iBatis开发详解（8）---使用XML

   在实际应用中，很多时候我们使用到了XML格式的数据，比如FushionChart，iBatis允许使用XML作为数据库查询操作的参数，也允许数据库查询结果返回一个XML格式的数据。如果不是必须，使用XML并不会给带来什么价值，甚至不如直接使用POJO，因为它是强类型的。下面先来看看使用XML作为参数的情况，做参数时，可以使用String，也可以使用DOM来传递，此时的XML结构并不严格要求，只要格式良好即可。结合实例，比如有如下的XML片段： 

<parameter><userId>1</userId></parameter>  

<select id="getUserByXMLId" parameterClass="xml" resultClass="User">  
    select * from users where userId=#userId#  
</select>  

   把parameterClass属性写成xml就行了，resultClass可以是你定义的Bean类型或Map，下面来看程序：

String parameter = "<parameter><userId>1</userId></parameter>";  
User user = (User) sqlMap.queryForObject("User.getUserByXMLId",  
        parameter);  
System.out.println(user);  

public static void main(String[] args) throws SQLException,  
            ParserConfigurationException {  
    //创建XML文档  
    org.w3c.dom.Document parameterDocument = DocumentBuilderFactory  
            .newInstance().newDocumentBuilder().newDocument();  
    //创建根元素  
    org.w3c.dom.Element paramElement = parameterDocument  
            .createElement("parameterDocument");  
    //创建userId元素  
    org.w3c.dom.Element userIdElement = parameterDocument  
.createElement("userId");  
    //设置userId元素的值  
    userIdElement.setTextContent("1");  
    //元素关系添加  
    paramElement.appendChild(userIdElement);  
    parameterDocument.appendChild(paramElement);  
    //数据查询  
    User user = (User) sqlMap.queryForObject("User.getUserByXMLId",  
            parameterDocument);  
    System.out.println(user);  
}  

package ibatis.util;  
import java.io.IOException;  
import org.dom4j.Document;  
import org.dom4j.DocumentHelper;  
import org.dom4j.Element;  
/** 
 * 使用dom4j生成XML工具类 
 *  
 * @author Sarin 
 *  
 */  
public class XMLUtil {  
    private Document document = null;  
    public Document getDocument() {  
        return document;  
    }  
    /** 
     * 构造方法，初始化Document 
     */  
    public XMLUtil() {  
        document = DocumentHelper.createDocument();  
    }  
    /** 
     * 生成根节点 
     *  
     * @param rootName 
     * @return 
     */  
    public Element addRoot(String rootName) {  
        Element root = document.addElement(rootName);  
        return root;  
    }  
    /** 
     * 生成节点 
     *  
     * @param parentElement 
     * @param elementName 
     * @return 
     */  
    public Element addNode(Element parentElement, String elementName) {  
        Element node = parentElement.addElement(elementName);  
        return node;  
    }  
    /** 
     * 为节点增加一个属性 
     *  
     * @param thisElement 
     * @param attributeName 
     * @param attributeValue 
     */  
    public void addAttribute(Element thisElement, String attributeName,  
            String attributeValue) {  
        thisElement.addAttribute(attributeName, attributeValue);  
    }  
    /** 
     * 为节点增加多个属性 
     *  
     * @param thisElement 
     * @param attributeNames 
     * @param attributeValues 
     */  
    public void addAttributes(Element thisElement, String[] attributeNames,  
            String[] attributeValues) {  
        for (int i = 0; i < attributeNames.length; i++) {  
            thisElement.addAttribute(attributeNames[i], attributeValues[i]);  
        }  
    }  
    /** 
     * 增加节点的值 
     *  
     * @param thisElement 
     * @param text 
     */  
    public void addText(Element thisElement, String text) {  
        thisElement.addText(text);  
    }  
    /** 
     * 获取最终的XML 
     *  
     * @return 
     * @throws IOException 
     */  
    public String getXML() {  
        return document.asXML().substring(39);  
    }  
}  

XMLUtil xmlParameter = new XMLUtil();  
Element parameter = xmlParameter.addRoot("parameter");  
Element userId = xmlParameter.addNode(parameter, "userId");  
userId.addText("1");  
System.out.println(xmlParameter.getXML());  
User user = (User) sqlMap.queryForObject("User.getUserByXMLId",  
        xmlParameter.getXML());  
System.out.println(user);  

