在项目中经常会遇到文件加载并解析的问题
加载Properties文件很简单 可以直接使用Properties提供的方法就可以了
如果是加载xml文件
可以使用 MyTest.class.getClass().getClassLoader().getResourceAsStream(fileName);
try 
{
DocumentBuilder db;
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setValidating(true);
dbf.setNamespaceAware(false);
db = dbf.newDocumentBuilder();
db.setEntityResolver(new EntityResolver() {
public InputSource resolveEntity(String publicId, String systemId) {
if (systemId.endsWith("mapping.dtd")) {
InputStream in = MappingObjectInit.class.getResourceAsStream("mapping.dtd");
if (in == null) {
LogLog.error("Could not find [mapping.dtd]. Used [" + MappingObjectInit.class.getClassLoader() + "] class loader in the search.");
return null;
} else {
return new InputSource(in);
}
} else {
return null;
}
}
});
db.setErrorHandler(new ErrorHandler() {
public void warning(SAXParseException exception) {
}
public void error(SAXParseException exception) throws SAXException {
logger.error(exception.getMessage() + " at (" + exception.getLineNumber() + ":" + exception.getColumnNumber() + ")");
throw exception;
}
public void fatalError(SAXParseException exception) throws SAXException {
logger.error(exception.getMessage() + " at (" + exception.getLineNumber() + ":" + exception.getColumnNumber() + ")");
throw exception;
}
});
return db;
} catch (Exception e) {
logger.error("", e);
}上面得到DocumentBuilder对象，然后就可以解析xml了
private static void loadConfigurationFile(String fileName, DocumentBuilder db) {
Document doc = null;
InputStream is = null;
try {
is = MappingObjectInit.class.getClass().getClassLoader().getResourceAsStream(fileName);
doc = db.parse(is);
} catch (Exception e) {
final String s = "Caught exception while loading file " + fileName;
logger.error(s, e);
throw new DataAccessException(s, e);
} finally {
if (is != null) {
try {
is.close();
} catch (IOException e) {
logger.error("Unable to close input stream", e);
}
}
}
Element rootElement = doc.getDocumentElement();
NodeList children = rootElement.getChildNodes();
int childSize = children.getLength();
for (int i = 0; i < childSize; i++) {
Node childNode = children.item(i);
if (childNode instanceof Element) {
Element child = (Element) childNode;
final String nodeName = child.getNodeName();
if (nodeName.equals("mapping")) {
String className = child.getAttribute("class");
Class cls;
try {
cls = Class.forName(className);
MappingMgt.reg(cls);
} catch (ClassNotFoundException e) {
logger.error("load configurFile from :"+fileName, e);
}
}
}
}
if (logger.isInfoEnabled()) {
logger.info("Loaded Engine configuration from: " + fileName);
}
} 如果使用了spring 还可以使用spring的文件加载类来加载
<bean id="propertyConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>file:${config.path}jdbc.properties</value>
<value>file:${config.path}jms.properties</value>
</list>
</property>
</bean>
String inputstream 互相转换
1. String --> InputStream
InputStream String2InputStream(String str){
ByteArrayInputStream stream = new ByteArrayInputStream(str.getBytes());
return stream;
}
2. InputStream --> String
String inputStream2String(InputStream is){
BufferedReader in = new BufferedReader(new InputStreamReader(is));
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = in.readLine()) != null){
buffer.append(line);
}
return buffer.toString();
}
3、File --> InputStream
InputStream in = new InputStream(new FileInputStream(File));
上面这行报错，new InputStream 报错
下面这样写即可
new FileInputStream(file)
4、InputStream --> File
public void inputstreamtofile(InputStream ins,File file){
OutputStream os = new FileOutputStream(file);
int bytesRead = 0;
byte[] buffer = new byte[8192];
while ((bytesRead = ins.read(buffer, 0, 8192)) != -1) {
os.write(buffer, 0, bytesRead);
}
os.close();
ins.close();
}