JSP标签

JSP标签

2. UI标签
1.z:set
自定义一个set标签，out标签
1.set

private static final long serialVersionUID = 4965191755704898746L;
	
	private String var;
	private Object value;
	
	@Override
	public int doStartTag() throws JspException {
		pageContext.setAttribute(var, value);
//		HttpServletRequest request=(HttpServletRequest) pageContext.getRequest();//开发权限标签需要用到
		return SKIP_BODY;
	}
	

	

private static final long serialVersionUID = 1L;

private Object value;

public Object getValue() {
	return value;
}

public void setValue(Object value) {
	this.value = value;
}

@Override
public int doStartTag() throws JspException {
	JspWriter out=pageContext.getOut();
	try {
		out.print(value.toString());
	} catch (IOException e) {
		e.printStackTrace();
	}
	return SKIP_BODY;
}

	
	public String getVar() {
		return var;
	}
	public void setVar(String var) {
		this.var = var;
	}
	public Object getValue() {
		return value;
	}
	public void setValue(Object value) {
		this.value = value;
	}

在tld文件中设置

  <tag>
    <name>set</name>
    <tag-class>com.zking.jsp.day02.OutTag</tag-class>
    <body-content>JSP</body-content>
     <attribute>
        <name>var</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>

  <tag>
    <name>out</name>
    <tag-class>com.zking.jsp.day02.OutTag</tag-class>
    <body-content>JSP</body-content>
     <attribute>
        <name>value</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
  

最后在jsp文件中实现

<z:set var="name" value="zhangsan"></z:set>
<z:out value="${name }"></z:out>

m:select 标签
1.比如说我们需要学生姓名，编号得下拉框
我们需要一个学生得实体类

public class Student {
	private String sid ;
	private String sname;
	public String getSid() {
		return sid;
	}
	public void setSid(String sid) {
		this.sid = sid;
	}
	public String getSname() {
		return sname;
	}
	public void setSname(String sname) {
		this.sname = sname;
	}
	public Student(String sid, String sname) {
		super();
		this.sid = sid;
		this.sname = sname;
	}
	public Student() {
		super();
	}
	
	

然后我们新建一个select得类

/**
 * 1.值得传递 id，name
 * 2.数据源 items
 * 3.展示列与数据存储与实体类dui应关系  textKey textVal
 * 4.数据回显 selectedVal
 * 5.可能下拉框默认值  headerTextKey headerTextVal
 */

public class SelectTag extends BodyTagSupport{

	/**
	 * 
	 */
	private static final long serialVersionUID = 5375902073989817712L;
	private String id;
	private String name;
	private List<Object> items = new ArrayList<Object>();
	private String textKey;//id
	private String textVal;
	private String selectedVal;
	private String headerTextKey;
	private String headerTextVal;
	
	
	@Override
	public int doStartTag() throws JspException {
		JspWriter out = pageContext.getOut();
		try {
			try {
				out.print(toHTML());
			} catch (NoSuchFieldException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (SecurityException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IllegalArgumentException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IllegalAccessException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (InvocationTargetException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (NoSuchMethodException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return super.doStartTag();
	}
	
	
	
	
	
	private String toHTML() throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException, InvocationTargetException, NoSuchMethodException {
		StringBuffer sb = new StringBuffer();
		sb.append("<select id='"+id+"' name='"+name+"'>");
		
		String value;
		String html;
		if(!(headerTextKey==null || "".equals(headerTextKey)||
				headerTextVal==null || "".equals(headerTextVal))) {
			sb.append("<option select value='"+headerTextKey+"'>"+headerTextVal+"</option>");
		}
		
		for (Object obj : items) {
			Field	textKeyField = obj.getClass().getDeclaredField(textKey);
			textKeyField.setAccessible(true);
			value = (String) textKeyField.get(obj);
			html =(String) PropertyUtils.getProperty(obj, textVal);
			if(value.equals(selectedVal)) {
				sb.append("<option selected value='"+value+"'>"+html+"</option>");
				
