Spring Mvc全局异常捕获

我们在开发过程中，可能希望能够统一地捕获和处理异常，免得异常处理分布在代码各处

我们可以使用spring mvc提供的全局异常捕获来实现这样的功能

首先我们新建一个专门复杂异常处理的工程

com.lzw.exception.exception包里是我们自定义的Exception

package com.lzw.exceptions.exception;

public class BookingExpiredException extends Exception {

	/**
	 * 
	 */
	private static final long serialVersionUID = 573537091646842099L;

}

com.lzw.exceptions.handler包里面是我们对异常的处理

package com.lzw.exceptions.handler;

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.ResponseStatus;

import com.lzw.exceptions.exception.BookingExpiredException;
import com.lzw.exceptions.exception.BookingNoSeatsException;

public class BookingExceptionHandler {
	
	@ExceptionHandler(value = BookingNoSeatsException.class)
	@ResponseStatus(value = HttpStatus.INTERNAL_SERVER_ERROR, reason = "no seats")
	@ResponseBody
	public void handleNoSeatsException(BookingNoSeatsException exception) {
		System.out.println("BookingNoSeatsException!");
	}
	
	@ExceptionHandler(value = BookingExpiredException.class)
	@ResponseStatus(value = HttpStatus.INTERNAL_SERVER_ERROR, reason = "booking expired")
	@ResponseBody
	public void handleExpiredException(BookingExpiredException exception) {
		System.out.println("BookingExpiredException!");
	}
}

com.lzw.exceptions.resolver包里面的类负责对异常进行捕获

package com.lzw.exceptions.resolver;

import java.lang.reflect.Method;

import org.springframework.core.Ordered;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.method.annotation.ExceptionHandlerMethodResolver;
import org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver;
import org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod;

public class BookingExceptionHandlerResolver extends
		ExceptionHandlerExceptionResolver {

	private Object handler;
	private ExceptionHandlerMethodResolver methodResolver;

	public BookingExceptionHandlerResolver() {
		setOrder(Ordered.HIGHEST_PRECEDENCE);
	}

	public void setExceptionHandler(final Object handler) {
		this.handler = handler;
		this.methodResolver = new ExceptionHandlerMethodResolver(
				handler.getClass());
	}

	protected ServletInvocableHandlerMethod getExceptionHandlerMethod(
			final HandlerMethod handlerMethod, final Exception exception) {
		ServletInvocableHandlerMethod result = super.getExceptionHandlerMethod(
				handlerMethod, exception);
		if (result != null) {
			return result;
		}
		Method method = this.methodResolver.resolveMethod(exception);
		return (method != null) ? new ServletInvocableHandlerMethod(
				this.handler, method) : null;
	};
}

ExceptionHandlerExceptionResolver是spring mvc默认的异常处理器，我们可以通过继承它来实现自己的处理逻辑

例如上面，我们继承并实现了自己的BookingExceptionHandlerResolver，注入自己的异常处理器（BookingExceptionHandler），重写了getExceptionHandlerMethod,使得异常发生时能从BookingExceptionHandler里面取得处理该异常的处理方法

当业务代码抛出异常的时候，如果所在的Controller没有对异常进行处理，那么异常就会抛出到Spring Mvc，Spring Mvc会在各个ExceptionHandlerExceptionResolver类（或子类）里面查找能够处理该异常的handler，然后在handler里面找到处理那种异常的方法并执行

编写好以上类后，我们通过把ExceptionHandlerExceptionResolver给声明为bean

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"
	xmlns:p="http://www.springframework.org/schema/p" xmlns:context="http://www.springframework.org/schema/context"
	xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context-3.2.xsd
            http://www.springframework.org/schema/aop
            http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
            http://www.springframework.org/schema/tx
            http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
            http://www.springframework.org/schema/mvc
            http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context-3.2.xsd">

	<bean class="com.lzw.exceptions.resolver.BookingExceptionHandlerResolver">
		<property name="exceptionHandler">
			<bean class="com.lzw.exceptions.handler.BookingExceptionHandler" />
		</property>
		<property name="messageConverters">
			<list>
				<bean
					class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter" />
			</list>
		</property>
	</bean>

	<bean class="com.lzw.exceptions.resolver.PayExceptionHandlerResolver">
		<property name="exceptionHandler">
			<bean class="com.lzw.exceptions.handler.PayExceptionHandler" />
		</property>
		<property name="messageConverters">
			<list>
				<bean
					class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter" />
			</list>
		</property>
	</bean>

</beans>

这样最后把整个工程打成jar包，给其他工程使用

下面新建一个代表业务的工程

把之前的Exception工程通过maven给依赖进来

然后在Spring Mvc配置文件中引入Exception工程的配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"
	xmlns:p="http://www.springframework.org/schema/p" xmlns:context="http://www.springframework.org/schema/context"
	xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context-3.2.xsd
            http://www.springframework.org/schema/aop
            http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
            http://www.springframework.org/schema/tx
            http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
            http://www.springframework.org/schema/mvc
            http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context-3.2.xsd">

	<context:component-scan base-package="com.lzw.business" />
	<mvc:annotation-driven />

	<import resource="classpath:com/lzw/exceptions/exceptions.xml"/>
	
</beans>

最后看看Mvc的Controller

package com.lzw.business;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import com.lzw.exceptions.exception.BookingExpiredException;
import com.lzw.exceptions.exception.BookingNoSeatsException;
import com.lzw.exceptions.exception.PayNoMoneyException;
import com.lzw.exceptions.exception.PayTimeoutException;


@Controller
public class Test {
	
	@RequestMapping(value = "/testbooknoseats")
	public void TestBookingNoSeats() throws BookingNoSeatsException {
		throw new BookingNoSeatsException();
	}
	
	@RequestMapping(value = "/testbookexpired")
	public void TestBookingExpired() throws BookingExpiredException {
		throw new BookingExpiredException();
	}
	
	@RequestMapping(value = "/paynomoney")
	public void TestPayNoMoney() throws PayNoMoneyException {
		throw new PayNoMoneyException();
	}
	
	@RequestMapping(value = "/paytimeout")
	public void TestPayTimeout() throws PayTimeoutException {
		throw new PayTimeoutException();
	}
}

测试一下