java读写xml文件

有两种方法一种是利用jdk自带的（里面的javax.xml.parsers包和org.w3c.dom包），另一种是利用dom4j架包，相比下我觉的dom4j更好，更加明了；jdk自带的那种利用节点链的数据结构，我觉的他更加复杂化了问题，刚看可能摸不着头脑。废话不多说了，来读下下面的xml

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

<database>
<use_sql>Oracle</use_sql>
<dialect>
<MySQL>org.hibernate.dialect.MySQLDialect</MySQL>
<Ms_SQL_Server>org.hibernate.dialect.SQLServerDialect</Ms_SQL_Server>
<Oracle>org.hibernate.dialect.Oracle10gDialect</Oracle>
</dialect>
<driver>oracle.jdbc.driver.OracleDriver</driver>

<url>jdbc:oracle:thin:@127.0.0.1:1521:wait</url>
<user>system</user>
<password>123456</password>
</database>

<program>
<paging>20</paging>
</program>

</setting>

1、先来jdk自带的那种：

(1)读文件：

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = dbf.newDocumentBuilder();
Document xmlDoc = builder.parse("setting.xml");
NodeList nodeList = xmlDoc.getElementsByTagName("database");
NodeList databaseList = nodeList.item(0).getChildNodes();
for(int i = 0, len = databaseList.getLength(); i < len; i++)
{
Node childNode = databaseList.item(i);
if (childNode instanceof Element)
{
String childName = childNode.getNodeName();
if("use_sql".equals(childName))
useSql = childNode.getFirstChild().getNodeValue();
else if("dialect".equals(childName))
{
NodeList dialectNodeList = childNode.getChildNodes();
for(int j = 0, len2 = dialectNodeList.getLength(); j < len2; j++)
{
Node dialectNode = dialectNodeList.item(j);
if(dialectNode instanceof Element)
{
String dialectName = dialectNode.getNodeName();
String dialectValue = dialectNode.getFirstChild().getNodeValue();
dialect.put(dialectName, dialectValue);
}
}

}
else if("driver".equals(childName))
driver = childNode.getFirstChild().getNodeValue();
else if("url".equals(childName))
url = childNode.getFirstChild().getNodeValue();
else if("user".equals(childName))
user = childNode.getFirstChild().getNodeValue();
else if("password".equals(childName))
password = childNode.getFirstChild().getNodeValue();
}
}

nodeList = xmlDoc.getElementsByTagName("program");
databaseList = nodeList.item(0).getChildNodes();
for(int i = 0, len = databaseList.getLength(); i < len; i++)
{
Node childNode = databaseList.item(i);
if (childNode instanceof Element)
{
String childName = childNode.getNodeName();
if("paging".equals(childName))
{
paging = childNode.getFirstChild().getNodeValue();
break;
}
}
}

(2)写文件

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = dbf.newDocumentBuilder();
Document xmlDoc = builder.parse("setting.xml");
NodeList nodeList = xmlDoc.getElementsByTagName("database");
NodeList databaseList = nodeList.item(0).getChildNodes();
for(int i = 0, len = databaseList.getLength(); i < len; i++)
{
Node childNode = databaseList.item(i);
if (childNode instanceof Element)
{
String childName = childNode.getNodeName();
if("use_sql".equals(childName))
childNode.getFirstChild().setNodeValue(useSql);
else if("driver".equals(childName))
childNode.getFirstChild().setNodeValue(getDriver(useSql));
else if("url".equals(childName))
childNode.getFirstChild().setNodeValue(url);
else if("user".equals(childName))
childNode.getFirstChild().setNodeValue(user);
else if("password".equals(childName))
childNode.getFirstChild().setNodeValue(password);
}
}

nodeList = xmlDoc.getElementsByTagName("program");
databaseList = nodeList.item(0).getChildNodes();
for(int i = 0, len = databaseList.getLength(); i < len; i++)
{
Node childNode = databaseList.item(i);
if (childNode instanceof Element)
{
String childName = childNode.getNodeName();
if("paging".equals(childName))
{
childNode.getFirstChild().setNodeValue(paging);
break;
}
}
}

//真正持久化的代码
TransformerFactory factory = TransformerFactory.newInstance();
Transformer t = factory.newTransformer();
t.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
DOMSource source =  new DOMSource(xmlDoc);
StreamResult result = new StreamResult(new File("setting.xml"));
t.transform(source, result);

