关于写入的原数据被修改的问题

当我输入下面输出语句（没有写UTF-8编码方式）时，运行代码（其他部分正常），我的XML文件原来的中文数据都会被修改？？？这不是只添加一个新的employee标签内容吗？怎么会影响到其他内容？当我把UTF-8代码添加后，一切都会正常。但是原始数据回不来了 ..TUT..

Writer writer = new OutputStreamWriter(new FileOutputStream(file));

代码如下：

package com.dom4j;

import java.io.FileOutputStream;

import java.io.OutputStreamWriter;

import java.io.Writer;

import org.dom4j.Document;

import org.dom4j.Element;

import org.dom4j.io.SAXReader;

public class HrWriter {

public void writeXml() {

String file = "E:\\javaworkspace\\xmltest\\src\\xmltest.xml";

SAXReader reader = new SAXReader();

try {

Document document = reader.read(file);

Element root = document.getRootElement();

Element employee = root.addElement("employee");

employee.addAttribute("no", "3333");

Element name = employee.addElement("name");

name.setText("王五");

Element age = employee.addElement("age");

age.setText("25");

employee.addElement("salary").setText("6434");

Element department = employee.addElement("department");

department.addElement("dname").setText("管理部");

department.addElement("address").setText("杏坛");

Writer writer = new OutputStreamWriter(new FileOutputStream(file), "UTF-8");

document.write(writer);

writer.close();

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

public static void main(String[] args) {

HrWriter hr = new HrWriter();

hr.writeXml();

}

}

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

<hr xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="xsdtest.xsd">

<employee no="324">

<name>张三</name>

<age>32</age>

<salary>3042</salary>

<department>

<dname>行政部</dname>

<address>大良</address>

</department>

</employee>

<employee no="325">

<name>李四</name>

<age>22</age>

<salary>4042</salary>

<department>

<dname>财务部</dname>

<address>容桂</address>

</department>

</employee>

</hr>