标签:span ESS 一个 oaf uid false selected lan serial
当jsp的内置标签和jstl标签库内的标签都满足不了需求,这时候就需要开发者自定义标签。
1 创建一个标签助手类(继承BodyTagSupport)
标签属性必须助手类的属性对应、且要提供对应get/set方法rtexprvalue
2 在你的web应用目录下,找到WEB-INF文件夹,在里面新建一个tld类型的文件
如果你忘记了怎么写,可以参考jstl里的tld文件,如下:
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN" "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd"> <!-- 标签库描述符 --> <taglib xmlns="http://java.sun.com/JSP/TagLibraryDescriptor"> <!-- 代表标签库的版本号 --> <tlib-version>1.0</tlib-version> <!-- 代表jsp的版本 --> <jsp-version>1.2</jsp-version> <!-- 你的标签库的简称 --> <short-name>test</short-name> <!-- 你标签库的引用uri --> <uri>/zking</uri> <tag> <!-- 标签名 --> <name>yy</name> <!-- 标签工具类 --> <tag-class>com.TestTag</tag-class> <!-- 标签的内容类型:empty表示空标签,jsp表示可以为任何合法的JSP元素 --> <body-content>jsp</body-content> <!-- 自定义标签的属性定义,请注意一定要在标签类中提供对应的get/set方法 --> <attribute> <!-- 自定义标签的属性名称 --> <name>name</name> <!-- true表示必填 --> <required>true</required> <!-- true支持动态值,可以向值里面填jsp表达式、EL表达式,false则不支持 --> <rtexprvalue>false</rtexprvalue> </attribute> </tag> </taglib>
3在JSP通过taglib指令导入标签库,并通过指定后缀访问自定义标签
分别创建一个·set和out的助手类
1.set
package com.jsp;
import javax.servlet.jsp.JspException; import javax.servlet.jsp.tagext.BodyTagSupport; public class SetTag extends BodyTagSupport{ private static final long serialVersionUID = 1L; private String var; private Object value; 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; } @Override public int doStartTag() throws JspException { pageContext.setAttribute(var, value);//将值存入pageContext return SKIP_BODY; }
2.out
package com.jsp; import java.io.IOException; import javax.servlet.jsp.JspException; import javax.servlet.jsp.JspWriter; import javax.servlet.jsp.tagext.BodyTagSupport; public class OutTag extends BodyTagSupport { private static final long serialVersionUID = 5811663341301161566L; private String value; public String getValue() { return value; } public void setValue(String value) { this.value = value; } @Override public int doStartTag() throws JspException { JspWriter out = pageContext.getOut(); try { out.print(value); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return SKIP_BODY; } }
在tld文件中添加set和out的标签
<tag> <name>set</name> <tag-class>com.jsp.SetTag</tag-class> <body-content>JSP</body-content> <attribute> <name>var</name> <required>true</required> <rtexprvalue>false</rtexprvalue> </attribute> <attribute> <name>value</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> </tag> <tag> <name>out</name> <tag-class>com.jsp.OutTag</tag-class> <body-content>JSP</body-content> <attribute> <name>value</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> </tag>
jsp页面演示set,out标签
<z:set var="name" value="hello"></z:set> <z:out value="${name }"></z:out>
步骤同上:
package com.jsp.jsp; /* * if助手类 */ import javax.servlet.jsp.JspException; import javax.servlet.jsp.tagext.BodyTagSupport; public class IfTag extends BodyTagSupport{ private boolean test; public boolean isTest() { return test; } public void setTest(boolean test) { this.test = test; } @Override public int doStartTag() throws JspException { if(!test) { return SKIP_BODY;//不显示标签中间的内容 } return EVAL_BODY_INCLUDE;//显示标签中间的内容 } }
<tag> <name>if</name> <tag-class>com.jsp.IfTag</tag-class> <body-content>JSP</body-content> <attribute> <name>test</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> </tag>
jsp页面演示:
<c:if test="true" >你看得见我</c:if> <c:if test="false">你看不见我</c:if>
package com.jsp; /** * foreach助手类 */ import java.util.ArrayList; import java.util.Iterator; import java.util.List; import javax.servlet.jsp.JspException; import javax.servlet.jsp.tagext.BodyTagSupport; public class ForeachTag extends BodyTagSupport { private static final long serialVersionUID = -6290285418914929131L; private String var; private List<Object> items = new ArrayList<>(); 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; } @Override public int doStartTag() throws JspException { if (items == null || items.size() == 0) { return SKIP_BODY; } else { Iterator<Object> it = items.iterator(); // 作用域进行传递 pageContext.setAttribute("it", it); // 第一次给变量进行赋值 pageContext.setAttribute(var, it.next()); return EVAL_BODY_INCLUDE; } } @Override public int doAfterBody() throws JspException { // TODO Auto-generated method stub Iterator<Object> its = (Iterator<Object>) pageContext.getAttribute("it"); while (its.hasNext()) { // 将循环读取出来的数据显示在界面上 pageContext.setAttribute(var, its.next()); return EVAL_BODY_AGAIN; } return SKIP_BODY; } }
