#副標=Java整合XML應用系列（14）：
#大標=應用JSP整合XML/XSL之解疑篇(下)
作者=鄧崇林


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      <clt:setVariable id="xml" type="String">orderConfirm.xml</clt:setVariable>
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      <clt:setVariable id="emailVar" type="String"><req:parameter name="email"/></clt:setVariable>
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      <clt:setVariable id="xsl" type="String"><%=xslString%></clt:setVariable>
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      <clt:setVariable name="xml" type="String">myNewOrder.xml</clt:setVariable>
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    private Object convert(String s, Class c) {}
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    package clt.taglibs.var;

    import javax.servlet.jsp.JspException;
    import javax.servlet.jsp.PageContext;
    import javax.servlet.jsp.tagext.BodyTagSupport;

    public class SetVariableTag extends BodyTagSupport {
      private String  name = null, type = null, value = null, content = null;
      public void setName(String name) {
        this.name = name;
      }  
      public void setType(String type) {
        this.type = "java.lang." + type;
      }
      public void setValue(String value) {
        this.value = value;
      }
      public int doEndTag() throws JspException {
        Class klass = null;
	if ((getId() == null) && (name == null)) {
	    throw new JspException("Must specify either 'id' or 'name' attribute!");
	}
        try {
            klass = Class.forName(type);
        } catch(ClassNotFoundException e) {
            e.printStackTrace();
            return EVAL_PAGE;
        }
        content = bodyContent.getString().trim();
        bodyContent.clearBody();
        // 當使用空標記元素<tag/>時，此一content不等於null，也不等於空白字串
        if (content == null && value == null) {
           return EVAL_PAGE;   
        } else if (value != null) { 
           // do nothing  
        } else if (content != null) {   
           value = content;
        }  

	if (getId() != null && (name == null)) {
            if (pageContext.getAttribute(getId()) != null) {
                // 已經訂有同名的 Scripting 變數名稱，也暗示存有JavaBean   
	        throw new JspException("Already specified 'id' attribute!");

            } else {
	        pageContext.setAttribute(getId(), convert(value, klass));
            }
        } else if (name != null) {
            if (pageContext.getAttribute(name) == null) {
	        throw new JspException("Cannot specify 'name' attribute!");
            } else {
                // 透過下列方法來建立該變數值
	        pageContext.setAttribute(name, convert(value, klass));
            }
	} else {
	    throw new JspException("Cannot work at all!");
	}
        return EVAL_PAGE;
      }
      //
      private Object convert(String s, Class c) throws JspException {
        try {
            if (s == null) {
                if (c.equals(Boolean.class) || c.equals(Boolean.TYPE))
                    s = "false";
                else
                    return null;
            }
    
            if (c.equals(Boolean.class) || c.equals(Boolean.TYPE) ) {
                if (s.equalsIgnoreCase("on") || s.equalsIgnoreCase("true"))
                    s = "true";
                else
                    s = "false";
                return new Boolean(s);
            } else if (c.equals(Byte.class) || c.equals(Byte.TYPE) ) {
                return new Byte(s);
            } else if (c.equals(Character.class) || c.equals(Character.TYPE)) {
                return s.length() > 0 ? new Character(s.charAt(0)) : null;
            } else if (c.equals(Short.class) || c.equals(Short.TYPE) ) {
                return new Short(s);
            } else if (c.equals(Integer.class) || c.equals(Integer.TYPE) ) {
                return new Integer(s);
            } else if (c.equals(Float.class) || c.equals(Float.TYPE) ) {
                return new Float(s);
            } else if (c.equals(Long.class) || c.equals(Long.TYPE) ) {
                return new Long(s);
            } else if (c.equals(Double.class) || c.equals(Double.TYPE) ) {
                return new Double(s);
            } else if (c.equals(String.class) ) {
                return s;
            } else {
                throw new JspException("unKnown type! ");
            }
        } catch (Exception ex) {
            throw new JspException(ex.getMessage());
        }
      }
      // 
      public void release() {
        type = value = content = null;
        super.release();
      }
    }
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    package clt.taglibs.var;

    import javax.servlet.jsp.tagext.TagData;
    import javax.servlet.jsp.tagext.TagExtraInfo;
    import javax.servlet.jsp.tagext.VariableInfo;

    public final class SetVariableTEI extends TagExtraInfo {
      public SetVariableTEI() {
        super();
      }
      public VariableInfo[] getVariableInfo(TagData data) {
        String varName = data.getId();
        if (varName == null) 
            varName = data.getAttributeString("name");
	return new VariableInfo[] {
	  new VariableInfo(varName,                         // "id"或"name"屬性所指定的描述變數名稱
	                   data.getAttributeString("type"), // 為變數設定恰當的資料型態
	                   (data.getId() != null ? true : false),
	                   VariableInfo.AT_END)
	};
      }
    }
==============<end>=====================
 
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    javac -d C:\tomcat32\webapps\runpc\WEB-INF\classes *.java
    cd ..\classes
    jar cvf varTags.jar  clt\taglibs\var\*.class
    move varTags.jar ..\lib
    del clt\taglibs\var\*.class
    cd ..\lib
    pause
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    <?xml version="1.0" encoding="Big5" ?>
    <!DOCTYPE taglib
            PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN"
            "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
    <!-- The tag library descriptor -->
    <taglib>
      <tlibversion>1.0</tlibversion>
      <jspversion>1.1</jspversion>
      <shortname></shortname>
      <tag>
        <name>setVariable</name>
        <tagclass>clt.taglibs.var.SetVariableTag</tagclass>
        <teiclass>clt.taglibs.var.SetVariableTEI</teiclass>
        <bodycontent>JSP</bodycontent>
        <info>Set scripting variable, author:鄧崇林</info>
        <attribute>
          <name>id</name>
          <required>no</required>
          <rtexprvalue>no</rtexprvalue>
        </attribute>
        <attribute>
          <name>name</name>
          <required>no</required>
          <rtexprvalue>yes</rtexprvalue>
        </attribute>
        <attribute>
          <name>type</name>
          <required>yes</required>
          <rtexprvalue>no</rtexprvalue>
        </attribute>
        <attribute>
          <name>value</name>
          <required>no</required>
          <rtexprvalue>yes</rtexprvalue>
        </attribute>
      </tag>
    </taglib>
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        <taglib>
          <taglib-uri>/clt.taglibs.var</taglib-uri>
          <taglib-location>varTags.tld</taglib-location>
        </taglib>
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    <%@ taglib uri="/clt.taglibs.var" prefix="clt" %>
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