在工程中定义jsp页面可以使用的标签

1.咱们先引入java.servlet.jsp包。因为是maven项目，直接引入依赖

<dependency>
			<groupId>javax.servlet.jsp</groupId>
			<artifactId>jsp-api</artifactId>
			<version>2.2.1-b03</version>
			<scope>provided</scope>
		</dependency>

2.定义limit-taglib.tld文件，该文件中定义了limit标签和副标签，使用的时候为limit:checker相似 其中的target-class即为对应的操做实体类，attribute为实体类中的属性。

<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN" "http://java.sun.com/j2ee/dtd/web-jsptaglibrary_1_2.dtd">
<taglib>
  <tlib-version>1.0</tlib-version>
  <jsp-version>1.2</jsp-version>
  <short-name>limit</short-name>
  <tag>
  	<name>checker</name>
  	<tag-class>com.credithc.workorder.manage.utils.dict.ViewPowerChecker</tag-class>
  	<attribute>
  		<name>standard</name>
  		<required>true</required>
		<rtexprvalue>true</rtexprvalue>
  	</attribute>
  	<attribute>
  		<name>standardList</name>
  		<required>true</required>
		<rtexprvalue>true</rtexprvalue>
  	</attribute>
  </tag>
  <tag>
  	<name>success</name>
  	<tag-class>com.credithc.workorder.manage.utils.dict.ViewPowerSuccessTag</tag-class>
  </tag>
  <tag>
  	<name>fail</name>
  	<tag-class>com.credithc.workorder.manage.utils.dict.ViewPowerFailTag</tag-class>
  </tag>
</taglib>

3.定义对应的实体类

public class ViewPowerChecker extends TagSupport{
	//这里必须继承tagSupport类，重写他的doStartTag()方法，标签在校验的时候走的就是这个方法
	/**
	 * 
	 */
	private static final long serialVersionUID = 3362394184109444638L;
	/**
	 * 标签验证的权限值
	 */
	private String standard;
	
	private String standardList;
	
	/**
	 * 验证结果的存储key值
	 */
	static final String CHECK_FLAG = "CHECK_FLAG";
	
	@Override
	public int doStartTag() throws JspException {
		boolean tag = checked(standard, standardList);
		this.setValue(CHECK_FLAG, tag);
		return EVAL_BODY_INCLUDE;
	}
	

	private boolean checked(String standard,String standardList){
		String[] ss =standardList.split(",");
		if(StringUtils.isEmpty(standardList)){
			return false;
		}
		return Arrays.asList(ss).contains(standard);
	}

	public String getStandard() {
		return standard;
	}

	public void setStandard(String standard) {
		this.standard = standard;
	}


	public String getStandardList() {
		return standardList;
	}


	public void setStandardList(String standardList) {
		this.standardList = standardList;
	}

}

加入success对应的实体类，该实体类主要就是对本身的上层标签的值的校验结果进行获取

public class ViewPowerSuccessTag extends TagSupport{
	/**
	 * 
	 */
	private static final long serialVersionUID = -5674428112555303827L;

	@Override
	public int doStartTag() throws JspException {
		boolean tag = (Boolean)((TagSupport)this.getParent()).getValue(ViewPowerChecker.CHECK_FLAG);
		if(tag){
			return EVAL_BODY_INCLUDE;
		}else{
			return SKIP_BODY;
		}
	}
}

而后定义fail 对应的实体类

public class ViewPowerFailTag extends TagSupport{
	/**
	 * 
	 */
	private static final long serialVersionUID = -2700800433218941142L;

	@Override
	public int doStartTag() throws JspException {
		boolean tag = (Boolean)((TagSupport)this.getParent()).getValue(ViewPowerChecker.CHECK_FLAG);
		if(!tag){
			return EVAL_BODY_INCLUDE;
		}else{
			return SKIP_BODY;
		}
	}
}

4.在项目的web.xml文件中定义该标签，这样在该项目的jsp页面就能够使用limit标签了

<jsp-config>
		<taglib>
			 <taglib-uri>limit</taglib-uri>
			 <taglib-location>/WEB-INF/limit-taglib.tld</taglib-location>
		</taglib>
    </jsp-config>

5.使用举例， 如今该jsp页面进行标签引入 <%@ taglib uri="limit" prefix="limit"%>

<limit:checker standard="sendback" standardList="${map.button }">
									<limit:success>
										<button class="inline-block btn2" onclick="backTask()">退回</button>
									</limit:success>
								</limit:checker>

该案例即为使用的limit:checker标签，属性为standard和standardList，经过check对应实例里的方法进行计算，limit：success对其父层标签，即limit：check标签的结果进行分析，若是为true，则显示该标签，若是为false则隐藏该标签. 这些逻辑都清楚的写在这些标签的实体类中