spring boot 错误处理机制

参考：https://docs.spring.io/spring-boot/docs/1.5.4.RELEASE/reference/htmlsingle/#boot-features-error-handling

spring boot 提供了默认的/error路径，并展示一个全局的错误页面。 以下几种方式用来自定义错误处理：

（1）实现 ErrorController 接口或者继承BasicErrorController类

BasicErrorController类如下：

package org.springframework.boot.autoconfigure.web.servlet.error;

import java.util.Collections;
import java.util.List;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.boot.autoconfigure.web.ErrorProperties;
import org.springframework.boot.autoconfigure.web.ErrorProperties.IncludeStacktrace;
import org.springframework.boot.web.servlet.error.ErrorAttributes;
import org.springframework.boot.web.servlet.server.AbstractServletWebServerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.util.Assert;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

/**
 * Basic global error {@link Controller}, rendering {@link ErrorAttributes}. More specific
 * errors can be handled either using Spring MVC abstractions (e.g.
 * {@code @ExceptionHandler}) or by adding servlet
 * {@link AbstractServletWebServerFactory#setErrorPages server error pages}.
 *
 * @author Dave Syer
 * @author Phillip Webb
 * @author Michael Stummvoll
 * @author Stephane Nicoll
 * @see ErrorAttributes
 * @see ErrorProperties
 */
@Controller
@RequestMapping("${server.error.path:${error.path:/error}}")
public class BasicErrorController extends AbstractErrorController {

    private final ErrorProperties errorProperties;

    /**
     * Create a new {@link BasicErrorController} instance.
     * @param errorAttributes the error attributes
     * @param errorProperties configuration properties
     */
    public BasicErrorController(ErrorAttributes errorAttributes,
            ErrorProperties errorProperties) {
        this(errorAttributes, errorProperties, Collections.emptyList());
    }

    /**
     * Create a new {@link BasicErrorController} instance.
     * @param errorAttributes the error attributes
     * @param errorProperties configuration properties
     * @param errorViewResolvers error view resolvers
     */
    public BasicErrorController(ErrorAttributes errorAttributes,
            ErrorProperties errorProperties, List<ErrorViewResolver> errorViewResolvers) {
        super(errorAttributes, errorViewResolvers);
        Assert.notNull(errorProperties, "ErrorProperties must not be null");
        this.errorProperties = errorProperties;
    }

    @Override
    public String getErrorPath() {
        return this.errorProperties.getPath();
    }
　　
　　
　　//当为网页请求时返回error页面
    @RequestMapping(produces = "text/html")
    public ModelAndView errorHtml(HttpServletRequest request,
            HttpServletResponse response) {
        HttpStatus status = getStatus(request);
        Map<String, Object> model = Collections.unmodifiableMap(getErrorAttributes(
                request, isIncludeStackTrace(request, MediaType.TEXT_HTML)));
        response.setStatus(status.value());
        ModelAndView modelAndView = resolveErrorView(request, response, status, model);
        return (modelAndView != null) ? modelAndView : new ModelAndView("error", model);
    }
　　
　　//当为其他请求时，返回ResponseEntity
    @RequestMapping
    @ResponseBody
    public ResponseEntity<Map<String, Object>> error(HttpServletRequest request) {
        Map<String, Object> body = getErrorAttributes(request,
                isIncludeStackTrace(request, MediaType.ALL));
        HttpStatus status = getStatus(request);
        return new ResponseEntity<>(body, status);
    }

    /**
     * Determine if the stacktrace attribute should be included.
     * @param request the source request
     * @param produces the media type produced (or {@code MediaType.ALL})
     * @return if the stacktrace attribute should be included
     */
    protected boolean isIncludeStackTrace(HttpServletRequest request,
            MediaType produces) {
        IncludeStacktrace include = getErrorProperties().getIncludeStacktrace();
        if (include == IncludeStacktrace.ALWAYS) {
            return true;
        }
        if (include == IncludeStacktrace.ON_TRACE_PARAM) {
            return getTraceParameter(request);
        }
        return false;
    }

    /**
     * Provide access to the error properties.
     * @return the error properties
     */
    protected ErrorProperties getErrorProperties() {
        return this.errorProperties;
    }

}

通过errorHtml和error方法来处理异常。这两个方法中都有一个关键的方法getErrorAttributes，这个方法是其父类AbstractErrorController的方法，代码如下：

public abstract class AbstractErrorController implements ErrorController {

    private final ErrorAttributes errorAttributes;
    
    protected Map<String, Object> getErrorAttributes(HttpServletRequest request,boolean includeStackTrace) {
    　　WebRequest webRequest = new ServletWebRequest(request);
    　　return this.errorAttributes.getErrorAttributes(webRequest, includeStackTrace);
    }
　　...
}

可以看出，上述方法调用的其实是ErrorAttributes的getErrorAttributes方法，所以可以直接实现ErrorAttributes 接口，即第二种方法。

（2）实现ErrorAttributes 接口或者继承DefaultErrorAttributes类

继承DefaultErrorAttributes类并重写的getErrorAttributes方法

（3）使用@ControllerAdvice注解

例如：

@ControllerAdvice(basePackageClasses = FooController.class)
public class FooControllerAdvice extends ResponseEntityExceptionHandler {

    @ExceptionHandler(YourException.class)
    @ResponseBody
    ResponseEntity<?> handleControllerException(HttpServletRequest request, Throwable ex) {
        HttpStatus status = getStatus(request);
        return new ResponseEntity<>(new CustomErrorType(status.value(), ex.getMessage()), status);
    }

    private HttpStatus getStatus(HttpServletRequest request) {
        Integer statusCode = (Integer) reques通过e("javax.servlet.error.status_code");
        if (statusCode == null) {
            return HttpStatus.INTERNAL_SERVER_ERROR;
        }
        return HttpStatus.valueOf(statusCode);
    }

}

如果和FooControllerAdvice 在同一个包下的controller类抛出YourException异常，那么就会返回CustomErrorType类型的json。