• JSP自定义标签（下）

    hello，家人们，今天我们再来更一节自定义标签的小课堂(●'◡'●)

    目录

    foeach标签

    select标签

    首先，我们还是得先上处理图：

    •   SKIP_BODY：跳过主体（ 不会打印“awa”）
    •   EVAL_BODY_INCLUDE：计算标签主体内容并[输出]（会打印“awa”）
    •   EVAL_PAGE:计算页面的后续部分
    •   SKIP_PAGE:跳过页面的后续部分（不建议用，直接跳过后面全部类容包括body）
    •   EVAL_BODY_AGAIN:再计算主体一次

    常见自定义标签主要步骤：

    • 编写助手类
    • 编写标签库描述文件（tld）
    • 在页面上引入标签使用

    • foeach标签

    1.先new一个cat类

    1. package com.zking.y10.pojo;
    2.  
    3. import java.io.Serializable;
    4.  
    5. public class Cat implements  Serializable{
    6. 	
    7. 	private Integer age;
    8. 	private String name;
    9. 	private String info;
    10. 	
    11. 	public Cat() {
    12. 		// TODO Auto-generated constructor stub
    13. 	}
    14.  
    15. 	
    16. 	
    17. 	public Cat(Integer age, String name, String info) {
    18. 		super();
    19. 		this.age = age;
    20. 		this.name = name;
    21. 		this.info = info;
    22. 	}
    23.  
    24. 	
    25. 	@Override
    26. 	public String toString() {
    27. 		return "Cat [age=" + age + ", name=" + name + ", info=" + info + "]";
    28. 	}
    29.  
    30.  
    31.  
    32. 	public Integer getAge() {
    33. 		return age;
    34. 	}
    35.  
    36.  
    37.  
    38. 	public void setAge(Integer age) {
    39. 		this.age = age;
    40. 	}
    41.  
    42.  
    43.  
    44. 	public String getName() {
    45. 		return name;
    46. 	}
    47.  
    48.  
    49.  
    50. 	public void setName(String name) {
    51. 		this.name = name;
    52. 	}
    53.  
    54.  
    55.  
    56. 	public String getInfo() {
    57. 		return info;
    58. 	}
    59.  
    60.  
    61.  
    62. 	public void setInfo(String info) {
    63. 		this.info = info;
    64. 	}
    65. 	
    66.  
    67. }

    2.定义一个普通类，然后继承BodyTagSupport

    1. package com.zking.y10.dao;
    2.  
    3. import java.util.Iterator;
    4. import java.util.List;
    5. import java.util.Objects;
    6.  
    7. import javax.servlet.jsp.JspException;
    8. import javax.servlet.jsp.tagext.BodyTagSupport;
    9.  
    10. public class FoeachTag extends BodyTagSupport{
    11. 	
    12. 	private List list;
    13. 	private String  var;
    14. 	
    15. 	
    16. 	public void setList(List list) {
    17. 		this.list = list;
    18. 	}
    19. 	public void setVar(String var) {
    20. 		this.var = var;
    21. 	}
    22. 	
    23. 	
    24. 	@Override
    25. 	public int doStartTag() throws JspException {
    26. 		if(Objects.isNull(this.list) || this.list.size()==0) {
    27. 			return SKIP_BODY;
    28. 		}
    29. 		
    30. 		Iterator it=this.list.iterator();
    31. 		Object next = it.next();
    32. 		this.pageContext.setAttribute(var, next);
    33.         this.pageContext.setAttribute("it",it); 
    34. 		return EVAL_BODY_INCLUDE;
    35. 	}
    36. 	
    37. 	
    38. 	
    39. 	@Override
    40. 	public int doAfterBody() throws JspException {
    41. 		Iterator a = (Iterator)this.pageContext.getAttribute("it");
    42. 		if(a.hasNext()) {
    43. 			this.pageContext.setAttribute(var,a.next());
    44. 			 return EVAL_BODY_AGAIN;
    45. 		}
    46. 		
    47. 		return SKIP_BODY;
    48. 	}
    49. 	
    50. }

