关于Controller 层返回值的公共包装类的问题

时间：2022-11-22 10:56:38|栏目：JAVA代码|点击：次

场景：在微服务中，一般返回数据都会有个返回码、返回信息和返回消息体，但是每次返回时候调用或者是封装，太过麻烦，有没有什么办法不用每次都封装呢？

答案是有的。

返回值对象 ResponseData

package com.study.auth.comm;
 
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.annotation.JSONField;
import com.alibaba.fastjson.serializer.SerializerFeature;
 
import java.io.Serializable;
 
/**
 * @Package: com.study.auth.comm
 * @Description: <返回数据>
 * @Author: MILLA
 * @CreateDate: 2018/4/8 9:10
 * @UpdateUser: MILLA
 * @UpdateDate: 2018/4/8 9:10
 * @Version: 1.0
 */
public final class ResponseData<T> implements Serializable {
    private static final long serialVersionUID = 7824278330465676943L;
 
    private static final String SUCCESS_CODE = "1000";
 
    private static final String SUCCESS_MSG = "success";
    /**
     * 响应编码
     */
    @JSONField(serialzeFeatures = {SerializerFeature.WriteMapNullValue}, ordinal = 1)
    private String code;
 
    /**
     * 响应提示
     */
    @JSONField(serialzeFeatures = {SerializerFeature.WriteMapNullValue}, ordinal = 2)
    private String msg;
 
    /**
     * 返回的数据
     */
    @JSONField(serialzeFeatures = {SerializerFeature.WriteMapNullValue}, ordinal = 10)
    private T data;
 
    public static ResponseData success() {
        return initData(SUCCESS_CODE, SUCCESS_MSG, null);
    }
 
    public static ResponseData error(String code) {
        String msg = PropertiesReaderUtil.getProperty(code, null);
        return initData(code, msg, null);
    }
 
    public static ResponseData error(String code, String msg) {
        return initData(code, msg, null);
    }
 
    public static <T> ResponseData success(T t) {
        return initData(SUCCESS_CODE, SUCCESS_MSG, t);
    }
 
    public static <T> ResponseData errorData(String code, T data) {
        String msg = PropertiesReaderUtil.getProperty(code, null);
        return initData(code, msg, data);
    }
 
    public static <T> ResponseData errorData(String code, String msg, T data) {
        return initData(code, msg, data);
    }
 
    private static <T> ResponseData initData(String code, String msg, T t) {
        ResponseData data = new ResponseData(SUCCESS_CODE);
        if (!isBlank(msg)) {
            data.setMsg(msg);
        }
        if (!isBlank(code)) {
            data.setCode(code);
        }
        if (t != null) {
            data.setData(t);
        }
        return data;
    }
 
    private static boolean isBlank(CharSequence cs) {
        int strLen;
        if (cs != null && (strLen = cs.length()) != 0) {
            for (int i = 0; i < strLen; ++i) {
                if (!Character.isWhitespace(cs.charAt(i))) {
                    return false;
                }
            }
            return true;
        } else {
            return true;
        }
    }
 
    public ResponseData() {
    }
 
    public ResponseData(String code) {
        this.code = code;
    }
 
    public String getCode() {
        return code;
    }
 
    public void setCode(String code) {
        this.code = code;
    }
 
    public String getMsg() {
        return msg;
    }
 
    public void setMsg(String msg) {
        this.msg = msg;
    }
 
    public T getData() {
        return data;
    }
 
    public void setData(T data) {
        this.data = data;
    }
 
    @Override
    public String toString() {
        return JSON.toJSONString(this);
    }
}

如上图的包装，还是太繁琐了。

装饰者模式使用-增强类InitializingAdviceDecorator
通过实现InitializingBean和装饰者模式对Controller层的返回值进行包装，大致思路：
通过RequestMappingHandlerAdapter获取所有的返回值处理对象HandlerMethodReturnValueHandler创建一个新的集合存储上一步获取的集合（因为上一步的结果是unmodifiableList类型的）遍历该集合找到HandlerMethodReturnValueHandler对象，将这个位置的handler替换程自定义的handler将新获到的集合重新设置到RequestMappingHandlerAdapter的setReturnValueHandlers方法中

package com.study.auth.config;
 
import com.study.auth.comm.ResponseData;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.MethodParameter;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.method.support.ModelAndViewContainer;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;
import org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor;
 
import java.util.ArrayList;
import java.util.List;
 
