mvchelper.java

此程序都是企业级 的数据库开发程序 全面揭示了JAVA对数据库的操作

package mvc;

/* Standard Java Packages */
import java.util.Properties;
import java.io.File;
import java.io.FileWriter;
import java.io.FileInputStream;

/* Imported from the J2EE or JBoss servlet.jar */
import javax.servlet.jsp.JspWriter;

/* Imported from xerces.jar */
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.apache.xml.serialize.OutputFormat;
import org.apache.xml.serialize.XMLSerializer;

public class MVCHelper {

  /* Properties object containing all of the XSL File Names and the Request.Action key */
  private static Properties xslFileNames = new Properties();

  /* Location of the XSL Configuration Information File */
  private static String XSLCONFIGPROPERTIES = 
    new String("c:\\jakarta-tomcat-3.2.2\\webapps\\begjdb\\etc\\xslConfig.properties");

  /*
   * This method will retrieve the name of an XSL file from the xslFileNames object.  It
   * does this by appending the _request and _action parameters into a string that looks
   * like this:
   * Request.Action
   * This string created from the two method parameters is used as a key
   * to search xslFileNames for the appropriate file names.
   */
  public static String getXSLFileName(String _request, 
                                      String _action) throws Exception {

    /* If the xslFileNames object is empty, load the data from the configuration fiel */
    if (xslFileNames.isEmpty()) {
      xslFileNames.load(new FileInputStream(XSLCONFIGPROPERTIES));
    } 

    /* Building the lookup key */
    StringBuffer key = new StringBuffer(_request);
    key.append(".");
    key.append(_action);

    /* Retrieving the string */
    String xslFileName = xslFileNames.getProperty(key.toString());

    /* If no file name was retrieved throw an exception */
    if (xslFileName == null) {
      throw new Exception("MVCHelper.getXSLFileName:  Unable to locate XSL file based on the request" 
                          + " and action passed.  Key=" + key.toString());
    } 

    return xslFileName;
  } 

  /*
   * The printDOM method will take the XML document and the File object
   * passed into the method and dump its contents out to a file.  This is
   * only here for debugging purposes and should not be used in production code.
   */
  public static void printDOM(Document _xmlDoc, 
                              File _outputFile) throws Exception {
    OutputFormat outputFormat = new OutputFormat(_xmlDoc);
    FileWriter fileWriter = new FileWriter(_outputFile);

    XMLSerializer xmlSerializer = new XMLSerializer(fileWriter, 
            outputFormat);
    xmlSerializer.asDOMSerializer();

    xmlSerializer.serialize(_xmlDoc.getDocumentElement());
  } 


  /*
   * The buildDBElement will add a text node onto an element and return it back to the
   * method that calls it.  This is simply a helper method that makes it easier to add
   * elements to another element.
   */
  public static Element buildDBElement(Document _xmlDoc, 
                                       String _elementName, 
                                       String _elementValue) throws Exception {

    Element item = _xmlDoc.createElement(_elementName);

    if (_elementValue == null) {
      item.appendChild(_xmlDoc.createTextNode(""));
    } else {
      item.appendChild(_xmlDoc.createTextNode(_elementValue));
    } 
    return item;
  } 


  /*
   * Builds a generic help screen.
   */
  public static void buildErrorPage(Exception _e, JspWriter _out) {
    try {
      _out.write("<H1>We are currently unable to process your request. : " 
                 + _e.toString() + "</H1>");
      System.out.println(_e.toString());
    } catch (Exception e) {
      System.out.println(_e.toString());
    } 
  } 
}