在工程中定义jsp页面可使用的标签

摘要: workorder项目中limit标签的定义和使用

1.我们先引入java.servlet.jsp包。由于是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类似
其中的target-class即为对应的操作实体类，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自己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;
}
}
}

然后定义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页面就可以使用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

<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，通过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，如果为true，则显示该标签，如果为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