<select id="getXMLValueByUserId" resultClass="xml" xmlResultName="User" parameterClass="int">  
        select * from users where userId=#userId#  
</select>  

String xmlUser = (String) sqlMap.queryForObject(  
        "User.getXMLValueByUserId", new Integer(1));  
System.out.println(xmlUser);  

<?xml version="1.0" encoding="UTF-8" standalone="no"?>  
<User>  
<userId>1</userId>  
<userName>Sarin</userName>  
<password>123</password>  
<age>23</age>  
<mobile>15940912345</mobile>  
<email>gmail@gmail.com</email>  
</User>  

<select id="getUserXMLValue" resultClass="xml" xmlResultName="User">  
    select * from users  
</select>  

List xmlUserList = sqlMap.queryForList("User.getUserXMLValue");  
System.out.println(xmlUserList);  

public String toXML() {  
    StringBuffer xmlValue = new StringBuffer();  
    xmlValue.append("<user>");  
    xmlValue.append("<userId>").append(getUserId()).append("</userId>");  
    xmlValue.append("<userName>").append(getUserName()).append("</userName>");  
    xmlValue.append("<password>").append(getPassword()).append("</password>");  
    xmlValue.append("<mobile>").append(getMobile()).append("</mobile>");  
    xmlValue.append("<email>").append(getEmail()).append("</email>");  
    xmlValue.append("<age>").append(getAge()).append("</age>");  
    xmlValue.append("</user>");  
    return xmlValue.toString();  
}  

List<User> userList = sqlMap.queryForList("User.getAllUsers");  
StringBuffer xmlUserList = new StringBuffer("<users>");  
for (User user : userList) {  
    xmlUserList.append(user.toXML());  
}  
xmlUserList.append("</users>");  
System.out.println(xmlUserList.toString());  

package ibatis.util;  
import java.beans.BeanInfo;  
import java.beans.Introspector;  
import java.beans.PropertyDescriptor;  
import java.lang.reflect.Method;  
public class BeanToXML {  
    private Class beanClass;  
    private BeanInfo beanInfo;  
    private String name;  
    public BeanToXML(Class beanClass, String name) throws Exception {  
        this.beanClass = beanClass;  
        this.name = name;  
        beanInfo = Introspector.getBeanInfo(beanClass);  
    }  
    public String convertToXML(Object obj) throws Exception {  
        StringBuffer xmlValue = new StringBuffer();  
        if (obj.getClass().isAssignableFrom(beanClass)) {  
            PropertyDescriptor[] pd = beanInfo.getPropertyDescriptors();  
            if (pd.length > 0) {  
                xmlValue.append("<").append(name).append(">");  
                for (int i = 0; i < pd.length; i++) {  
                    xmlValue.append(getProperty(obj, pd[i]));  
                }  
                xmlValue.append("</").append(name).append(">");  
            } else {  
                xmlValue.append("<").append(name).append("/>");  
            }  
        } else {  
            throw new ClassCastException("Class " + obj.getClass().getName()  
                    + " is not compatible with " + beanClass.getName());  
        }  
        return xmlValue.toString();  
    }  
    private String getProperty(Object obj, PropertyDescriptor pd)  
            throws Exception {  
        StringBuffer propertyValue = new StringBuffer();  
        Method method = pd.getReadMethod();  
        Object bodyValue = method.invoke(obj);  
        if (null == bodyValue) {            propertyValue.append("<").append(pd.getName()).append("/>");  
        } else {            propertyValue.append("<").append(pd.getName()).append(">");  
            propertyValue.append(bodyValue.toString());         propertyValue.append("</").append(pd.getName()).append(">");  
        }  
        return propertyValue.toString();  
    }  
}  

BeanToXML btx = new BeanToXML(User.class, "user");  
List<User> userList = sqlMap.queryForList("User.getAllUsers");  
StringBuffer xmlUserList = new StringBuffer("<users>");  
for (User user : userList) {  
    xmlUserList.append(btx.convertToXML(user));  
}  
xmlUserList.append("</users>");  
System.out.println(xmlUserList.toString());