jxpath學習筆記

get set 參考 BeanUtil 包 和 Xpath

http://commons.apache.org/　的 jxpath User's Guide

類的加載

JXPathContext context=JXPathContext.newContext( obj );
//和 xpath 的 范圍確定

一般取值 存值　

String fName=(String)context.getValue("firstName"); //setValue
//參考 http://www.blogjava.net/Good-Game/archive/2007/08/10/135739.html

一般的統計和使用　c　為 list [id,name,.....]

JXPathContext context = JXPathContext.newContext(c);
System.out.println( context.getValue("count( .[name='oo' and id='1' ] )") ); //對象 name=oo 和 id=1的有多少個
System.out.println( context.getValue("sum( .[name='oo' and id='1' ]/id )") );//對象name=oo和id=1的所有id相加

得到集合

Iterator threeBooks=context.iterate("books[position()<4]");
//xpath 的位置函數 position 其他函數參考 http://www.w3.org/TR/xpath　
//4 Core Function Library

xpath 使用

public class Employee {
    private Map addressMap = new HashMap();
    {        addressMap.put("home", new Address(...));
        addressMap.put("office", new Address(...));
    }
    public Map getAddresses(){
      return addressMap;
    }
    ...
}
 String homeZipCode = (String)context. getValue("addresses[@name='home']/zipCode");
//使用的是 addressMap map 的 key = home 的Address類屬性的 zipCode

xml 在程序 與 xpath 的切入點

<?xml version="1.0" ?>
    <vendor>
      <location id="store101">
        <address>
          <street>Orchard Road</street>
        </address>
      </location>
      <location id="store102">
        <address>
          <street>Tangerine Drive</street>
        </address>
      </location>
    </vendor>
class Company {
    private Container locations = null;
    public Container getLocations(){
        if (locations == null){
            URL url = getClass().getResource("Vendor.xml");
            locations = new XMLDocumentContainer(url);
        }
        return locations;
    }
 }
  ...
  context = JXPathContext.newContext(new Company());
  ...
  String street = (String)context.getValue(
                "locations/vendor/location[@id = 'store102']//street");
// 類Container的 屬性 locations 頭 vendor(xml內) .....

建立 Path工廠 就是 自定義字符串 得到 自定義類

public class AddressFactory extends AbstractFactory {
    public boolean createObject(JXPathContext context, Pointer pointer,
                                Object parent, String name, int index){
     if ((parent instanceof Employee) && name.equals("address"){
       ((Employee)parent).setAddress(new Address());
       return true;
     }
     return false;
   }
 }
 JXPathContext context = JXPathContext.newContext(emp);
 context.setFactory(new AddressFactory());
 context.createPath("address");
 context.createPathAndSetValue("address/zipCode", "90190");
// emp 類就是 createObject方法中的 Object
//運行解析到 address字符 就進入 if中

建立內參

JXPathContext context = JXPathContext.newContext(auth);
 context.getVariables().declareVariable("index", new Integer(2));
 context.setValue("$index", new Integer(3));
 Book secondBook = (Book)context.getValue("books[$index]");
// $index 為 3

確定范圍

JXPathContext context = JXPathContext.newContext(bean);
 Pointer addressPtr = context.getPointer("/employees[1]/addresses[2]");
 JXPathContext relativeContext =
               context.getRelativeContext(addressPtr);
 String zipCode = (String)relativeContext.getValue("zipCode");
//可以用 xpath 確定范圍 很好 呵呵

方法的聯系應用

public class Formats {
    public static String date(Date d, String pattern){
        return new SimpleDateFormat(pattern).format(d);
    }
    ...
}
context.setFunctions(new ClassFunctions(Formats.class, "format"));
//方法的設置 format
...
context.getVariables().declareVariable("today", new Date());
 String today =
     (String)context.getValue("format:date($today, 'MM/dd/yyyy')");

心得： 代碼可以寫成什麼樣呢~~ (JXpath)