			}else {
				sb.append("<option value='"+value+"'>"+html+"</option>");
			}
		
		}
		
		
		sb.append("</select>");
		return sb.toString();
	}





	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public List<Object> getItems() {
		return items;
	}
	public void setItems(List<Object> items) {
		this.items = items;
	}
	public String getTextKey() {
		return textKey;
	}
	public void setTextKey(String textKey) {
		this.textKey = textKey;
	}
	public String getTextVal() {
		return textVal;
	}
	public void setTextVal(String textVal) {
		this.textVal = textVal;
	}
	public String getSelectedVal() {
		return selectedVal;
	}
	public void setSelectedVal(String selectedVal) {
		this.selectedVal = selectedVal;
	}
	public String getHeaderTextKey() {
		return headerTextKey;
	}
	public void setHeaderTextKey(String headerTextKey) {
		this.headerTextKey = headerTextKey;
	}
	public String getHeaderTextVal() {
		return headerTextVal;
	}
	public void setHeaderTextVal(String headerTextVal) {
		this.headerTextVal = headerTextVal;
	}
	public static long getSerialversionuid() {
		return serialVersionUID;
	}
	public SelectTag(String id, String name, List<Object> items, String textKey, String textVal, String selectedVal,
			String headerTextKey, String headerTextVal) {
		super();
		this.id = id;
		this.name = name;
		this.items = items;
		this.textKey = textKey;
		this.textVal = textVal;
		this.selectedVal = selectedVal;
		this.headerTextKey = headerTextKey;
		this.headerTextVal = headerTextVal;
	}
	public SelectTag() {
		super();
	}

然后我们需要在xml文件中实现select标签

 <tag>
    <name>select</name>
    <tag-class>com.zking.jsp.day02.SelectTag</tag-class>
    <body-content>JSP</body-content>
     <attribute>
        <name>id</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    
     <attribute>
        <name>items</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
    
     <attribute>
        <name>textKey</name>
        <required>true</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    
     <attribute>
        <name>textVal</name>
        <required>true</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    
     <attribute>
        <name>selectedVal</name>
        <required>false</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
    
     <attribute>
        <name>headerTextKey</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    
     <attribute>
        <name>headerTextVal</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
  </tag>

接着就可以在jsp文件中进行实现

<% 
	List ls = new ArrayList();
ls.add(new Student("001","xiaowang"));
ls.add(new Student("002","xiaoli"));
ls.add(new Student("003","xiaosan"));
request.setAttribute("stus", ls);


%>

<z:foreach items="${stus }" var="stu">
	${stu.id },${stu.sname }<br>

</z:foreach>

<z:select selectedVal="002" headerTextKey="-1" headerTextVal="===请选择===" textVal="name" items="${stus }" textKey="id"></z:select>

注1：JspWriter writer = pageContext.getOut();

3. 控制标签
实现标签得步骤基本上都是一样的
下面对if标签和foeach标签进行一个案例
我们首先需要一个学生的实体类
如上一个select标签
1. m:if

 */
	private static final long serialVersionUID = -8477321984637500253L;
	
	private boolean test;
	
	public boolean isTest(){
		return test;
		
	}
	
	public void setTest(boolean test) {
		this.test = test;
	}
	
	@Override
	public int doStartTag() throws JspException {
		// TODO Auto-generated method stub
		return test ? EVAL_BODY_INCLUDE : SKIP_BODY;
	}
}

接着

 <tag>
    <name>if</name>
    <tag-class>com.zking.jsp.day02.IfTag</tag-class>
    <body-content>JSP</body-content>
     <attribute>
        <name>test</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>

测试

<z:if test="true">zhangsan</z:if>
<z:if test="false">zhan</z:if>

2.m:forEach 3

/**
	 * 
	 */
	private static final long serialVersionUID = -1614598923980260048L;
	
	private String var;
	private List<Object> items = new ArrayList<>();
	
	@Override
	public int doStartTag() throws JspException {
		if(items.size()==0) {
			return SKIP_BODY;
		}else {
			Iterator<Object> it = items.iterator();
			pageContext.setAttribute(var, it.next());
			pageContext.setAttribute("it", it);
			return EVAL_BODY_INCLUDE;
		}
	}
	
	
	@Override
	public int doAfterBody() throws JspException {
		Iterator<Object> it=(Iterator<Object>) pageContext.getAttribute("it");
		if(it.hasNext()) {
			return EVAL_BODY_AGAIN;
		}
		return EVAL_PAGE;
	}

接着

  <tag>
    <name>foreach</name>
    <tag-class>com.zking.jsp.day02.Foreach</tag-class>
    <body-content>JSP</body-content>
     <attribute>
        <name>items</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
  

测试

<% 
	List ls = new ArrayList();
ls.add(new Student("001","xiaowang"));
ls.add(new Student("002","xiaoli"));
ls.add(new Student("003","xiaosan"));
request.setAttribute("stus", ls);


%>

<z:foreach items="${stus }" var="stu">
	${stu.id },${stu.sname }<br>

注1：page(pageContext)|request(…)|session(…)|application(…)
存储和交换数据