multithreading - 自定义 JSP 标签是否被多线程访问

Question

我有一个简单的自定义 JSP 标记，定义如下:

public class SimpleTag extends TagSupport {
    private static final long serialVersionUID = 1L;

    private String var;
    private Map<String, String> data = new HashMap<String, String>();

    public String getVar() {
        return var;
    }

    public void setVar(String var) {
        this.var = var;
    }

    @Override
    public int doStartTag() throws JspException {
        populateData();
        pageContext.setAttribute(var, data);
        return EVAL_BODY_INCLUDE;
    }

    @Override
    public int doEndTag() throws JspException {
        pageContext.setAttribute(var, null);
        return EVAL_PAGE;
    }

    private void populateData() {
        // add data to "data" map
    }
}

我将 hashmap 暴露给标签体。

标签会被容器重用(缓存/池化)还是被多线程访问？我需要在标签设计中格外小心吗？

如果它太基础了，我深表歉意。我的搜索一直没有成功。提前致谢。

Answer 1

Classic Tag Handlers 可以合并或不合并，具体取决于容器；
根据规范 (http://download.oracle.com/otn-pub/jcp/jsp-2_3-mrel2-eval-spec/JSP2.3MR.pdf)

，无法合并简单标签处理程序

但无论如何，不​​应该有任何线程问题，因为处理程序应该一次只处理一个请求:

Clarify that a tag handler instance is actively processing only one request at a time; this happens naturally if the tag handler is instantiated afresh through new() invocations, but it requires spelling once tag handler pooling is introduced. This clarification affected Chapter JSP.13.