如何生成“返回搜索结果” url 通过 JSTL 或 JSP 中的自定义 lib 包含所有参数并指定排除参数？

Question

我想在 JSP 中生成“返回搜索结果”URL。我使用 JSTL taglib 并且它有效：

<c:url var="backUrl" value="list.html">
    <c:forEach items="${param}" var="currentParam">
        <c:param name="${currentParam.key}" value="${currentParam.value}"/>
    </c:forEach>
</c:url>
<a href="${backUrl}">&lt; return to search results / list</a>

我想要一个更好的解决方案，例如自定义库来使用一行代码生成反向链接，例如：

<tagname:url var="backUrl" value="list.html" includeAllParams="true" excludeParams="id, question"/>
<a href="${backUrl}">&lt; return to search results / list</a>

因为，我想通过排除参数重新使用此代码：

<c:url var="backUrl" value="list.html">    
    <c:forEach items="${param}" var="currentParam">
        <c:if test="${currentParam.key ne 'id'}">
            <c:param name="${currentParam.key}" value="${currentParam.value}"/>
        </c:if>
    </c:forEach>
</c:url>
<a href="${backUrl}">&lt; return to search results / list</a>

我的问题最佳实践是什么以及如何创建自定义库来通过一行生成链接：

<tagname:url var="backUrl" value="list.html" includeAllParams="true" excludeParams="id, question"/>

谢谢。

Answer 1

好的，我创建了一个自定义选项卡：

Class:

package com.test;
import java.util.Collections;
import java.util.Enumeration;
import java.util.List;    
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspException;    
import org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager;
import org.apache.taglibs.standard.tag.el.core.UrlTag;

public class CustomUrlTag extends UrlTag {

    private static final long serialVersionUID = 1L;    
    private String includeAllParams;    
    private String excludeParams;

    public CustomUrlTag() {
        init();
    }

    @Override
    public int doStartTag() throws JspException {
        return super.doStartTag();
    }

    @Override
    public int doEndTag() throws JspException {

        if (isIncludeAllParam()) {

          final HttpServletRequest request = (HttpServletRequest) this.pageContext.getRequest();

          // iterate over request parameters
          final List<String> requestParameterNames = Collections.list((Enumeration<String>) request.getParameterNames());

          // exclude parameters
          if (null != excludeParams) {
              for (final String currentExcludeParam : excludeParams.split("[,]")) {
                  requestParameterNames.remove(currentExcludeParam);
              }
          }

          for (final String parameterName : requestParameterNames) {
              // add parameters
              addParameter(parameterName, request.getParameter(parameterName));
          }
        }
        return super.doEndTag();
    }

    @Override
    public void release() {
        super.release();
        init();
    }

    private void init() {
        includeAllParams = null;
    }

    private boolean isIncludeAllParam() throws JspException {
        final Object r = ExpressionEvaluatorManager.evaluate("includeAllParams", includeAllParams,
                java.lang.Boolean.class, this, pageContext);
        if (r != null) {
            return ((Boolean) r).booleanValue();
        }
        return false;
    }

    public void setIncludeAllParams(String includeAllParams) {
        this.includeAllParams = includeAllParams;
    }

    public void setExcludeParams(String excludeParams) {
        this.excludeParams = excludeParams;
    }
}

tld:

<tag>
        <description>
            Creates a URL with optional query parameters.
        </description>
        <name>customUrl</name>
        <tag-class>com.test.CustomUrlTag</tag-class>
        <body-content>JSP</body-content>
        <attribute>
            <description>
                Name of the exported scoped variable for the
                processed url. The type of the scoped variable is
                String.
            </description>
            <name>var</name>
            <required>false</required>
            <rtexprvalue>false</rtexprvalue>
        </attribute>
        <attribute>
            <description>URL to be processed.</description>
            <name>value</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>    
        <attribute>
            <description></description>
            <name>includeAllParams</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>    
        <attribute>
            <description></description>
            <name>excludeParams</name>
            <required>false</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>

并在 jsp 中：

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

<thePrefix:customUrl var="backUrl" value="list.html" includeAllParams="true" excludeParams="id"/>