SpringBoot（4）SpringBoot中使用@WebFilter转发&重定向失败的解决方案

结论

• 加return关键字可以使过滤器中的转发&重定向提交

问题复现

现象1【转发】

过滤器代码

@WebFilter(urlPatterns= {"/aaa"})
public class testFilter implements Filter {

	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		HttpServletRequest request1 =(HttpServletRequest) request;
		HttpServletResponse response1 =(HttpServletResponse) response;

		System.out.println("111111111666666666666666666666666666666666");
		request1.getRequestDispatcher("index").forward(request1,response1);//正确的写法=》前缀+index+后缀=》/templates/index.html
		System.out.println("11111111177777777777777777777777777777777777");

		System.out.println("111111111222222222222222222222");
		chain.doFilter(request1, response1);
		System.out.println("1111111113333333333333333333333");
	}
}

结果

• 页面正常转发，但是控制台报错

• java.lang.IllegalStateException: Cannot call sendError() after the response has been committed

• chain.doFilter之后的代码不会被执行
  执行完 chain.doFilter之后，过滤器放行
  

解决方案

• 在转发后面添加return，但是return之后，不能再添加其他代码，不然会编译报错
• 可以使用if-else格式处理return

@WebFilter(urlPatterns= {"/aaa"})
public class testFilter implements Filter {

	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		HttpServletRequest request1 =(HttpServletRequest) request;
		HttpServletResponse response1 =(HttpServletResponse) response;

		System.out.println("111111111666666666666666666666666666666666");
		request1.getRequestDispatcher("index").forward(request1,response1);//正确的写法=》前缀+index+后缀=》/templates/index.html
		System.out.println("11111111177777777777777777777777777777777777");
		return;
	}
}

现象2【重定向】

过滤器代码

@WebFilter(urlPatterns= {"/aaa"})
public class testFilter implements Filter {
	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		HttpServletRequest request1 =(HttpServletRequest) request;
		HttpServletResponse response1 =(HttpServletResponse) response;
		
		System.out.println("1111111114444444444444444444444444");
		response1.sendRedirect("/user/showLogin");
		System.out.println("1111111115555555555555555555555555555");

		System.out.println("111111111222222222222222222222");
		chain.doFilter(request1, response1);
		System.out.println("1111111113333333333333333333333");
	}
}

结果

• 页面不能正常重定向
• java.lang.IllegalStateException: Cannot call sendError() after the response has been committed
  

解决方案

• 加return

@WebFilter(urlPatterns= {"/aaa"})
public class testFilter implements Filter {
	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		HttpServletRequest request1 =(HttpServletRequest) request;
		HttpServletResponse response1 =(HttpServletResponse) response;

		System.out.println("1111111114444444444444444444444444");
		response1.sendRedirect("/user/showLogin");
		return;//添加return之后就可以重定向了（相当于flush提交）
	}
}