一、Maven多模块项目的创建
我们需要建立一个多模块的maven项目，其目录结构为
其中student-api用于暴露接口；student-service用语处理业务逻辑及调用数据访问对象，返回相应数据；student-web主要用于提供dubbo服务，及其他db、spring、springMVC、mybatis等配置。这样设计能够将业务逻辑与数据访问隔离开，同时贴合了spring目标之一，就是允许我们在开发应用的程序时，能够遵循面向对象（OO）原则中的“针对接口编程”，很大程度上达到松耦合。这里将接口API隔离出来作为dubbo生产者的服务接口，供消费应用调用（在后续详细讲解）。
1.新建Maven项目
2.选择项目存放路径后，选择创建一个简单的maven项目
3.
3.填写GroupId和ArtifactId,注意选择或者填写版本号
点击完成后，建立好了student-demo项目。之后删除项目src目录，打开pom.xml将<packaging>jar</packaging>修改为<packaging>pom</packaging>，pom表示它是一个被继承的模块。修改后的pom.xml如下
`<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">;
<modelVersion>4.0.0</modelVersion>
<groupId>com.student.demo</groupId>
<artifactId>student-demo</artifactId>
<version>1.0.0-SNAPSHOT</version>
<packaging>pom</packaging>
<name>student-demo</name>
<url>http://maven.apache.org</url>;
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
student-service
student-api
student-web
junit
junit
3.8.1
test
`
在建成的项目student-demo上右键选择Maven Module后创建子项目student-api。
填写子模块名字：
项目类型选择：
点击完成，建立好第一个模块后，同样的过程建立好student-service模块和student-web模块，需要注意的是student-web选择的maven类型是：
修改子模块项目目录中的pom.xml文件，把XXX和1.0.0-SNAPSHOT去掉，加上jar，因为groupId和version会继承student-demo中的groupId和version，packaging设置打包方式为jar。例如修改后的student-service模块的pom.xml如下：
```
4.0.0
com.student.demo
student-demo
1.0.0-SNAPSHOT
student-service
jar
```
至此，maven多模块项目已经创建完成，现在我们需要在student-demo项目的pom中增加标签定义可被子项目继承的第三方依赖包，打包配置，资源插件等，同时注意统一定义依赖的版本，避免冲突。这里还利用Maven配置了profiles，可根据情况增加不同的运行环境，并方便快捷地切换项目运行环境，目前我们只设置了dev开发环境。
```
4.0.0
com.student.demo
student-demo
1.0.0-SNAPSHOT
pom
UTF-8
1.16.10
1.0.1
5.1.21
4.2.5.RELEASE
3.3.0
1.3.0
4.1.6
1.5.4
1.8.0
3.1.0
1.4.6
3.20.0-GA
2.7
1.4.2
2.2.4
15.0
1.7.21
1.1.7
1.2.12
1.7.5
0.1.2
2.5.3
3.4.8
0.8
3.1
1.9.12
1.2.3
2.3.22
1.9.2
4.11
1.10.19
2.9.3
4.1
4.5.2
1.2.11
2.7
2.5.1
3.0.0
1.14.8.0
1.8
UTF-8
${project.artifactId}
src/profiles
2.6.0
student-service
student-api
student-web
org.hibernate
hibernate-validator
5.2.4.Final
org.springframework
spring-core
${dep.ver.springframework}
commons-logging
commons-logging
org.springframework
spring-context
${dep.ver.springframework}
org.springframework
spring-context-support
${dep.ver.springframework}
org.springframework
spring-web
${dep.ver.springframework}
org.springframework
spring-webmvc
${dep.ver.springframework}
org.springframework
spring-jdbc
${dep.ver.springframework}
org.springframework
spring-tx
${dep.ver.springframework}
org.springframework
spring-aspects
${dep.ver.springframework}
com.alibaba
druid
${dep.ver.druid}
mysql
mysql-connector-java
${dep.ver.mysql}
org.mybatis
mybatis
${dep.ver.mybatis}
org.mybatis
mybatis-spring
${dep.ver.mybatis-spring}
com.github.pagehelper
pagehelper
${dep.ver.pagehelper}
org.apache.commons
commons-lang3
${dep.ver.commons-lang3}
commons-beanutils
commons-beanutils
${dep.ver.commons-beanutils}
commons-logging
commons-logging
org.slf4j
slf4j-api
${dep.ver.slf4j}
org.slf4j
log4j-over-slf4j
${dep.ver.slf4j}
org.slf4j
jcl-over-slf4j
${dep.ver.slf4j}
ch.qos.logback
logback-classic
${dep.ver.logback}
com.alibaba
dubbo
${dep.ver.dubbo}
spring
org.springframework
netty
org.jboss.netty
org.apache.zookeeper
zookeeper
${dep.ver.zookeeper}
log4j
log4j
com.101tec
zkclient
${dep.ver.zkclient}
log4j
log4j
org.codehaus.jackson
jackson-core-asl
${dep.ver.jackson}
org.codehaus.jackson
jackson-mapper-asl
${dep.ver.jackson}
aspectj
aspectjrt
${dep.ver.aspectjrt}
org.aspectj
aspectjweaver
${dep.ver.aspectjweaver}
