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Java接口返回401错误：实战教程，轻松实现无权限访问拦截

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在Java开发中，401错误通常表示客户端未授权，即请求未携带有效的认证信息或者认证信息无效。本文将详细介绍如何在Java接口中返回401错误，并指导你如何轻松实现无权限访问拦截。

一、理解401错误

在HTTP协议中，401错误响应表示请求未授权。当服务器接收到一个请求时，如果发现请求没有携带有效的认证信息，或者认证信息无效，就会返回401错误。

二、Java接口返回401错误

1. 使用Spring框架

如果你使用的是Spring框架，可以通过以下步骤实现401错误的返回：

（1）添加依赖

首先，在你的项目中添加Spring Security依赖。

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
</dependency>

（2）配置Spring Security

在Spring Boot的主类或者配置类中，添加以下代码：

@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .authorizeRequests()
            .anyRequest().authenticated()
            .and()
            .httpBasic();
    }
}

（3）创建认证成功和失败的处理器

@Component
public class CustomAuthenticationEntryPoint implements AuthenticationEntryPoint {
    @Override
    public void commence(HttpServletRequest request, HttpServletResponse response, AuthenticationException authException) throws IOException {
        response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
        response.setContentType("application/json;charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.write("{\"code\":401,\"message\":\"Unauthorized\"}");
        out.flush();
        out.close();
    }
}

@Component
public class CustomAuthenticationFailureHandler implements AuthenticationFailureHandler {
    @Override
    public void onAuthenticationFailure(HttpServletRequest request, HttpServletResponse response, AuthenticationException exception) throws IOException {
        response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
        response.setContentType("application/json;charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.write("{\"code\":401,\"message\":\"Unauthorized\"}");
        out.flush();
        out.close();
    }
}

（4）配置Spring Security

@Override
protected void configure(HttpSecurity http) throws Exception {
    http
        .authorizeRequests()
        .anyRequest().authenticated()
        .and()
        .httpBasic()
        .authenticationEntryPoint(customAuthenticationEntryPoint)
        .authenticationFailureHandler(customAuthenticationFailureHandler);
}

2. 使用Servlet

如果你使用的是Servlet，可以通过以下步骤实现401错误的返回：

（1）创建认证过滤器

public class AuthenticationFilter extends HttpFilter {
    @Override
    protected void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest httpRequest = (HttpServletRequest) request;
        HttpServletResponse httpResponse = (HttpServletResponse) response;
        if (!httpRequest.getMethod().equalsIgnoreCase("OPTIONS")) {
            String token = httpRequest.getHeader("Authorization");
            if (token == null || !token.startsWith("Bearer ")) {
                httpResponse.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
                httpResponse.setContentType("application/json;charset=UTF-8");
                PrintWriter out = httpResponse.getWriter();
                out.write("{\"code\":401,\"message\":\"Unauthorized\"}");
                out.flush();
                out.close();
                return;
            }
        }
        chain.doFilter(request, response);
    }
}

（2）配置过滤器

public class WebFilterConfig implements FilterRegistration.Dynamic {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // ...
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        AuthenticationFilter authenticationFilter = new AuthenticationFilter();
        authenticationFilter.doFilter(request, response, chain);
    }

    @Override
    public void destroy() {
        // ...
    }
}

（3）注册过滤器

WebFilterConfig webFilterConfig = new WebFilterConfig();
FilterRegistration.Dynamic filter = this.getServletContext().addFilter("AuthenticationFilter", webFilterConfig);
filter.addMappingForUrlPatterns(EnumSet.of(DispatcherType.REQUEST), true, "/*");

三、总结

本文介绍了在Java接口中返回401错误的方法，包括使用Spring框架和Servlet。通过以上方法，你可以轻松实现无权限访问拦截。希望本文对你有所帮助！

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