用xml模拟数据库,并实现基本的CURD操作 - 黑马程序员技术交流社区

package com.sunsheng.dao.inter;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.List;
import com.sunsheng.Exception.IdNotFoundException;
public interface CURD {
/**
* 把javabean写入到xml文件中
* @param record
* @throws IOException
* @throws IllegalAccessException
* @throws InvocationTargetException
* @throws NoSuchMethodException
*/
void create(Object record) throws IOException, IllegalAccessException, InvocationTargetException, NoSuchMethodException;
/**
* 根据指定的id修改xml数据
* @param id
* @param record
* @throws IOException
* @throws IllegalAccessException
* @throws InvocationTargetException
* @throws NoSuchMethodException
*/
void update(int id, Object record)
throws IOException,
IllegalAccessException,
InvocationTargetException,
NoSuchMethodException;
/**
* 获得所有的xml元素
* @return 返回值是所有bean的list集合
* @throws IllegalAccessException
* @throws InvocationTargetException
* @throws InstantiationException
*/
List read()
throws IllegalAccessException,
InvocationTargetException, InstantiationException;
/**
* 删除指定id的元素
* @param id
* @throws IdNotFoundException
* @throws IOException
*/
void delete(int id)
throws IdNotFoundException,
IOException;
}

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package com.sunsheng.dao.imp;
import java.beans.PropertyDescriptor;
import java.io.*;
import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.apache.commons.beanutils.BeanUtils;
import org.apache.commons.beanutils.PropertyUtils;
import org.dom4j.*;
import org.dom4j.io.*;
import com.sunsheng.Exception.IdNotFoundException;
import com.sunsheng.dao.inter.CURD;
import com.sunsheng.domain.Person;
public class XMLImp implements CURD {
private Document document;
private Class clazz;
private static XMLImp instance = new XMLImp();
private XMLImp() {
super();
}
public static XMLImp getInstance() {
return instance;
}
/**
* 初始化document对象,如果xml不存在,会自动创建一个,根节点默认是records
* @param clazz 要转换成xml文件的bean的Class
* @throws DocumentException
* @throws IOException
*/
public void init(Class clazz) throws DocumentException, IOException {
init(clazz, "records");
}
/**
*
* @param clazz
* @param root 手动设置根节点的名字
* @throws DocumentException
* @throws IOException
*/
public void init(Class clazz, String root) throws DocumentException, IOException {
this.clazz = clazz;
SAXReader reader = new SAXReader();
File file = new File("abc.xml");
//判断文件是否存在
if (!file.exists()) {
//不存在的话,创建一个空文件,留给xml2File方法使用
file.createNewFile();
//创建一个document对象,往这个对象里面添加一个根元素.
document = DocumentHelper.createDocument();
document.addElement(root);
} else
//存在就直接读文件
document = reader.read(file);
}
@Override
public void create(Object record) throws IOException,
IllegalAccessException, InvocationTargetException,
NoSuchMethodException {
// 获得xml文件的根节点
Element root = document.getRootElement();
// 根据record得到标签的名字
String tagName = getTagName();
// 得到record的id属性
String value = (BeanUtils.getProperty(record, "id"));
// 创建一个element,并添加到root下面,设置一个属性id
Element element = root.addElement(tagName).addAttribute("id", value);
// 在element下面创建多个子元素用来保存record的每一个属性
PropertyDescriptor[] pds = PropertyUtils.getPropertyDescriptors(record);
for (PropertyDescriptor pd : pds) {
// 得到属性名,作为子标签名字.
String childTagname = pd.getName();
// 继承自Object类的class属性不存到xml中
if ("class".equals(childTagname))
continue;
// 得到该属性get方法返回值作为标签的text属性
String childTagValue = pd.getReadMethod().invoke(record, null)
.toString();
// 用得到的属性名和值添加一个子元素
element.addElement(childTagname).addText(childTagValue);
}
// 保存xml到文件中
xml2File();
}
@Override
public void update(int id, Object record) throws IOException,
IllegalAccessException, InvocationTargetException,
NoSuchMethodException {
Person person = (Person) record;
Element element = (Element) document.selectSingleNode("//person[@id="
+ id + "]");
for (Iterator iterator = element.elementIterator(); iterator.hasNext();) {
Element e = (Element) iterator.next();
// 获得标签的名字
String name = e.getName();
// 通过标签名字得到bean的属性值
String text = BeanUtils.getProperty(person, name);
// 修改标签的text值
e.setText(text);
}
xml2File();
}
@Override
public List read() throws IllegalAccessException,
InvocationTargetException, InstantiationException {
List beans = new ArrayList();
List list = document.selectNodes("//" + getTagName());
// System.out.println(list);
for (Iterator iterator = list.iterator(); iterator.hasNext();) {
Object bean = clazz.newInstance();
Element e = (Element) iterator.next();
// 得到元素的所有属性对象
List<Attribute> atts = e.attributes();
for (Attribute att : atts) {
// 遍历每一个属性,按属性名和值设置到对应的bean中
BeanUtils.setProperty(bean, att.getName(), att.getValue());
}
Iterator it = e.elementIterator();
while (it.hasNext()) {
Element value = (Element) it.next();
BeanUtils.setProperty(bean, value.getName(), value.getText());
}
beans.add(bean);
}
return beans;
}
@Override
public void delete(int id) throws IdNotFoundException, IOException {
// 获得xml文件的根节点
Node node = document.selectSingleNode("//" + getTagName() + "[@id="
+ id + "]");
if (node != null) {
node.detach();
xml2File();
} else {
throw new IdNotFoundException("您要删除的ID不存在");
}
}
private void xml2File() throws IOException {
OutputFormat format = OutputFormat.createPrettyPrint();
XMLWriter writer;
writer = new XMLWriter(new FileWriter("abc.xml"), format);
writer.write(document);
writer.close();
}
private String getTagName() {
String beanName = clazz.getName();
String tagName = beanName.substring(beanName.lastIndexOf(".") + 1)
.toLowerCase();
return tagName;
}
}

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