庫的DbHelper工具類
package utils;import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement;
/**
- 數據庫工具類
- @author Jzl
*/ public class DbHelper {
/**
- 獲得一個數據庫連接
@return */ public static Connection getConn() { Connection conn = null; try {
Class.forName("oracle.jdbc.driver.OracleDriver"); String url = "jdbc:oracle:thin:@localhost:1521:orcl"; conn = DriverManager.getConnection(url, "scott", "tiger");} catch (Exception e) {
e.printStackTrace();} return conn; }
/**
- 關閉數據庫連接資源
- @param conn
- @param ps
- @param rs
*/
public static void closeConn(Connection conn, Statement ps, ResultSet rs) {
try {
} catch (Exception e) {if (rs != null) { rs.close(); rs = null; } if (ps != null) { ps.close(); ps = null; } if (conn != null) { conn.close(); conn = null; }
} }e.printStackTrace();
}</span> </pre></li>
- 接下來就可以測試BaseDao了。用于測試的User實體類：
package entity;import java.sql.Date;
/**
- 用于測試的JavaBean，符合JavaBea命名規范
@author Jzl / public class User { private int userId; private String userName; private String userPass; private Date lastDate;
/**
無參構造函數，用于反射new一個實例（必須有） */ public User() { }
public User(String userName, String userPass, Date lastDate) { super(); this.userName = userName; this.userPass = userPass; this.lastDate = lastDate; }
public int getUserId() { return userId; }
public void setUserId(int userId) { this.userId = userId; }
public String getUserName() { return userName; }
public void setUserName(String userName) { this.userName = userName; }
public String getUserPass() { return userPass; }
public void setUserPass(String userPass) { this.userPass = userPass; }
public Date getLastDate() { return lastDate; }
public void setLastDate(Date lastDate) { this.lastDate = lastDate; }
}</span> </pre></li>
- 用于測試的UserDao：
package dao;import java.util.List;
import entity.User;
/**
- 用于測試的UserDao
@author Jzl / public class UserDao extends BaseDao { public int addUser1(User user) {
return super.saveEntity( "insert into tbl_user values(seq_user.nextval,?,?,?)", user, 1);}
public int addUser2(User user) {
return super.saveOrUpdate( "insert into tbl_user values(seq_user.nextval,?,?,?)", user.getUserName(), user.getUserPass(), user.getLastDate());}
public int deleteUserById(int userId) {
return super .saveOrUpdate("delete from tbl_user where userId=?", userId);}
public int modUserById(int userId, User user) {
return super .saveOrUpdate( "update tbl_user set userName=?,userPass=?,lastDate=? where userId=?", user.getUserName(), user.getUserPass(), user.getLastDate(), userId);}
public User getUser(int userId) {
return super.executeQuery("select * from tbl_user where userId=?", User.class, userId).get(0);}
public List<User> getUserList() {
return super.executeQuery("select * from tbl_user", User.class);}
public long getUserCount(){
return super.getCount("select count(*) from tbl_user");} }</span> </pre></li>
- 用于測試UserDao的測試類：
package test;
import java.sql.Date; import java.util.List;
import org.junit.Test;
import dao.UserDao; import entity.User;
public class UserDaoTest { private UserDao userDao = new UserDao();
@Test public void testUserDao() { testAdd1(); testAdd2(); testDeleteById(); testModById(); System.out.println(testGetById().getUserName()); List<User> users = testGetList(); for (User user : users) { System.out.println(user.getUserId() + "==" + user.getUserName()); } System.out.println(testGetCount()); } public int testAdd1() { User user = new User("zs", "zs", new Date(System.currentTimeMillis())); return userDao.addUser1(user); } public int testAdd2() { User user = new User("zs", "zs", new Date(System.currentTimeMillis())); return userDao.addUser2(user); } public int testDeleteById() { return userDao.deleteUserById(104); } public User testGetById() { return userDao.getUser(104); } public int testModById() { User user = new User("ls", "ls", new Date(System.currentTimeMillis())); return userDao.modUserById(104, user); } public List<User> testGetList() { return userDao.getUserList(); } public long testGetCount() { return userDao.getUserCount(); }}</span> </pre></li>
- 創建用于測試的數據庫表：
</ol>這里用Oracle數據庫作測試，建表語句如下，
--創建測試表 create table tbl_user ( userId number(8) primary key not null, userName varchar2(20), userPass varchar2(20), lastDate Date );
create sequence seq_user;</pre>
來自：http://z2009zxiaolong.iteye.com/blog/1561221 - 連接數據庫的DbHelper工具類