广告系统开发-通用模块

通用模块

• 通用代码定义、配置定义
• 统一的响应处理
• 统一的异常处理

定义响应模板

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;

//lombok注解
@Data  //相当于setter和getter构造器
@NoArgsConstructor//无参构造器
@AllArgsConstructor//全参构造器
public class CommonResponse<T> implements Serializable {

    private Integer code;
    private String message;
    private T data;

    public CommonResponse(Integer code, String message) {
        this.code = code;
        this.message = message;
    }
}

进行统一响应的拦截

import org.springframework.core.MethodParameter;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.lang.Nullable;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;

//相当于返回json
@RestControllerAdvice
public class CommonResponseDataAdvice implements ResponseBodyAdvice<Object> {

    @Override
    @SuppressWarnings("all")//isAnnotationPresent()方法可能会造成空指针异常，可以将方法的warning隐藏起来
    //通过方法参数或者类参数判断是否支持拦截
    public boolean supports(MethodParameter methodParameter,
                            Class> aClass) {

        //通过方法参数拿到类的声明，类的声明被下面的自定义注解标识，不想受到响应拦截的影响，返回false
        if (methodParameter.getDeclaringClass().isAnnotationPresent(
                IgnoreResponseAdvice.class
        )) {
            return false;
        }
		//方法层面上，同上理解
        if (methodParameter.getMethod().isAnnotationPresent(
                IgnoreResponseAdvice.class
        )) {
            return false;
        }

        return true;
    }

    @Nullable
    @Override
    @SuppressWarnings("all")
    //对CommonResponse进行统一拦截
    public Object beforeBodyWrite(@Nullable Object o,
                                  MethodParameter methodParameter,
                                  MediaType mediaType,
                                  Class> aClass,
                                  ServerHttpRequest serverHttpRequest,
                                  ServerHttpResponse serverHttpResponse) {
		//初始化统一响应的对象
        CommonResponse response = new CommonResponse<>(0, "");
        // o是返回对象，如果为空，直接返回0.
        if (null == o) {
            return response;
        } else if (o instanceof CommonResponse) {
            response = (CommonResponse) o;
        } else {
            response.setData(o);
        }

        return response;
    }
}

自定义注解

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

//表明注解可以作用在类和方法上
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface IgnoreResponseAdvice {
}

统一异常的处理

import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

import javax.servlet.http.HttpServletRequest;

//返回值也是统一响应的类型
@RestControllerAdvice
public class GlobalExceptionAdvice {
	//目标只是AdException类型
    @ExceptionHandler(value = AdException.class)
    //传入两个参数，一个是http请求，一个是自定义异常
    public CommonResponse handlerAdException(HttpServletRequest req,
                                                     AdException ex) {
        CommonResponse response = new CommonResponse<>(-1,
                "business error");
        response.setData(ex.getMessage());
        return response;
    }
}

统一配置

import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

import java.util.List;


@Configuration
public class WebConfiguration implements WebMvcConfigurer {

    @Override
    //参数传进一个有多个http转换器的列表
    public void configureMessageConverters(List>
                                                       converters) {
		//先清空
        converters.clear();
        //将java对象转化成json对象
        converters.add(new MappingJackson2HttpMessageConverter());
    }
}