Spring進階之@ControllerAdvice與統一異常處理

@ControllerAdvice

Spring源碼中有關@ControllerAdvice的註解以下：

Specialization of {@link Component @Component} for classes that declare {@link ExceptionHandler @ExceptionHandler}, {@link InitBinder @InitBinder}, or {@link ModelAttribute @ModelAttribute} methods to be shared across multiple {@code @Controller} classes.

理解：

@ControllerAdvice是一個特殊的@Component，用於標識一個類，這個類中被如下三種註解標識的方法：@ExceptionHandler，@InitBinder，@ModelAttribute，將做用於全部的@Controller類的接口上。

那麼，這個三個註解分別是什麼意思，起到什麼做用呢？

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@InitBinder

Annotation that identifies methods which initialize the {@link org.springframework.web.bind.WebDataBinder} which will be used for populating command and form object arguments of annotated handler methods. Such init-binder methods support all arguments that {@link RequestMapping} supports, except for command/form objects and corresponding validation result objects. Init-binder methods must not have a return value; they are usually declared as {@code void}.

做用：註冊屬性編輯器，對HTTP請求參數進行處理，再綁定到對應的接口，好比格式化的時間轉換等。應用於單個@Controller類的方法上時，僅對該類裏的接口有效。與@ControllerAdvice組合使用可全局生效。

示例：

@ControllerAdvice
public class ActionAdvice {
    
    @InitBinder
    public void handleException(WebDataBinder binder) {
        binder.addCustomFormatter(new DateFormatter("yyyy-MM-dd HH:mm:ss"));
    }
}
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@ExceptionHandler

做用：統一異常處理，也能夠指定要處理的異常類型

示例：

@ControllerAdvice
public class ActionAdvice {
    
    @ExceptionHandler(Exception.class)
    @ResponseBody
    @ResponseStatus(HttpStatus.OK)
    public Map handleException(Exception ex) {
        Map<String, Object> map = new HashMap<>();
        map.put("code", 400);
        map.put("msg", ex.toString());
        return map;
    }
}
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@ModelAttribute

做用：綁定數據

示例：

@ControllerAdvice
public class ActionAdvice {
    
    @ModelAttribute
    public void handleException(Model model) {
        model.addAttribute("user", "zfh");
    }
}
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在接口中獲取前面綁定的參數：

@RestController
public class BasicController {
    
    @GetMapping(value = "index")
    public Map index(@ModelAttribute("user") String user) {
        //...
    }
}
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完整示例代碼：

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.format.datetime.DateFormatter;
import org.springframework.http.HttpStatus;
import org.springframework.ui.Model;
import org.springframework.validation.Validator;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.*;

import java.util.HashMap;
import java.util.Map;

/** * 統一異常處理 * @author zfh * @version 1.0 * @since 2019/1/4 15:23 */
@ControllerAdvice
public class ControllerExceptionHandler {

    private Logger logger = LoggerFactory.getLogger(ControllerExceptionHandler.class);

    @InitBinder
    public void initMyBinder(WebDataBinder binder) {
        // 添加對日期的統一處理
        //binder.addCustomFormatter(new DateFormatter("yyyy-MM-dd"));
        binder.addCustomFormatter(new DateFormatter("yyyy-MM-dd HH:mm:ss"));

        // 添加表單驗證
        //binder.addValidators();
    }

    @ModelAttribute
    public void addMyAttribute(Model model) {
        model.addAttribute("user", "zfh"); // 在@RequestMapping的接口中使用@ModelAttribute("name") Object name獲取
    }

    @ExceptionHandler(value = Exception.class)
    @ResponseStatus(HttpStatus.OK)
    @ResponseBody // 若是使用了@RestControllerAdvice，這裏就不須要@ResponseBody了
    public Map handler(Exception ex) {
        logger.error("統一異常處理", ex);
        Map<String, Object> map = new HashMap<>();
        map.put("code", 400);
        map.put("msg", ex);
        return map;
    }
}
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測試接口：

@RestController
public class TestAction {

    @GetMapping(value = "testAdvice")
    public JsonResult testAdvice(@ModelAttribute("user") String user, Date date) throws Exception {
        System.out.println("user: " + user);
        System.out.println("date: " + date);
        throw new Exception("直接拋出異常");
    }
}
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高階應用--格式化時間轉Date

使用@ControllerAdvice + @InitBinder，可將http請求參數中的時間自動轉換成Date類型。

@InitBinder
    public void initBinder(WebDataBinder binder) {
        GenericConversionService genericConversionService = (GenericConversionService) binder.getConversionService();
        if (genericConversionService != null) {
            genericConversionService.addConverter(new DateConverter());
        }
    }

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自定義的時間類型轉換器：

import org.springframework.core.convert.converter.Converter;
import org.springframework.util.StringUtils;

import java.text.SimpleDateFormat;
import java.util.Date;

/** * 日期轉換類 * 將標準日期、標準日期時間、時間戳轉換成Date類型 */
public class DateConverter implements Converter<String, Date> {
    private static final String dateFormat = "yyyy-MM-dd HH:mm:ss";
    private static final String shortDateFormat = "yyyy-MM-dd";
    private static final String timeStampFormat = "^\\d+$";

    @Override
    public Date convert(String value) {

        if(StringUtils.isEmpty(value)) {
            return null;
        }

        value = value.trim();

        try {
            if (value.contains("-")) {
                SimpleDateFormat formatter;
                if (value.contains(":")) {
                    formatter = new SimpleDateFormat(dateFormat);
                } else {
                    formatter = new SimpleDateFormat(shortDateFormat);
                }
                return formatter.parse(value);
            } else if (value.matches(timeStampFormat)) {
                Long lDate = new Long(value);
                return new Date(lDate);
            }
        } catch (Exception e) {
            throw new RuntimeException(String.format("parser %s to Date fail", value));
        }
        throw new RuntimeException(String.format("parser %s to Date fail", value));
    }
}
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擴展：

@RestControllerAdvice = @ControllerAdvice + @ResponseBody

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參考：

1. Spring Boot 系列（八）@ControllerAdvice 攔截異常並統一處理
2. SpringMVC重要註解（二）@ControllerAdvice
3. 精通Spring Boot —— 第十五篇：使用@ControllerAdvice處理異常
4. @InitBinder
5. SpringMVC中利用@InitBinder來對頁面數據進行解析綁定