JSP标签_2

其他 2019-06-28 04:14:17 阅读次数: 0

文章目录

自定义标签开发步骤

1.1 助手类
1.2 tld
1.3 taglib

out 标签

第一步先写一个助手类代码如下：
继承了BodyTagSupport

public class OutTag extends BodyTagSupport {

	private static final long serialVersionUID = -2288689618162607401L;
	
	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();//拿到输出流
		try {
			out.print(value.toString());
		} catch (IOException e) {
			e.printStackTrace();
		}
		return SKIP_BODY;
	}
	
}

第二步写tld

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

第三步输出值

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

set 标签

步骤和out一样，代码相似，就展示重要步骤了
代码如下

public class SetTag extends BodyTagSupport {
	private static final long serialVersionUID = -547043983190642867L;
	
	private String var;
	private Object value;
	
	@Override
	public int doStartTag() throws JspException {
		pageContext.setAttribute(var, value);
		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;
	}
	
	
	
}

if 标签

if标签就比较简单了
代码如下：

public class IfTag extends BodyTagSupport {
	private static final long serialVersionUID = -2838015447802594985L;
	
	private boolean test;

	public boolean isTest() {
		return test;
	}

	public void setTest(boolean test) {
		this.test = test;
	}
	
	@Override
	public int doStartTag() throws JspException {
		return test ? EVAL_BODY_INCLUDE : SKIP_BODY;
	}

tld配置的话有多少个属性就写多少个

forEach标签

public class ForeachTag extends BodyTagSupport {
	private static final long serialVersionUID = -5619053683239283643L;
	
	private String var;
	private List<Object> items = new ArrayList<>();
	
	/**
	 * 执行完这个方法的时候，var所代表的指针一定要向下移动一位
	 */
	@Override
	public int doStartTag() throws JspException {
		if(items.size() == 0) {
			return SKIP_BODY;
		}
		else {
			Iterator<Object> it = items.iterator();//获取迭代器
			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()) {
			pageContext.setAttribute(var, it.next());
			pageContext.setAttribute("it", it);
			return EVAL_BODY_AGAIN;
		}
		return EVAL_PAGE;
	}
	
	public String getVar() {
		return var;
	}
	public void setVar(String var) {
		this.var = var;
	}
	public List<Object> getItems() {
		return items;
	}
	public void setItems(List<Object> items) {
		this.items = items;
	}
	
	

}

select标签

select标签是我们的大bos

首先他的继承助手类是

public class SelectTag extends BodyTagSupport {

}

public class SelectTag extends BodyTagSupport {
private static final long serialVersionUID = -3939376511758370301L;
private String id;
private String name;
private List items = new ArrayList<>();
private String textkey;
private String textVal;
private String selectedVal;
private String headerTextKey;
private String headerTextVal;

@Override
public int doStartTag() throws JspException {
	JspWriter out = pageContext.getOut();
	try {
		out.print(toHTML());
	} catch (IOException e) {
		e.printStackTrace();
	} catch (NoSuchFieldException e) {
		e.printStackTrace();
	} catch (SecurityException e) {
		e.printStackTrace();
	} catch (IllegalArgumentException e) {
		e.printStackTrace();
	} catch (IllegalAccessException e) {
		e.printStackTrace();
	} catch (InvocationTargetException e) {
		e.printStackTrace();
	} catch (NoSuchMethodException e) {
		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+"'>");
	
	if(!(headerTextKey==null||"".equals(headerTextKey)||headerTextVal==null||"".equals(headerTextVal))) {
		sb.append("<option value='"+headerTextKey+"'>"+headerTextVal+"</option>");
	}

	String value;
	String html;
	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 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 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 String getName() {
	return name;
}


public void setName(String name) {
	this.name = name;
}


public String getSelectedVal() {
	return selectedVal;
}


public void setSelectedVal(String selectedVal) {
	this.selectedVal = selectedVal;
}
}

注意：一定记得写set，get

tld配置代码：

 <tag>
    <name>select</name>
    <tag-class>com.zrh.jsp.day02.SelectTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>id</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
        <name>name</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>
  


	<%
		List list = new ArrayList();
		list.add(new Student("001","xiaoli"));
		list.add(new Student("002","xiaogfhd"));
		list.add(new Student("003","xiaoshs"));
	   request.setAttribute("stus", list);
	   
	  
	    
	%>
<z:foreach items="${stus }" var="stu">
	${stu.id },${stu.name }<br>
</z:foreach>

<z:select headerTextKey="-1" headerTextVal="====请选择====" textVal="name" items="${stus }" selectedVal="2" textKey="id"></z:select>

输出结果为：
在这里插入图片描述

checkbox标签

checkTag类

/**
 * 1、值得传递  id name
 * 2、数据源  items 
 * 3、展示列与数据存储列(value)与实体类的对应关系   
 * 		textVal	textkey
 * 4、数据回显 selectedVal
 * 5、可能下拉框有默认值（头标签） headerTextKey  headerTextVal
 * @author zrh
 *
 */

public class CheckTag extends BodyTagSupport {
	private static final long serialVersionUID = -3939376511758370301L;
	
	private String textkey;
	private String textVal;
	private List<Object> checkVal = new ArrayList<>();
	private List<Object> items = new ArrayList<>();
	
	
	@Override
	public int doStartTag() throws JspException {
		JspWriter out = pageContext.getOut();
		try {
			out.print(toHTML());
		} catch (IOException e) {
			e.printStackTrace();
		} catch (NoSuchFieldException e) {
			e.printStackTrace();
		} catch (SecurityException e) {
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			e.printStackTrace();
		}
		return super.doStartTag();
	}
	
	private String toHTML() throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException, InvocationTargetException, NoSuchMethodException {
		StringBuffer sb = new StringBuffer();
		

		String value;
		String html;
		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(checkVal.contains(value)) {
				sb.append("<input checked type='checkbox' value='"+value+"' />"+html+"");
			}
			else {
				sb.append("<input type='checkbox' value='"+value+"'>"+html+"");
			}
		}
		sb.append("</select>");
		return sb.toString();
	}


	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 List<Object> getCheckVal() {
		return checkVal;
	}

	public void setCheckVal(List<Object> checkVal) {
		this.checkVal = checkVal;
	}

	public List<Object> getItems() {
		return items;
	}

	public void setItems(List<Object> items) {
		this.items = items;
	}

}

tld配置

<tag>
    <name>checkbox</name>
    <tag-class> com.zrh.jsp.day02.CheckTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>textkey</name>
        <required>true</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
        <name>textVal</name>
        <required>true</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
        <name>checkVal</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
    <attribute>
        <name>items</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>


	<%
		List list = new ArrayList();
		list.add(new Student("001","xiaoli"));
		list.add(new Student("002","xiaogfhd"));
		list.add(new Student("003","xiaoshs"));
	   request.setAttribute("stus", list);
	   
	   
	   List l = new ArrayList();
	   l.add("001");
	   l.add("002");
	   request.setAttribute("list", l);
	    
	%>
<z:foreach items="${stus }" var="stu">
	${stu.id },${stu.name }<br>
</z:foreach>


<z:checkbox textkey="id" textVal="name" items="${stus }" checkVal="${list }"></z:checkbox>
</body>

结果如下
在这里插入图片描述

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