jsp自定义标签2

自定义标签开发步骤

1.1 助手类
1.2 tld
1.3 taglib

数据标签开发一个set标签

开发一个UI标签中的out标签

应用一下,结果如下:

控制标签
开发一个if标签和forEach 标签



select标签

public class SelectTag extends BodyTagSupport {
	
	private String id;
	private String name;
	private List<Object> items = new ArrayList<>();
	private String textKey;
	private String textVal;
	private String selectVal;
	private String headerTextKey;
	private String headerTextVal;
	
	@Override
	public int doStartTag() throws JspException {
		JspWriter out = pageContext.getOut();
			try {
				out.print(toHTML());
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		return super.doStartTag();
	}
	
	
	private String toHTML() throws Exception {
		StringBuffer sb = new StringBuffer();
		sb.append("<select id='"+id+"' name='"+name+"'>");
		if(!(headerTextKey==null || "".equals(headerTextKey)||headerTextVal==null||"".equals(headerTextVal))) {
			sb.append("<option selected value='"+headerTextKey+"'>"+headerTextVal+"</option>");
		}
		String value;
		String html;
		for (Object obj : items) {
			Field textKeyfield = obj.getClass().getDeclaredField(textKey);
			textKeyfield.setAccessible(true);
			value = (String) textKeyfield.get(obj);
			html = (String) PropertyUtils.getProperty(obj, textVal); 
			sb.append("<option value='"+value+"'>"+html+"</option>");
		}
		
		sb.append("</select>");
		return sb.toString();
	}


	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 getSelectVal() {
		return selectVal;
	}
	public void setSelectVal(String selectVal) {
		this.selectVal = selectVal;
	}
	public String getHeaderTextKey() {
		return headerTextKey;
	}
	public void setHeaderTextKey(String headerTextKey) {
		this.headerTextKey = headerTextKey;
	}
	public String getHeaderTextVal() {
		return headerTextVal;
	}
	public void setHeaderTextVal(String headerTextVal) {
		this.headerTextVal = headerTextVal;
	}
	
}

在tld里:

<tag>
    <name>select</name>
    <tag-class>com.jsp.day2.SelectTag</tag-class>
    <body-content>JSP</body-content>
    <attribute>
        <name>id</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
        <name>name</name>
        <required>false</required>
        <rtexprvalue>false</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>false</rtexprvalue>
    </attribute>
    <attribute>
        <name>selectVal</name>
        <required>false</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
    <attribute>
        <name>headerTextKey</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
    <attribute>
        <name>headerTextVal</name>
        <required>false</required>
        <rtexprvalue>false</rtexprvalue>
    </attribute>
  </tag>

如果要默认选中bbb的话,加上这些

if(value.equals(selectVal)) {
				sb.append("<option selected value='"+value+"'>"+html+"</option>");
			}else {
				sb.append("<option value='"+value+"'>"+html+"</option>");
			}