/**
 * @Package: com.study.auth.config.core
 * @Description: <增强controller层返回值>
 * @Author: milla
 * @CreateDate: 2020/09/04 14:42
 * @UpdateUser: milla
 * @UpdateDate: 2020/09/04 14:42
 * @UpdateRemark: <>
 * @Version: 1.0
 */
@Configuration
public class InitializingAdviceDecorator implements InitializingBean {
    @Autowired
    private RequestMappingHandlerAdapter adapter;
 
    @Override
    public void afterPropertiesSet() {
        //获取所有的handler对象
        List<HandlerMethodReturnValueHandler> returnValueHandlers = adapter.getReturnValueHandlers();
        //因为上面返回的是unmodifiableList，所以需要新建list处理
        List<HandlerMethodReturnValueHandler> handlers = new ArrayList(returnValueHandlers);
        this.decorateHandlers(handlers);
        //将增强的返回值回写回去
        adapter.setReturnValueHandlers(handlers);
    }
 
 
    /**
     * 使用自定义的返回值控制类
     *
     * @param handlers
     */
    private void decorateHandlers(List<HandlerMethodReturnValueHandler> handlers) {
        for (HandlerMethodReturnValueHandler handler : handlers) {
            if (handler instanceof RequestResponseBodyMethodProcessor) {
                //找到返回值的handler并将起包装成自定义的handler
                ControllerReturnValueHandler decorator = new ControllerReturnValueHandler((RequestResponseBodyMethodProcessor) handler);
                int index = handlers.indexOf(handler);
                handlers.set(index, decorator);
                break;
            }
        }
    }
 
    /**
     * 自定义返回值的Handler
     * 采用装饰者模式
     */
    private class ControllerReturnValueHandler implements HandlerMethodReturnValueHandler {
        //持有一个被装饰者对象
        private HandlerMethodReturnValueHandler handler;
 
        ControllerReturnValueHandler(RequestResponseBodyMethodProcessor handler) {
            this.handler = handler;
        }
 
        @Override
        public boolean supportsReturnType(MethodParameter returnType) {
            return true;
        }
 
        /**
         * 增强被装饰者的功能
         *
         * @param returnValue  返回值
         * @param returnType   返回类型
         * @param mavContainer view
         * @param webRequest   请求对象
         * @throws Exception 抛出异常
         */
        @Override
        public void handleReturnValue(Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
            //如果已经封装了结构体就直接放行
            if (returnValue instanceof ResponseData) {
                handler.handleReturnValue(returnValue, returnType, mavContainer, webRequest);
                return;
            }
            //正常返回success
            ResponseData success = ResponseData.success(returnValue);
            handler.handleReturnValue(success, returnType, mavContainer, webRequest);
        }
    }
}

配置文件读取类PropertiesReaderUtil

package com.study.auth.comm;
 
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
 
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Properties;
 
/**
 * @Package: com.milla.navicat.comm
 * @Description: <读取配置properties工具类>
 * @Author: MILLA
 * @CreateDate: 2018/8/10 10:30
 * @UpdateUser: MILLA
 * @UpdateDate: 2018/8/10 10:30
 * @UpdateRemark: <>
 * @Version: 1.0
 */
public final class PropertiesReaderUtil {
    private static final String ENCODING = "UTF-8";
    private static final Logger logger = LoggerFactory.getLogger(PropertiesReaderUtil.class);
    private static Properties propsZH;
    private static Properties propsCN;
    private static String name = null;
 
    static {
        //加载英文
        //loadProps(false);
        //加载中文
        loadProps(true);
    }
 
