简单管理系统的开发流程（基于XML）

摘要: 简单管理系统 开发流程 基于XML

简单管理系统的开发流程

1、定义好数据层

选择一个存储方式（XML）

创建users.xml

<?xml version="1.0" encoding="UTF-8"?>

<users>

</users>

2、创建DAO完成对用户对象的CRUD

Data Access Object -->DAO

DAO所做的事情是完成对用户对象的增删改查，常规的说，每一个对象都有一个DAO。

public class UserDao {
public static final String USER_XML = "users";
private Document ud;

public UserDao() {
ud = XMLUtil.getUserDocument();
}

private void write() {
XMLUtil.write2XML(ud, USER_XML);
}

private Element loadElementByUsername(String username) {
String path = "/users/user[username='"+username+"']";
Element e = (Element)ud.selectSingleNode(path);
return e;
}

private User element2User(Element e) {
User u = new User();
u.setNickname(e.elementText("nickname"));
u.setPassword(e.elementText("password"));
u.setUseranme(e.elementText("username"));
return u;
}

public void add(User user) {
if(user.getUseranme()==null||"".equals(user.getUseranme())) throw new ExpException("用户名不能为空");
User u = this.load(user.getUseranme());
if(u!=null) throw new ExpException("用户已经存在！不能继续添加");
Element e = ud.getRootElement().addElement("user");
e.addElement("username").addText(user.getUseranme());
e.addElement("password").addText(user.getPassword());
e.addElement("nickname").addText(user.getNickname());
write();
}

public void delete(String username) {
//1、获取根节点
Element root = ud.getRootElement();
//2、获取username的节点
Element e = loadElementByUsername(username);
root.remove(e);
write();
}

public void update(User user) {
//1、根据username获取节点
Element e = loadElementByUsername(user.getUseranme());
if(e==null) throw new ExpException("要更新的用户不存在");
//2、为这个节点修改数据
e.element("password").setText(user.getPassword());
e.element("nickname").setText(user.getNickname());
write();
}

public User load(String username) {
Element e = loadElementByUsername(username);
if(e==null) return null;
User u = element2User(e);
return u;
}

@SuppressWarnings("unchecked")
public List<User> list() {
String path = "/users/user";
List<Element> eles = ud.selectNodes(path);
List<User> users = new ArrayList<User>();
for(Element e:eles) {
users.add(element2User(e));
}
return users;
}

3、编写一个XML的工具类来完成对XML的操作

public class XMLUtil {
private static Document userDocument;

public static Document getUserDocument() {
//如果document存在直接返回
if(userDocument!=null) return userDocument;
//如果不存在就创建对象
try {
SAXReader reader = new SAXReader();
//System.out.println(XMLUtil.class.getResource(""));
//System.out.println(XMLUtil.class.getClassLoader().getResource(""));
userDocument = reader.read(XMLUtil.class.getClassLoader().getResourceAsStream("xml/users.xml"));
return userDocument;
} catch (DocumentException e) {
e.printStackTrace();
}
return null;
}

public static void write2XML(Document d,String name) {
XMLWriter out = null;
try {
String path = XMLUtil.class.getClassLoader().getResource("xml/"+name+".xml").getPath();
path = path.replace("bin", "src");
out = new XMLWriter(new FileWriter(path),OutputFormat.createPrettyPrint());
out.write(d);
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if(out!=null) out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

4、编写XML的单例模式

单例模式指的是所有的对象只有一个，这样可以提高访问的效率。

private static Document userDocument;

public static Document getUserDocument() {
//如果document存在直接返回
if(userDocument!=null) return userDocument;
//如果不存在就创建对象
try {
SAXReader reader = new SAXReader();
//System.out.println(XMLUtil.class.getResource(""));
//System.out.println(XMLUtil.class.getClassLoader().getResource(""));
userDocument = reader.read(XMLUtil.class.getClassLoader().getResourceAsStream("xml/users.xml"));
return userDocument;
} catch (DocumentException e) {
e.printStackTrace();
}
return null;
}