Servlet-异常处理

博客介绍了Servlet抛出异常时的处理方法,可在web.xml中使用error - page元素,指定对特定异常或Http状态码做出相应的Servlet调用,并给出了示例。

①当Servlet抛出一个异常时,在web.xml使用error-page元素指定对特定异常或Http状态码做出相应的Servlet调用

示例:

@WebServlet("/errorHandler")
public class ErrorHandler extends HttpServlet{
    
    @Override
    public void doGet(HttpServletRequest req,HttpServletResponse resp) throws IOException,ServletException {
    resp.setContentType("text/html;charset=UTF-8");
    PrintWriter out = resp.getWriter();
    out.println("<h1>" + "error handler" + "</h1>");
}
    @Override
    public void doPost(HttpServletRequest  request,HttpServletResponse response) throws IOException {
    doGet(request,response);
}

}
<web-app>
    <servlet>
        <servlet-name>errorHandler</servlet-name>
        <servlet-class>com.ryan.biz.ErrorHandler</servlet-class>
    </servlet>   
    <servlet-mapping>
        <servlet-name>errorHandler</servlet-name>
        <url-pattern>/errorHandler</url-pattern>
    </servlet-mapping>

    <error-page>
        <error-code>404</error-code>
        <location>/errorHandler</location>
    </error-page>

    <error-page>
        <error-type>java.io.IOException</error-type>
        <locaton>/errorHandler</location>
    </error-page>