javax.servlet
javax.servlet-api
${dep.ver.servlet}
provided
org.javassist
javassist
${dep.ver.javassist}
junit
junit
${dep.ver.junit}
test
org.springframework
spring-test
${dep.ver.springframework}
test
org.mockito
mockito-core
${dep.ver.mockito}
test
com.google.code.gson
gson
${dep.ver.gson}
com.google.guava
guava
${dep.ver.guava}
org.projectlombok
lombok
${dep.ver.lombok}
org.apache.commons
commons-collections4
${dep.ver.commons-collections4}
org.apache.httpcomponents
httpclient
${dep.ver.httpclient}
commons-logging
commons-logging
local
${profiles.dir}/local
dev
${profiles.dir}/dev
${center.project.name}
org.apache.maven.plugins
maven-resources-plugin
${plg.ver.maven-resources-plugin}
${encoding}
org.apache.maven.plugins
maven-compiler-plugin
${plg.ver.maven-compiler-plugin}
${jdk.ver}
${jdk.ver}
${encoding}
maven-source-plugin
${plg.ver.maven-source-plugin}
true
compile
jar
src/main/resources
true
```
在student-api中继承父pom的依赖，并且直接引入。
```
4.0.0
com.student.demo
student-demo
1.0.0-SNAPSHOT
student-api
com.alibaba
fastjson
${dep.ver.fastjson}
org.springframework
spring-context
org.springframework
spring-web
org.apache.httpcomponents
httpclient
com.google.code.gson
gson
com.google.guava
guava
```
在student-service中添加继承依赖，添加对student-api的依赖。
```
4.0.0
com.student.demo
student-demo
1.0.0-SNAPSHOT
student-service
com.student.demo
student-api
1.0.0-SNAPSHOT
com.alibaba
fastjson
${dep.ver.fastjson}
com.aliyun.oss
aliyun-sdk-oss
2.0.7
commons-logging
commons-logging
com.alibaba
druid
mysql
mysql-connector-java
org.mybatis
mybatis
org.mybatis
mybatis-spring
com.github.pagehelper
pagehelper
org.springframework
spring-core
org.springframework
spring-context
org.springframework
spring-webmvc
org.springframework
spring-jdbc
org.springframework
spring-context-support
org.springframework
spring-tx
org.springframework
spring-aspects
com.fasterxml.jackson.core
jackson-core
${jackson.version}
com.fasterxml.jackson.core
jackson-databind
${jackson.version}
com.fasterxml.jackson.core
jackson-annotations
${jackson.version}
org.slf4j
slf4j-api
ch.qos.logback
logback-classic
org.slf4j
log4j-over-slf4j
org.slf4j
jcl-over-slf4j
com.google.guava
guava
org.apache.commons
commons-lang3
commons-beanutils
commons-beanutils
javax.servlet
javax.servlet-api
org.javassist
javassist
aspectj
aspectjrt
org.aspectj
aspectjweaver
com.alibaba
dubbo
spring
org.springframework
netty
org.jboss.netty
org.apache.zookeeper
zookeeper
org.slf4j
slf4j-log4j12
com.101tec
zkclient
org.slf4j
slf4j-log4j12
org.apache.httpcomponents
httpclient
cglib
cglib
3.1
```
在student-web中继承依赖，添加对student-api，student-service的依赖。注意子项目依赖版本都为1.0.0-SNAPSHOT
```
4.0.0
com.student.demo
student-demo
1.0.0-SNAPSHOT
student-web
war
junit
junit
com.student.demo
student-api
1.0.0-SNAPSHOT
com.student.demo
student-service
1.0.0-SNAPSHOT
student-web
```
```
二、Maven与SpringMVC的整合
1.第一部分已经在项目pom文件中配置了spring的相关依赖
2.在student-web项目根路径上添加profiles源目录及配置文件
注意是建立源文件不是普通文件夹。
然后在此源文件夹下建立普通文件夹props，用于存放配置文件。在props下新建db-config.properties资源文件，用于配置mysql，其配置内容为：
```
1 database.database=mysql
2 database.driverClassName=com.mysql.jdbc.Driver
3 database.url=jdbc:mysql://172.0.0.1:3306/student_data?characterEncoding=utf8
4 database.user=root
5 database.password=root
6 database.show_sql=true
```
在mysql数据库中建立一张简单的student数据表，其结构为：