    /**
     * 第一种，通过类加载器进行获取properties文件流
     * 第二种，通过类进行获取properties文件流
     * in = PropertyUtil.class.getResourceAsStream("/properties/message_ZH.properties");
     * in = PropertiesReaderUtil.class.getClassLoader().getResourceAsStream("properties/message_ZH.properties");
     */
    synchronized static private void loadProps(boolean isZh) {
        logger.debug("start loading properties");
        InputStream in = null;
        if (isZh) {
            propsZH = new Properties();
            name = "properties/message_ZH.properties";
            in = PropertiesReaderUtil.class.getClassLoader().getResourceAsStream(name);
        } else {
            propsCN = new Properties();
            name = "properties/message_EN.properties";
            in = PropertiesReaderUtil.class.getClassLoader().getResourceAsStream(name);
        }
        try {
            if (isZh) {
                propsZH.load(new InputStreamReader(in, ENCODING));
            } else {
                propsCN.load(new InputStreamReader(in, ENCODING));
            }
        } catch (Exception e) {
            logger.debug("loading properties error :{}", e);
        } finally {
            try {
                if (null != in) {
                    in.close();
                }
            } catch (IOException e) {
                logger.debug("closing properties io error :{}", e);
            }
        }
    }
 
    public static String getProperty(String key) {
        return getPropertyZH(key);
    }
 
    public static String getProperty(String key, String defaultValue) {
        return getPropertyZH(key, defaultValue);
    }
 
    public static String getPropertyZH(String key) {
        if (null == propsZH) {
            loadProps(true);
        }
        return propsZH.getProperty(key);
    }
 
    public static String getPropertyZH(String key, String defaultValue) {
        if (null == propsZH) {
            loadProps(true);
        }
        return propsZH.getProperty(key, defaultValue);
    }
 
    public static String getPropertyCN(String key) {
        if (null == propsCN) {
            loadProps(false);
        }
        return propsCN.getProperty(key);
    }
 
    public static String getPropertyCN(String key, String defaultValue) {
        if (null == propsCN) {
            loadProps(false);
        }
        return propsCN.getProperty(key, defaultValue);
    }
}

配置文件message_ZH.properties
路径为：properties/message_ZH.properties

也可添加国家化英文或者是其他语言配置

1001=用户未登录
#====非业务返回码=========
1100=服务器内部错误
1101=空指针异常
1102=数据类型转换异常
1103=IO异常
1104=该方法找不到异常
1105=数组越界异常
1106=请求体缺失异常
1107=类型匹配异常
1108=请求参数缺失异常
1109=请求方法不支持异常
1110=请求头类型不支持异常
1111=参数解析异常
1112=必要参数不能为空
#=======================

统一异常捕捉类RestfulExceptionHandler
此时，基本能保证增强Controller层的返回值了，如果有需要的话，可能通过@RestControllerAdvice注解，针对抛出的异常使用返回值对象进行包装

package com.study.auth.exception;
 
import com.alibaba.fastjson.JSONException;
import com.study.auth.comm.PropertiesReaderUtil;
import com.study.auth.comm.ResponseData;
import com.study.auth.constant.CommonConstant;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.TypeMismatchException;
import org.springframework.boot.json.JsonParseException;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.web.HttpMediaTypeNotSupportedException;
import org.springframework.web.HttpRequestMethodNotSupportedException;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.MissingServletRequestParameterException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestControllerAdvice;
 
import javax.security.auth.login.AccountException;
import java.io.IOException;
import java.sql.SQLException;
 
/**
 * @Package: com.study.auth.exception
 * @Description: <所有异常拦截类>
 * @Author: milla
 * @CreateDate: 2020/09/04 15:35
 * @UpdateUser: milla
 * @UpdateDate: 2020/09/04 15:35
 * @UpdateRemark: <>
 * @Version: 1.0
 */
@Slf4j
@RestControllerAdvice
public class RestfulExceptionHandler {
    private ResponseData responseData(String code, Exception e) {
        log.error("异常代码:{},异常描述:{},异常堆栈:", code, PropertiesReaderUtil.getProperty(code), e);
        return ResponseData.error(code);
    }
 
    private ResponseData<String> responseData(String code, String message, Exception e) {
        log.error("异常代码:{},异常描述:{},异常堆栈:", code, message, e);
        return ResponseData.error(code, message);
    }
 
    /**
     * 运行时异常
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler(Exception.class)
    public ResponseData runtimeExceptionHandler(Exception e) {
        return responseData(CommonConstant.EX_RUN_TIME_EXCEPTION, e);
    }
 