    3.写一个类，把数据填进去

    1. package com.zking.y10.dao;
    2.  
    3. import java.util.ArrayList;
    4. import java.util.List;
    5.  
    6. import com.zking.y10.pojo.Cat;
    7.  
    8. public class Test {
    9. 	
    10. 	public static List<Cat> getCat(){
    11. 		
    12. 		List<Cat> list=new ArrayList<Cat>();
    13.  
    14. 		Cat c=new Cat();
    15. 		
    16. 		c.setAge(12);
    17. 		c.setName("金渐层");
    18. 		c.setInfo("超可爱噢");
    19. 		
    20.         
    21. 		Cat c1=new Cat();
    22. 		c1.setAge(1);
    23. 		c1.setName("银渐层");
    24. 		c1.setInfo("肥肥胖胖，肉嘟嘟的");
    25. 		
    26. 		
    27. 		Cat c2=new Cat();
    28. 		c2.setAge(10);
    29. 		c2.setName("布偶");
    30. 		c2.setInfo("长毛猫，毛软软的，抱着很舒服");
    31. 		
    32. 		list.add(c);
    33. 		list.add(c1);
    34. 		list.add(c2);
    35. 		
    36. 		return list;
    37. 	}
    38. 		
    39. }

    4.最后再来个index.jsp测试一下

    1.  
    2. <%@page import="com.zking.y10.dao.Test,java.util.List" %>
    3. <%@page import="com.zking.y10.pojo.Cat"%>
    4. <%@page import="java.util.List"%>
    5. <%@ page language="java" contentType="text/html; charset=UTF-8"
    6.     pageEncoding="UTF-8"%>
    7. <%@taglib prefix="p" uri="/zkings" %>   
    8. html>
    9. <html>
    10. <head>
    11. <meta charset="UTF-8">
    12. <title>Insert title heretitle>
    13. head>
    14. <body>
    15.  
    16.  
    17. <%
    18. List<Cat> list=Test.getCat();
    19. request.setAttribute("list",list);
    20. System.out.print(list);
    21. %>
    22. <p:foeach list="${list}" var="l">
    23.  
    24. ${l.age}----${l.name}---${l.info}<br>
    25.  
    26.  
    27. p:foeach>
    28.  
    29. body>
    30. html>

    运行结果：

    • select标签

    1.照常写一个普通类，然后继承BodyTagSupport

    1. package com.zking.y10.dao;
    2.  
    3. import java.util.List;
    4.  
    5. import javax.servlet.jsp.JspException;
    6. import javax.servlet.jsp.JspWriter;
    7. import javax.servlet.jsp.tagext.BodyTagSupport;
    8.  
    9. import org.apache.commons.beanutils.BeanUtils;
    10.  
    11. import com.mysql.jdbc.StringUtils;
    12.  
    13.  
    14. public class SelectTag extends BodyTagSupport{
    15.  
    16. 	private Integer id;
    17. 	
    18. 	private String name;
    19. 	
    20. 	private String clazz;
    21. 	
    22. 	private String Style;
    23. 	
    24. 	private List list;
    25. 	
    26. 	private String value;
    27. 	
    28. 	private String text;
    29. 	
    30. 	private String SelectValue;
    31. 	
    32. 	
    33. 	public SelectTag() {
    34. 		// TODO Auto-generated constructor stub
    35. 	}
    36.  
    37.  
    38. 	public SelectTag(Integer id, String name, String clazz, String style, List list, String value, String text,
    39. 			String selectValue) {
    40. 		super();
    41. 		this.id = id;
    42. 		this.name = name;
    43. 		this.clazz = clazz;
    44. 		Style = style;
    45. 		this.list = list;
    46. 		this.value = value;
    47. 		this.text = text;
    48. 		SelectValue = selectValue;
    49. 	}
    50.  
    51.  
    52. 	
    53.  
    54. 	public void setId(Integer id) {
    55. 		this.id = id;
    56. 	}
    57.  
    58.  
    59. 	public String getName() {
    60. 		return name;
    61. 	}
    62.  
    63.  
    64. 	public void setName(String name) {
    65. 		this.name = name;
    66. 	}
    67.  
    68.  
    69. 	public String getClazz() {
    70. 		return clazz;
    71. 	}
    72.  
    73.  
    74. 	public void setClazz(String clazz) {
    75. 		this.clazz = clazz;
    76. 	}
    77.  
    78.  
    79. 	public String getStyle() {
    80. 		return Style;
    81. 	}
    82.  
    83.  
    84. 	public void setStyle(String style) {
    85. 		Style = style;
    86. 	}
    87.  
    88.  
    89. 	public List getList() {
    90. 		return list;
    91. 	}
    92.  
    93.  
    94. 	public void setList(List list) {
    95. 		this.list = list;
    96. 	}
    97.  
    98.  
    99. 	public String getValue() {
    100. 		return value;
    101. 	}
    102.  
    103.  
    104. 	public void setValue(String value) {
    105. 		this.value = value;
    106. 	}
    107.  
    108.  
    109. 	public String getText() {
    110. 		return text;
    111. 	}
    112.  
    113.  
    114. 	public void setText(String text) {
    115. 		this.text = text;
    116. 	}
    117.  
    118.  
    119. 	public String getSelectValue() {
    120. 		return SelectValue;
    121. 	}
    122.  
    123.  
    124. 	public void setSelectValue(String selectValue) {
    125. 		SelectValue = selectValue;
    126. 	}
    127.  
    128.  
    129. 	
    130. 	
    131. 	
    132. 	@Override
    133. 	public String toString() {
    134. 		return "SelectTag [id=" + id + ", name=" + name + ", clazz=" + clazz + ", Style=" + Style + ", list=" + list
    135. 				+ ", value=" + value + ", text=" + text + ", SelectValue=" + SelectValue + "]";
    136. 	}
    137. 	
    138. 	
    139. 	
    140. 	
    141. 	
    142. 	@Override
    143. 	public int doStartTag() throws JspException {
    144. 		JspWriter out = this.pageContext.getOut();
    145. 		try {
    146. 			String html=getHtml();
    147. 			out.print(html);
    148. 		} catch (Exception e) {
    149. 			e.printStackTrace();
    150. 		}
    151. 		
    152. 		return SKIP_BODY;
    153. 	}
    154. 	
    155. 	
    156. 	
    157. 	public String  getHtml() throws Exception {
    158. 		StringBuilder sb=new StringBuilder();
    159. 		sb.append("");
    160. 		 
    161. 		return sb.toString();
    162. 	}	
    163. }

