JSP-九大内置对象

pageContext

常用方法

PageContext

abstract public HttpSession getSession();

abstract public Object getPage();

abstract public ServletRequest getRequest();

abstract public ServletResponse getResponse();

abstract public Exception getException();

abstract public ServletConfig getServletConfig();

abstract public ServletContext getServletContext();

abstract public void forward(String relativeUrlPath) throws ServletException, IOException;

abstract public void include(String relativeUrlPath) throws ServletException, IOException;

abstract public void include(String relativeUrlPath, boolean flush) throws ServletException, IOException;

abstract public void handlePageException(Exception e) throws ServletException, IOException;

public BodyContent pushBody() {}

public ErrorData getErrorData() {...}

JspContext

abstract public Object getAttribute(String name); // 返回与页面范围中的名称关联的对象；如果未找到，则返回null

abstract public Object getAttribute(String name, int scope);

abstract public void setAttribute(String name, Object value);

abstract public void setAttribute(String name, Object value, int scope);

abstract public Object findAttribute(String name); // 在页面，请求，会话（如果有效）和应用程序范围内按顺序搜索命名属性，并返回关联的值或null

abstract public void removeAttribute(String name);

abstract public void removeAttribute(String name, int scope);

abstract public int getAttributesScope(String name);

abstract public JspWriter getOut();

public abstract ELContext getELContext();

public JspWriter pushBody( java.io.Writer writer ) {}

public JspWriter popBody() {}

session

application

config

out

page

request

response

exception

存数据

<body>
<%
    pageContext.setAttribute("name1", "value1");
    request.setAttribute("name2", "value2");
    session.setAttribute("name3", "value3");
    application.setAttribute("name4", "value4");
    application.setAttribute("name1", "value11");
%>
<%
    // 从底层到高层寻找，优先用底层同名值
    String name1 = (String) application.getAttribute("name1");
    String name2 = (String) application.getAttribute("name2");
    String name3 = (String) application.getAttribute("name3");
    String name4 = (String) application.getAttribute("name4");
    String name5 = (String) application.getAttribute("name5");
%>
<h1>${name1} + ${pageContext.getAttributesScope("name1")}</h1>
<h1>${name2} + ${pageContext.getAttributesScope("name2")}</h1>
<h1>${name3} + ${pageContext.getAttributesScope("name3")}</h1>
<h1>${name4} + ${pageContext.getAttributesScope("name4")}</h1>
<h1>${name5} + ${pageContext.getAttributesScope("name5")}</h1>
<%=name5%> <%--没有值是会显示null--%>
<h1>${pageScope.get("name1")}</h1>
<h1>${applicationScope.get("name1")}</h1> <%--优先用本作用域里的值--%>
</body>

一个是直接获取，一个从pageContext里拿：

posted @ 2021-01-18 22:55  神乐g  阅读(51)  评论(0)  编辑  收藏  举报