    /**
     * 处理SQLSyntaxErrorException
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler(SQLException.class)
    public ResponseData<String> sqlException(SQLException e) {
        return responseData(CommonConstant.EX_RUN_TIME_EXCEPTION, e.getMessage(), e);
    }
 
 
    /**
     * 处理CustomerMessageException
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler(CustomMessageException.class)
    public ResponseData<String> customerMessageException(CustomMessageException e) {
        return responseData(CommonConstant.EX_RUN_TIME_EXCEPTION, e.getMessage(), e);
    }
 
    /**
     * 处理AccountException
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler(AccountException.class)
    public ResponseData<String> accountException(AccountException e) {
        return responseData(e.getMessage(), e);
    }
 
 
    //---------------------------------------jdk/spring自带的异常----------------------------------
 
    /**
     * 处理IllegalArgumentException
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler(IllegalArgumentException.class)
    public ResponseData<String> illegalArgumentException(IllegalArgumentException e) {
        return responseData(CommonConstant.EX_RUN_TIME_EXCEPTION, e.getMessage(), e);
    }
 
    /**
     * 空指针异常
     *
     * @param e 异常
     * @return
     */
    @ResponseStatus
    @ExceptionHandler(NullPointerException.class)
    public ResponseData nullPointerExceptionHandler(NullPointerException e) {
        return responseData(CommonConstant.EX_NULL_POINTER_EXCEPTION, e);
    }
 
    /**
     * 类型转换异常
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler(ClassCastException.class)
    public ResponseData classCastExceptionHandler(ClassCastException e) {
        return responseData(CommonConstant.EX_CLASS_CAST_EXCEPTION, e);
    }
 
    /**
     * IO异常
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler(IOException.class)
    public ResponseData iOExceptionHandler(IOException e) {
        return responseData(CommonConstant.EX_IO_EXCEPTION, e);
    }
 
    /**
     * 未知方法异常
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler(NoSuchMethodException.class)
    public ResponseData noSuchMethodExceptionHandler(NoSuchMethodException e) {
        return responseData(CommonConstant.EX_NO_SUCH_METHOD_EXCEPTION, e);
    }
 
    /**
     * 数组越界异常
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler(IndexOutOfBoundsException.class)
    public ResponseData indexOutOfBoundsExceptionHandler(IndexOutOfBoundsException e) {
        return responseData(CommonConstant.EX_INDEX_OUT_OF_BOUNDS_EXCEPTION, e);
    }
 
    /**
     * 请求body缺失异常
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler({HttpMessageNotReadableException.class})
    public ResponseData requestNotReadable(HttpMessageNotReadableException e) {
        return responseData(CommonConstant.EX_HTTP_MESSAGE_NOT_READABLE_EXCEPTION, e);
    }
 
    /**
     * 类型匹配异常
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler({TypeMismatchException.class})
    public ResponseData requestTypeMismatch(TypeMismatchException e) {
        return responseData(CommonConstant.EX_HTTP_MESSAGE_NOT_READABLE_EXCEPTION, e);
    }
 
    /**
     * 方法不支持异常
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler({HttpRequestMethodNotSupportedException.class})
    public ResponseData methodNotSupported(HttpRequestMethodNotSupportedException e) {
        return responseData(CommonConstant.EX_HTTP_REQUEST_METHOD_NOT_SUPPORTED_EXCEPTION, e);
    }
 
    /**
     * 请求头不支持异常
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler({HttpMediaTypeNotSupportedException.class})
    public ResponseData mediaTypeNotAcceptable(HttpMediaTypeNotSupportedException e) {
        return responseData(CommonConstant.EX_HTTP_MEDIA_TYPE_NOT_ACCEPTABLE_EXCEPTION, e);
    }
 
    /**
     * 参数解析异常
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler(JSONException.class)
    public ResponseData runtimeExceptionHandler(JSONException e) {
        return responseData(CommonConstant.PARAMS_PARSE_EXCEPTION, e);
    }
 
    /**
     * 参数解析异常
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler(JsonParseException.class)
    public ResponseData runtimeExceptionHandler(JsonParseException e) {
        return responseData(CommonConstant.PARAMS_PARSE_EXCEPTION, e);
    }
 