    2.在后缀名为.tld的文件中增加select标签
         注：tld文件必须保存到WEB-INF目录或其子目录

    1.    
    2.      <tag>
    3.      <name>selectname>
    4.      <tag-class>com.zking.y10.dao.SelectTagtag-class>
    5.      <body-content>jspbody-content>
    6.      <description>select标签description>
    7.      
    8. <attribute>
    9. 			<name>idname>
    10. 			<required>truerequired>
    11. 			<rtexprvalue>falsertexprvalue>
    12. 		attribute>
    13. 		<attribute>
    14. 			<name>namename>
    15. 			<required>truerequired>
    16. 			<rtexprvalue>falsertexprvalue>
    17. 		attribute>
    18. 		<attribute>
    19. 			<name>listname>
    20. 			<required>truerequired>
    21. 			<rtexprvalue>truertexprvalue>
    22. 		attribute>
    23. 		<attribute>
    24. 			<name>clazzname>
    25. 			<required>falserequired>
    26. 			<rtexprvalue>falsertexprvalue>
    27. 		attribute>
    28. 		<attribute>
    29. 			<name>Stylename>
    30. 			<required>falserequired>
    31. 			<rtexprvalue>falsertexprvalue>
    32. 		attribute>
    33. 		<attribute>
    34. 			<name>valuename>
    35. 			<required>truerequired>
    36. 			<rtexprvalue>falsertexprvalue>
    37. 		attribute>
    38. 		<attribute>
    39. 			<name>textname>
    40. 			<required>truerequired>
    41. 			<rtexprvalue>falsertexprvalue>
    42. 		attribute>
    43. 		<attribute>
    44. 			<name>selectValuename>
    45. 			<required>falserequired>
    46. 			<rtexprvalue>falsertexprvalue>
    47. 		attribute>
    48.      
    49.      tag>

    3.测试

    1.  
    2. <%@page import="com.zking.y10.dao.Test,java.util.List" %>
    3. <%@page import="com.zking.y10.pojo.Cat"%>
    4. <%@page import="java.util.List"%>
    5. <%@ page language="java" contentType="text/html; charset=UTF-8"
    6.     pageEncoding="UTF-8"%>
    7. <%@taglib prefix="p" uri="/zkings" %>   
    8. html>
    9. <html>
    10. <head>
    11. <meta charset="UTF-8">
    12. <title>Insert title heretitle>
    13. head> 
    14. <body>
    15.  
    16.  
    17. <%
    18. List<Cat> list=Test.getCat();
    19. request.setAttribute("list",list);
    20.  
    21. %>
    22. <p:foeach list="${list}" var="l">
    23.  
    24. ${l.age}----${l.name}---${l.info}<br>
    25. p:foeach>
    26.  
    27.  
    28. <select id="test" name="test" class="" style="width:100px;">
    29. 		<option value=0>已付款option>
    30. 		<option value= selected>已发货option>
    31. 		<option value=2>已签收option>
    32. 	select>
    33. 	
    34. <p:select name="test" value="age" list="${list}" text="name" id="test" selectValue="3">p:select>
    35.  
    36.  
    37. body>
    38. html>

    4.运行结果：

    今天的简单举例到这里就结束啦~

    今天也要记得微笑呀. 

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  • 原文地址：https://blog.csdn.net/weixin_65975275/article/details/125787212