Define the tags that can be used by jsp pages in the project

1. We first introduce the java.servlet.jsp package. Since it is a maven project, directly import dependencies

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

2. Define the limit-taglib.tld file, which defines the limit tag and sub-tag. When used, limit:checker is similar to the target-class in which is the corresponding operation entity class, and the attribute is the attribute in the entity class.

<!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. Define the corresponding entity class

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;
	}

}

Add the entity class corresponding to success, the entity class is mainly to obtain the verification result of the value of its own upper-level label

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;
		}
	}
}

Then define the entity class corresponding to fail

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. Define this tag in the project's web.xml file, so that the limit tag can be used in the project's jsp page

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

5. Using an example, now the jsp page is tagged with <%@ 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>

This case is the limit:checker tag used. The attributes are standard and standardList. It is calculated by the method in the corresponding instance of check. Limit:success analyzes the result of its parent layer tag, that is, the limit:check tag. If it is true, The label is displayed, if false, the label is hidden. These logics are clearly written in the entity classes of these labels