    /**
     * 请求参数缺失异常
     *
     * @param e 异常
     * @return
     */
 
    @ExceptionHandler({MissingServletRequestParameterException.class})
    public ResponseData requestMissingServletRequest(MissingServletRequestParameterException e) {
        return responseData(CommonConstant.EX_MISSING_SERVLET_REQUEST_PARAMETER_EXCEPTION, e);
    }
 
    /**
     * 参数不能为空
     *
     * @param e 异常
     * @return
     */
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseData exceptionHandler(MethodArgumentNotValidException e) {
        return responseData(CommonConstant.PARAMS_IS_NULL, e);
    }
}

常量类 CommonConstant

package com.study.auth.constant;
 
/**
 * @Package: com.study.auth.constant
 * @Description: <公共常量类>
 * @Author: milla
 * @CreateDate: 2020/09/04 15:37
 * @UpdateUser: milla
 * @UpdateDate: 2020/09/04 15:37
 * @UpdateRemark: <>
 * @Version: 1.0
 */
public final class CommonConstant {
    /**
     * 当前用户名称
     */
    public static final String C_CURRENT_ACCOUNT = "current_account";
 
    /**
     * 用户未登录
     */
    public static final String EX_NO_TOKEN_EXCEPTION = "1001";
 
    //--------------------------------非业务返回码---------------------------------------
    /**
     * 运行时异常
     */
    public static final String EX_RUN_TIME_EXCEPTION = "1100";
    /**
     * 空指针异常
     */
    public static final String EX_NULL_POINTER_EXCEPTION = "1101";
    /**
     * 数据转换异常
     */
    public static final String EX_CLASS_CAST_EXCEPTION = "1102";
    /**
     * IO异常
     */
    public static final String EX_IO_EXCEPTION = "1103";
    /**
     * 找不到该方法异常
     */
    public static final String EX_NO_SUCH_METHOD_EXCEPTION = "1104";
    /**
     * 数组越界异常
     */
    public static final String EX_INDEX_OUT_OF_BOUNDS_EXCEPTION = "1105";
    /**
     * 请求体缺失异常
     */
    public static final String EX_HTTP_MESSAGE_NOT_READABLE_EXCEPTION = "1106";
    /**
     * TYPE匹配异常
     */
    public static final String EX_TYPE_MISMATCH_EXCEPTION = "1107";
    /**
     * 请求参数丢失
     */
    public static final String EX_MISSING_SERVLET_REQUEST_PARAMETER_EXCEPTION = "1108";
    /**
     * 请求方法类型不支持异常
     */
    public static final String EX_HTTP_REQUEST_METHOD_NOT_SUPPORTED_EXCEPTION = "1109";
    /**
     * MEDIA 类型不支持异常
     */
    public static final String EX_HTTP_MEDIA_TYPE_NOT_ACCEPTABLE_EXCEPTION = "1110";
    /**
     * 参数解析异常
     */
    public static final String PARAMS_PARSE_EXCEPTION = "1111";
    /**
     * 参数不能为空
     */
    public static final String PARAMS_IS_NULL = "1112";
    //-----------------------------------------------------------------------------------
}

自定义异常类 CustomMessageException

package com.study.auth.exception;
 
/**
 * @Package: com.study.auth.exception
 * @Description: <自定义异常类>
 * @Author: MILLA
 * @CreateDate: 2019/8/15 18:39
 * @UpdateUser: MILLA
 * @UpdateDate: 2019/8/15 18:39
 * @UpdateRemark: <>
 * @Version: 1.0
 */
public class CustomMessageException extends RuntimeException {
 
    public CustomMessageException() {
        super();
    }
 
    public CustomMessageException(String message) {
        super(message);
    }
 
    public CustomMessageException(String message, Throwable cause) {
        super(message, cause);
    }
 
    public CustomMessageException(Throwable cause) {
        super(cause);
    }
 
    protected CustomMessageException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
        super(message, cause, enableSuppression, writableStackTrace);
    }
}

所需依赖
因为使用了阿里的fastJson工具类还需要进入该类的依赖

<dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>fastjson</artifactId>
      <version>1.2.58</version>
  </dependency>

至此，可以愉快的使用该返回值的增强类了，在为服务中，还以将该代码重构到comm中，供多个服务共同使用，避免重复早轮子

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