<tag> <name>foreah</name> <tag-class>com.jsp.ForeachTag</tag-class> <body-content>JSP</body-content> <attribute> <name>var</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> <attribute> <name>items</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> </tag>
jsp页面演示foreach标签
<% List<String> is = new ArrayList<>(); is.add("aa"); is.add("bb"); is.add("cc"); is.add("dd"); is.add("sb"); pageContext.setAttribute("is", is); %> <ol> <z:foreah items="${is }" var="i"> <li>${i }</li> </z:foreah> </ol>
JSP自定义select标签
创建一个学生类
package com.entity; 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(); // TODO Auto-generated constructor stub } }
package com.jsp; import java.io.IOException; import java.lang.reflect.Field; import java.util.ArrayList; import java.util.List; import javax.servlet.jsp.JspException; import javax.servlet.jsp.JspWriter; import javax.servlet.jsp.tagext.BodyTagSupport; import org.apache.commons.beanutils.BeanUtils; public class SelectTag extends BodyTagSupport { private static final long serialVersionUID = 1L; private String id; private String name; private List<Object> items = new ArrayList<Object>(); private String textKey; private String textval; private String headTextKey; private String headTextVal; private String selectedval; 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 getHeadTextKey() { return headTextKey; } public void setHeadTextKey(String headTextKey) { this.headTextKey = headTextKey; } public String getHeadTextVal() { return headTextVal; } public void setHeadTextVal(String headTextVal) { this.headTextVal = headTextVal; } public String getSelectedval() { return selectedval; } public void setSelectedval(String selectedval) { this.selectedval = selectedval; } @Override public int doStartTag() throws JspException { JspWriter out = pageContext.getOut(); try { out.write(toHTML()); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } return super.doStartTag(); } /** * 拼接出下拉列表所对应的select的html代码 * <select id=‘‘ name=‘‘> * <option value=‘-1‘selected>=======请选择======</option> * </select> */ private String toHTML() throws Exception { StringBuilder sb = new StringBuilder(); sb.append("<select id=‘" + id + "‘ name=‘" + name + "‘>"); if (headTextKey == null || "".equals(headTextKey) || headTextVal == null || "".equals(headTextVal)) { sb.append("<option value=‘" + headTextKey + "‘ selected>" + headTextVal + "</option>"); } String val; String html; for (Object obj : items) { // 要让学生的id存入数据库,让学生的名字展示在jsp页面 // <option value=‘s001‘>ls</option> // obj sid sname Field textKeyField = obj.getClass().getDeclaredField(textKey); textKeyField.setAccessible(true); val = (String) textKeyField.get(obj); html = BeanUtils.getProperty(obj, textval); if(val.equals(selectedval)) { sb.append(" <option value=‘"+val+"‘selected>"+html+"</option>"); }else { sb.append("<option value=‘"+val+"‘>"+html+"</option>"); } } sb.append("</select>"); return sb.toString(); } }
select标签的tld文件
<tag> <name>select</name> <tag-class>com.jsp.ServletTag</tag-class> <body-content>JSP</body-content> <attribute> <name>id</name> <required>false</required> <rtexprvalue>flase</rtexprvalue> </attribute> <attribute> <name>name</name> <required>flase</required> <rtexprvalue>flase</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>flase</rtexprvalue> </attribute> <attribute> <name>headTextKey</name> <required>false</required> <rtexprvalue>false</rtexprvalue> </attribute> <attribute> <name>headTextVal</name> <required>false</required> <rtexprvalue>flase</rtexprvalue> </attribute> <attribute> <name>selectedval</name> <required>false</required> <rtexprvalue>true</rtexprvalue> </attribute> </tag>
<% List<Student> student=new ArrayList(); student.add(new Student("1","zs")); student.add(new Student("2","ls")); student.add(new Student("3","ww")); student.add(new Student("4","zl")); student.add(new Student("5","qq")); student.add(new Student("6","gd")); student.add(new Student("7","wb")); pageContext.setAttribute("stus", student); %> <p:select items="${stus }" textval="sname" textKey="sid"></p:select> <p:select headTextKey="-1" headTextVal="===请选择学生===" items="${stus }" textval="sname" textKey="sid"></p:select>
标签:span ESS 一个 oaf uid false selected lan serial
原文地址:https://www.cnblogs.com/huxiaocong/p/11059697.html