jsp自定义标签库总结

最新推荐文章于 2022-07-08 08:37:09 发布

Watson4Lin

最新推荐文章于 2022-07-08 08:37:09 发布

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分类专栏： java 文章标签： jsp taglib 自定义标签

本文链接：https://blog.youkuaiyun.com/crazyitlhs/article/details/47018859

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自定义标签主要可以按4个步骤进行开发

1、创建标签的处理类(Tag Handler Class) ，此类需要继承TagSupport类，重写其中的doStartTag()，doEndTag()方法。

/**
 * 
 */
package com.watson.common.taglib;

import java.io.IOException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;

import org.apache.commons.lang3.BooleanUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager;
import org.springframework.web.util.HtmlUtils;
import org.springframework.web.util.JavaScriptUtils;
import org.springframework.web.util.WebUtils;

import com.watson.common.util.ContextUtil;
import com.watson.common.util.LocaleUtil;
import com.watson.common.util.SessionUtil;

/**
 * 多国语言标签
 * @author watson
 * @jsp.tag name="locale" bodycontent="empty"
 */
public class LocaleTag extends TagSupport{

    private static final long serialVersionUID = 5123954502753313916L;

    protected final Log log = LogFactory.getLog(getClass());

    private static boolean isLoad = false;

    private String key = null;

    private String defaultValue = null;
    
    private String args = null;

    private String argTransFlag = null;

    private String characterCoding = null;

    private Boolean htmlEscape=null;//对html特殊字符进行转义
    
    private Boolean javaScriptEscape=null;//对脚本的特殊字符进行处理
    
    private Integer beginIndex=null;//显示字符串开始位置 。
    
    private Integer endIndex=null;//显示字符串结束位置 。
    
    private String implBean = null;

    public LocaleTag(){
    	super();
    	init();
    }
    private void init(){
    	key=defaultValue=args=argTransFlag=characterCoding=null;
    	javaScriptEscape=htmlEscape=null;
    	beginIndex=endIndex=null;
    	implBean = "localeUtil";
    }
    
    @Override
	public void release() {
		super.release();
		init();
	}
    
	/**
     * 获取args
     * @jsp.attribute required="false" rtexprvalue="true"
     * @return
     */
    public String getArgTransFlag() {
        return argTransFlag;
    }

    /**
     * 设置arg翻译,true/false
     * @param args
     */
    public void setArgTransFlag(String argTransFlag) {
        this.argTransFlag = argTransFlag;
    }

    /**
     * 获取args
     * @jsp.attribute required="false" rtexprvalue="true"
     * @return
     */
    public String getArgs() {
        return args;
    }

    /**
     * 设置arg,参数以都好分隔符分割
     * @param args
     */
    public void setArgs(String args) {
        this.args = args;
    }

    /**
     * 獲取語言編碼
     * @jsp.attribute required="true" 
     * @return
     */
    public String getCharacterCoding() {
        return characterCoding;
    }

    public void setCharacterCoding(String characterCoding) {
        this.characterCoding = characterCoding;
    }

    /**
     * 获取键值
     * @jsp.attribute required="true" rtexprvalue="true"
     * @return
     */
    public String getKey() {
        return this.key;
    }

    /**
     * 设置默认值
     * @return
     */
    public String getDefaultValue() {
		return defaultValue;
	}
	public void setDefaultValue(String defaultValue) {
		this.defaultValue = defaultValue;
	}
	public Boolean getHtmlEscape() {
		return htmlEscape;
	}
	public void setHtmlEscape(Boolean htmlEscape) {
		this.htmlEscape = htmlEscape;
	}
	
	public Boolean getJavaScriptEscape() {
		return javaScriptEscape;
	}
	public void setJavaScriptEscape(Boolean javaScriptEscape) {
		this.javaScriptEscape = javaScriptEscape;
	}
	public Integer getBeginIndex() {
		return beginIndex;
	}
	public void setBeginIndex(Integer beginIndex) {
		this.beginIndex = beginIndex;
	}
	public Integer getEndIndex() {
		return endIndex;
	}
	public void setEndIndex(Integer endIndex) {
		this.endIndex = endIndex;
	}
	public String getImplBean() {
        return implBean;
    }

    public void setImplBean(String implBean) {
        this.implBean = implBean;
    }

    /**
     * 设置键值
     * @param key
     */
    public void setKey(String key) {
        try {
            this.key = (String) ExpressionEvaluatorManager.evaluate("key", key, String.class, this, pageContext);
        } catch (JspException e) {
        } catch (NullPointerException e) {
            this.key = "";
        }
    }

