结合Java反射用简单工厂模式改进抽象工厂模式

前一篇简单介绍了抽象工厂模式，结合Java的反射机制，可以用简单工厂模式来改进抽象工厂模式，减少类的数量，增加可维护性。UML图如下：

去除IFactory、SqlserverFactory和AccessFactory三个工厂类，取而代之的是DataAccess类，用一个简单工厂模式来实现。

代码示例：

1. 两个表User和Department的实体类

public class User {private int id;private String userName;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getUserName() {return userName;}public void setUserName(String userName) {this.userName = userName;}public User(int id, String userName) {super();this.id = id;this.userName = userName;}public User() {super();// TODO Auto-generated constructor stub}@Overridepublic String toString() {return "User [id=" + id + ", userName=" + userName + "]";}}

public class Department {private int id;private String deptName;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getDeptName() {return deptName;}public void setDeptName(String deptName) {this.deptName = deptName;}public Department() {super();// TODO Auto-generated constructor stub}public Department(int id, String deptName) {super();this.id = id;this.deptName = deptName;}@Overridepublic String toString() {return "Department [deptName=" + deptName + ", id=" + id + "]";}}

2. 两个表操作的接口

public interface IUserDao {abstract void insert(User user);abstract User select(int id);}

public interface IDepartmentDao {abstract void insert(Department dept);abstract Department select(int id);}

3. IUserDao的MySQL实现和Oracle实现

public class UserMysqlImpl implements IUserDao {@Overridepublic void insert(User user) {// TODO Auto-generated method stubSystem.out.println("User: MySQL实现插入一条记录："+user.toString());}@Overridepublic User select(int id) {// TODO Auto-generated method stubSystem.out.println("User: MySQL实现查询 ：id = "+id);return null;}}

public class UserOracleImpl implements IUserDao {@Overridepublic void insert(User user) {// TODO Auto-generated method stubSystem.out.println("User: Oracle实现插入一条记录："+user.toString());}@Overridepublic User select(int id) {// TODO Auto-generated method stubSystem.out.println("User: Oracle实现查询 ：id = "+id);return null;}}

4. IDepartmentDao的Mysql实现和oracle实现

public class DepartmentMySqlImpl implements IDepartmentDao {@Overridepublic void insert(Department dept) {// TODO Auto-generated method stubSystem.out.println("Department: MySQL实现插入一条记录." + dept.toString());}@Overridepublic Department select(int id) {// TODO Auto-generated method stubSystem.out.println("Department: MySQL查询记录 id = " + id);return null;}}

public class DepartmentOracleImpl implements IDepartmentDao{@Overridepublic void insert(Department dept) {// TODO Auto-generated method stubSystem.out.println("Department: Oracle实现插入一条记录." + dept.toString());}@Overridepublic Department select(int id) {// TODO Auto-generated method stubSystem.out.println("Department: Oracle实现查询一条记录 id = " + id);return null;}}

5.DataAccess类

public class DataAccess {private String db;public IUserDao createUserDao() throws ClassNotFoundException, InstantiationException, IllegalAccessException{if(db != null && !db.equals("")){//拼接字符串，注意类名包含包名String className = "com.design.abstractFactory.product.User" + db +"Impl";//获取以className字符串为名的类Class<IUserDao> userDaoImplClass = (Class<IUserDao>) Class.forName(className);//返回类的实例return userDaoImplClass.newInstance();}return null;}public IDepartmentDao createDepatDao() throws ClassNotFoundException,InstantiationException, IllegalAccessException{if(db != null && !db.equals("")){//拼接字符串，注意类名包括包名String className = "com.design.abstractFactory.product.Department" + db +"Impl";//获取以className字符串为名的类Class<IDepartmentDao> deptDaoImplClass = (Class<IDepartmentDao>) Class.forName(className);//返回类的实例return deptDaoImplClass.newInstance();}return null;}public String getDb() {return db;}public void setDb(String db) {this.db = db;}}

6. client端

public class abstractFactoryTest {@Testpublic void testDataAccess() throws IOException, ClassNotFoundException, InstantiationException, IllegalAccessException{Properties proper = new Properties();InputStream is = this.getClass().getClassLoader().getResourceAsStream("DB.properties");proper.load(is);String db = proper.getProperty("db");DataAccess dataAcc = new DataAccess();dataAcc.setDb(db);IUserDao userDao =  dataAcc.createUserDao();IDepartmentDao deptDao = dataAcc.createDepatDao();User user = new User(1, "pathfiner");Department dept = new Department(1, "aaa");userDao.insert(user);deptDao.select(1);}}

DB.properties

db=MySql