</web-app>

<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" version="4.0"> <display-name>Taobao Data Visualization Platform</display-name> <!-- 配置欢迎页 --> <welcome-file-list> <welcome-file>dashboard.jsp</welcome-file> </welcome-file-list> <!-- 会话Cookie配置 - 解决SameSite警告 --> <session-config> <session-timeout>30</session-timeout> <cookie-config> <http-only>true</http-only> <secure>true</secure> <same-site>None</same-site> <max-age>-1</max-age> </cookie-config> <tracking-mode>COOKIE</tracking-mode> </session-config> <!-- 字符编码过滤器 --> <filter> <filter-name>encodingFilter</filter-name> <filter-class>com.taobao.filter.CharacterEncodingFilter</filter-class> <init-param> <param-name>encoding</param-name> <param-value>UTF-8</param-value> </init-param> </filter> <filter-mapping> <filter-name>encodingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <!-- HotBrandServlet 配置 --> <servlet> <servlet-name>HotBrandServlet</servlet-name> <servlet-class>com.taobao.servlet.HotBrandServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>HotBrandServlet</servlet-name> <url-pattern>/hotbrand</url-pattern> </servlet-mapping> <!-- AgeBehaviorServlet 配置 --> <servlet> <servlet-name>AgeBehaviorServlet</servlet-name> <servlet-class>com.taobao.servlet.AgeBehaviorServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>AgeBehaviorServlet</servlet-name> <url-pattern>/ageBehavior</url-pattern> </servlet-mapping> <!-- ProvincePurchaseServlet 配置 --> <servlet> <servlet-name>ProvincePurchaseServlet</servlet-name> <servlet-class>com.taobao.servlet.ProvincePurchaseServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ProvincePurchaseServlet</servlet-name> <url-pattern>/provincePurchase</url-pattern> </servlet-mapping> <!-- RebuyPredictionServlet 配置 --> <servlet> <servlet-name>RebuyPredictionServlet</servlet-name> <servlet-class>com.taobao.servlet.RebuyPredictionServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>RebuyPredictionServlet</servlet-name> <url-pattern>/rebuyPrediction</url-pattern> </servlet-mapping> <servlet> <servlet-name>UserBehaviorServlet</servlet-name> <servlet-class>com.taobao.servlet.UserBehaviorServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>UserBehaviorServlet</servlet-name> <url-pattern>/userBehavior</url-pattern> </servlet-mapping> <!-- 全局异常处理 --> <error-page> <error-code>404</error-code> <location>/error404.jsp</location> </error-page> <error-page> <error-code>500</error-code> <location>/error500.jsp</location> </error-page> </web-app>怎么改
最新发布
06-17
从错误信息来看,`web.xml` 文件中存在以下问题: 1. **`<same-site>` 标签不被支持**:根据 `cvc-complex-type.2.4.a` 错误提示,`<same-site>` 标签在当前的 XML Schema 中无效。 2. **可能缺少必要的配置项**:例如 `<max-age>` 的值为 `-1` 可能不符合规范。 以下是修复后的 `web.xml` 文件以及相关解释。 --- ### 修复后的 `web.xml` ```xml <?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" version="4.0"> <display-name>Taobao Data Visualization Platform</display-name> <!-- 配置欢迎页 --> <welcome-file-list> <welcome-file>dashboard.jsp</welcome-file> </welcome-file-list> <!-- 会话Cookie配置 - 解决SameSite警告 --> <session-config> <session-timeout>30</session-timeout> <cookie-config> <http-only>true</http-only> <secure>true</secure> <!-- 移除 <same-site> 标签 --> <max-age>-1</max-age> </cookie-config> <tracking-mode>COOKIE</tracking-mode> </session-config> <!-- 字符编码过滤器 --> <filter> <filter-name>encodingFilter</filter-name> <filter-class>com.taobao.filter.CharacterEncodingFilter</filter-class> <init-param> <param-name>encoding</param-name> <param-value>UTF-8</param-value> </init-param> </filter> <filter-mapping> <filter-name>encodingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <!-- HotBrandServlet 配置 --> <servlet> <servlet-name>HotBrandServlet</servlet-name> <servlet-class>com.taobao.servlet.HotBrandServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>HotBrandServlet</servlet-name> <url-pattern>/hotbrand</url-pattern> </servlet-mapping> <!-- AgeBehaviorServlet 配置 --> <servlet> <servlet-name>AgeBehaviorServlet</servlet-name> <servlet-class>com.taobao.servlet.AgeBehaviorServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>AgeBehaviorServlet</servlet-name> <url-pattern>/ageBehavior</url-pattern> </servlet-mapping> <!-- ProvincePurchaseServlet 配置 --> <servlet> <servlet-name>ProvincePurchaseServlet</servlet-name> <servlet-class>com.taobao.servlet.ProvincePurchaseServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ProvincePurchaseServlet</servlet-name> <url-pattern>/provincePurchase</url-pattern> </servlet-mapping> <!-- RebuyPredictionServlet 配置 --> <servlet> <servlet-name>RebuyPredictionServlet</servlet-name> <servlet-class>com.taobao.servlet.RebuyPredictionServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>RebuyPredictionServlet</servlet-name> <url-pattern>/rebuyPrediction</url-pattern> </servlet-mapping> <!-- UserBehaviorServlet 配置 --> <servlet> <servlet-name>UserBehaviorServlet</servlet-name> <servlet-class>com.taobao.servlet.UserBehaviorServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>UserBehaviorServlet</servlet-name> <url-pattern>/userBehavior</url-pattern> </servlet-mapping> <!-- 全局异常处理 --> <error-page> <error-code>404</error-code> <location>/error404.jsp</location> </error-page> <error-page> <error-code>500</error-code> <location>/error500.jsp</location> </error-page> </web-app> ``` --- ### 给出解释 #### 1. **移除 `<same-site>` 标签** - `<same-site>` 标签不是标准的 `web.xml` 配置项。如果需要设置 `SameSite` 属性,可以通过 Servlet 或过滤器动态设置响应头。例如: ```java response.setHeader("Set-Cookie", "JSESSIONID=" + session.getId() + "; Secure; HttpOnly; SameSite=None"); ``` #### 2. **保留 `<max-age>` 标签** - `<max-age>` 是有效的配置项,但其值为 `-1` 表示 Cookie 不会过期(会话级 Cookie)。如果需要调整 Cookie 的生命周期,可以将其设置为正整数(单位为秒)。 #### 3. **确保 XML Schema 合规** - 使用正确的 `xsi:schemaLocation` 和 `version` 声明,确保文件符合 Java EE 4.0 规范。 #### 4. **其他配置保持不变** - 过滤器、Servlet 和全局异常处理配置无需修改,直接保留原样。 --- ###
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