2、利用dom4j：

(1)读文件

SAXReader reader = new SAXReader();
Document xmlDoc = reader.read(new File("setting.xml"));
Element root = xmlDoc.getRootElement();
List<Element> properties = root.elements("database");
for(Element property : properties)
{
Element useSqlE = property.element("use_sql");
useSql = useSqlE.getText();

Element dialectE = property.element("dialect");
for(Iterator<Element> iter = dialectE.elements().iterator(); iter.hasNext();)
{
Element e = iter.next();
dialect.put(e.getName(), e.getText());
}

Element driverE = property.element("driver");
driver = driverE.getText();

Element urlE = property.element("url");
url = urlE.getText();

Element userE = property.element("user");
user = userE.getText();

Element passwordE = property.element("password");
password = passwordE.getText();
}

properties = root.elements("program");
for(Element property : properties)
{
Element pagingE = property.element("paging");
paging = pagingE.getText();
String name = property.getName();

}

(2)写文件:

SAXReader reader = new RAXReader();
<span style="white-space:pre">			</span>Document xmlDoc = reader.read(new File("setting.xml"));
Element root = xmlDoc.getRootElement();
List<Element> properties = root.elements("database");
for(Element property : properties)
{
Element useSqlE = property.element("use_sql");
useSqlE.setText(useSql);

Element driverE = property.element("driver");
driverE.setText(getDriver(useSql));

Element urlE = property.element("url");
urlE.setText(url);

Element userE = property.element("user");
userE.setText(user);

Element passwordE = property.element("password");
passwordE.setText(password);

}

properties = root.elements("program");
for(Element property : properties)
{
String name = property.getName();
if("paging".equals(name))
property.setText(paging);
}

//持久化
<span style="white-space:pre">			XMLWriter </span>writer = new XMLWriter(new FileWriter("setting.xml"));
<span style="white-space:pre">			</span>writer.write(xmlDoc);

补充：

如果标签带有属性，如下xml

<span style="color:#333333;"><?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property>
<property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<property name="hibernate.connection.url">(DESCRIPTION=(LOAD_BALANCE=yes)(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=127.0.0.1)(PORT=1521))(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.1.3)(PORT=1521)))(CONNECT_DATA=(SERVER=dedicated)(SERVICE_NAME=wait)))</property>
<property name="hibernate.connection.username">system</property>
<property name="hibernate.connection.password">Ze25506065</property>
<property name="hibernate.cache.use_query_cache">false</property>
<property name="hibernate.cache.use_second_level_cache">false</property>
<property name="hibernate.show_sql">true</property>
</session-factory>
</hibernate-configuration></span>

jdk读：

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = dbf.newDocumentBuilder();
xmlDoc = builder.parse("src\\hibernate.cfg.xml");
NodeList nodeList = xmlDoc.getElementsByTagName("session-factory");
NodeList databaseList = nodeList.item(0).getChildNodes();
for(int i = 0, len = databaseList.getLength(); i < len; i++)
{
Node childNode = databaseList.item(i);
if (childNode instanceof Element)
{

String childName = ((Element)childNode).getAttribute("name");
if("hibernate.dialect".equals(childName))
childNode.getFirstChild().setNodeValue(dialect.get(useSql));
else if("hibernate.connection.driver_class".equals(childName))
childNode.getFirstChild().setNodeValue(driver);
else if("hibernate.connection.url".equals(childName))
childNode.getFirstChild().setNodeValue(url);
else if("hibernate.connection.username".equals(childName))
childNode.getFirstChild().setNodeValue(user);
else if("hibernate.connection.password".equals(childName))
childNode.getFirstChild().setNodeValue(password);
}
}

dom4j写：

SAXReader reader = new SAXReader()；
Document xmlDoc = reader.read(new File("src\\hibernate.cfg.xml"));
List<Element> properties = root.elements("session-factory");
for(Element property : properties)
{
List<Element> list = property.elements();
for(Iterator<Element> iter = list.iterator(); iter.hasNext();)
{
Element e = iter.next();
String name = e.attributeValue("name");
if("hibernate.dialect".equals(name))
e.setText(dialect.get(useSql));
else if("hibernate.connection.driver_class".equals(name))
e.setText(driver);
else if("hibernate.connection.url".equals(name))
e.setText(url);
else if("hibernate.connection.username".equals(name))
e.setText(user);
else if("hibernate.connection.password".equals(name))
e.setText(password);
}
}

读写都差不多，写就是设置标签的值在写入文件

注意：

用jdk写入xml会改变xml的头标签，至于解决方法我没探究，而dom4j就不会改写头标签