    public int doStartTag() throws JspException {
        LocaleUtil localeUtil = (LocaleUtil) ContextUtil.getSpringBeanByName(pageContext.getServletContext(), implBean);
        try {
            if (null == characterCoding) {
                characterCoding = StringUtils.defaultIfBlank(SessionUtil.getLocaleString((HttpServletRequest) pageContext.getRequest()), Constants.DEFAULT_LOCALE);
            }
            String characterValue=null;
            if (StringUtils.isNotEmpty(key)) {
            	defaultValue=StringUtils.isNotBlank( defaultValue )?defaultValue:key;
                if (StringUtils.isNotEmpty(args)) {
                    String[] argList = args.split(",");
                    if ("true".equals(argTransFlag)) {
                        characterValue = localeUtil.getLocalText(characterCoding, key, defaultValue, this.getTrans(argList));
                    } else {
                        characterValue = localeUtil.getLocalText(characterCoding, key, defaultValue, argList);
                    }
                } else {
                    characterValue = localeUtil.getLocalText(characterCoding, key,defaultValue);
                }
            }
            if (StringUtils.isNotEmpty(characterValue)) {
            	characterValue = substring(characterValue,beginIndex,endIndex);
            	if( isHtmlEscape() ){
            		characterValue=HtmlUtils.htmlEscape(characterValue);
            	}
            	if( BooleanUtils.isTrue( javaScriptEscape ) ){
            		JavaScriptUtils.javaScriptEscape( characterValue );
            	}
                pageContext.getOut().print(characterValue);
            }
        } catch (IOException e) {
            log.error(e.getMessage());
        }

        // Continue processing this page
        return SKIP_BODY;
    }

    /***
     * 转义html特殊字符。
     * @return
     */
    protected boolean isHtmlEscape() {
    	Boolean calHtmlEscape=null;
		if (this.htmlEscape != null) {
			calHtmlEscape=this.htmlEscape;
		}else {
			calHtmlEscape= WebUtils.getDefaultHtmlEscape( pageContext.getServletContext() );
		}
		return BooleanUtils.toBoolean( calHtmlEscape );
	}
    
    /***
     * 截取字符串
     * @param input
     * @param beginIndex
     * @param endIndex
     * @return
     */
    protected  String substring(String input, Integer beginIndex, Integer endIndex) {
        if (input == null) input = "";
        if(beginIndex==null && endIndex==null)
        	return input;
        if(beginIndex==null && endIndex!=null )
        	beginIndex=0;
        if(beginIndex!=null && endIndex==null )
        	endIndex=input.length();

        if (beginIndex >= input.length()) return "";
        if (beginIndex < 0) beginIndex = 0;
        if (endIndex < 0 || endIndex > input.length()) endIndex = input.length();
        if (endIndex < beginIndex) return "";
        
        if(input.length()>endIndex){
        	return input.substring(beginIndex, endIndex)+"...";
        }else{
        	return input.substring(beginIndex, endIndex);
        }
    }
    
    private String[] getTrans(String[] arg) {
        LocaleUtil localeUtil = (LocaleUtil) ContextUtil.getSpringBeanByName(pageContext.getServletContext(), implBean);

        String[] ret = new String[arg.length];
        for (int i = 0; i < arg.length; i++) {
            ret[i] = localeUtil.getLocalText(arg[i]);

        }
        return ret;
    }

    public int doEndTag() throws JspException {
    	init();
        return EVAL_PAGE;
    }
}

2、创建标签库描述文件(Tag Library Descrptor File) *.tld文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
    "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">

<taglib>
    <tlib-version>1.0</tlib-version>
    <jsp-version>1.2</jsp-version>
    <short-name>jmoa</short-name>
    <uri>http://www.jmoa.com/tags/jmoa</uri>

    <tag>
        <name>locale</name>
        <tag-class>com.watson.common.taglib.LocaleTag</tag-class>
        <description><![CDATA[国际化配置参数]]></description>
        <attribute>
            <name>key</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>defaultValue</name>
            <required>false</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>args</name>
            <required>false</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>argTransFlag</name>
            <required>false</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>characterCoding</name>
            <required>false</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>htmlEscape</name>
            <required>false</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>javaScriptEscape</name>
            <required>false</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>beginIndex</name>
            <required>false</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>endIndex</name>
            <required>false</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>implBean</name>
            <required>false</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
</taglib>

3、在web.xml文件中配置元素

<jsp-config>
          <taglib>
            <taglib-uri>http://www.jmoa.com/tags/jmoa</taglib-uri>
            <taglib-location>/WEB-INF/jmoa.tld</taglib-location>
          </taglib>

</jsp-config>

4. 在JSP文件中引人标签库

<%@ taglib uri="http://www.jmoa.com/tags/jmoa" prefix="jmoa"%>

注意在开发的过程中可能会遇到一些问题

1.需要导入jsp-api.jar包或者是javaee-api.jar包。但是在tomcat容器中，这两个包是已经存在的，如果将这两个包加入到lib中进行发布，会导致与tomcat中的包冲突，引起jsp解析出现空指针报错。解决此问题的方法是让在两个包只留着开发环境而不需要发布到tomcat中，如果用的是maven构建项目，在引入依赖的时候需要加上包的范围限制

<dependency>
           <groupId>javax</groupId>
           <artifactId>javaee-api</artifactId>
           <version>7.0</version>
           <scope>provided</scope>

</dependency>

或者

<dependency>
           <groupId>javax.servlet.jsp</groupId>
           <artifactId>jsp-api</artifactId>
           <version>2.2</version>
           <scope>provided</scope>
</dependency>

这两个引入其中一个就可以了。