3.在student-web的src/main/resources目录中新建spring文件夹，新建spring-base.xml和spring-dispatcher.xml。其中值得说明一下的是，spring监听器ContextLoaderListener和控制器DispatcherServlet会加载应用上下文。其中上下文参数contextConfigLocation的value值是根应用上下文路径classpath:spring/spring-base.xml，它会被ContextLoaderListener加载bean定义。spring-base.xml中的内容为：
```
classpath:props/db-config.properties
```
同样DispatcherServlet会从classpath:spring/spring-dispatcher.xml加载它的bean。
```
```
4.在Web.xml中声明DispatcherServlet
SpringMVC所有请求都会通过一个前端控制器DispatcherServlet，通过这个控制器将请求委托给应用程序的其它执行单元来处理，所以需要通过web.xml来注册。打开student-web项目目录下src/main/webapp/WEB-INF/web.xml，修改web.xml
`
student-web
contextConfigLocation
classpath:spring/spring-base.xml
org.springframework.web.context.ContextLoaderListener
characterEncodingFilter
org.springframework.web.filter.CharacterEncodingFilter
encoding
UTF-8
forceEncoding
true
characterEncodingFilter
/*
dispatcher
org.springframework.web.servlet.DispatcherServlet
contextConfigLocation
classpath:spring/spring-dispatcher.xml
dispatcher
/
`
5.spring与Mybatis的整合
在student-web的src/main/resources目录中新建mybatis文件夹，再在此目录新建mybatis.xml和mapper文件夹。在spring文件夹下新建spring-db.xml用于spring加载mybatis配置。spring-db.xml内容如下：
```
```
三、Dubbo的环境配置及与整合
我们已经搭建好student-demo项目来作为provider，为其它服务提供接口，所以我们需要先配置好dubbo提供者，PS：这里不会讲解zookeeper的搭建，请自行百度。其项目结构为：
1.首先在student-web中配置dubbo
由于我们已经在student-demo中添加了dubbo和zookeeper的相关依赖，下一步字啊resources目录中建立dubbo文件夹，再新建dubbo-producer.xml，同时在profiles的dev环境中添加dubbo-producer.properties配置文件，设置zookeeper注册中心暴露服务地址，配置group分组，服务端口，注册中心请求超时时间(毫秒)和版本。其中组别＋接口地址＋版本号唯一的标识了一个接口。文件内容为：
```
1 student-registry-address=172.0.0.1:2181
2 student-group=student-min
3 student-service-port=22026
4 student-timeout=120000
5 student-version=1.0.0
```
这样我们就可以来配置dubbo-producer.xml
```
```
2.写一个简单的服务接口
1）首先在student-service中建立Student实体类
```
package org.student.bean;
public class Student {
private Long id;
private String name;
private Integer age;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
}
```
2）同时在student-api中建立与实体bean对应的DTO类实现Serializable接口，并重写toString方法。一般为了不破坏实体类和数据库表一一对应的接口，我们会新建一个DTO实体类，并且加入一些冗余的字段，作为前后端的传输对象。
`package org.student.api.dto;
import java.io.Serializable;
public class StudentDTO implements Serializable{
private static final long serialVersionUID = 1L;
private Long id;
private String name;
private Integer age;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "id = " + id + ", name = " + name + ",age = " + age;
}
}
`
3）在student-api中建立StudentApi接口，值得注意的是@service注解中的对象
```
package org.student.api;
import java.util.List;
import org.student.api.dto.StudentDTO;
public interface StudentApi {
List listStudents();
}
```
4）在dubbo-producer.xml中注册StudentApi，添加配置：
```
```
5）从service业务逻辑层子模块开始编写接口实现，新建在student-service中新建StudentBiz实现StudentApi接口
```
package org.student.service.biz;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.student.api.StudentApi;
import org.student.api.dto.StudentDTO;
import org.student.bean.Student;
import org.student.service.StudentService;
import com.google.common.collect.Lists;
@Service("studentApi")
public class StudentBiz implements StudentApi{
private Logger logger = LoggerFactory.getLogger(StudentBiz.class);
@Autowired
private StudentService studentService;
@Override
public List listStudents() {
List listStudent = studentService.listStudent();
List listStudentDTO = Lists.newArrayList();
for(Student student: listStudent){
StudentDTO studentDTO = new StudentDTO();
studentDTO.setId(student.getId());
studentDTO.setAge(student.getAge());
studentDTO.setName(student.getName());
listStudentDTO.add(studentDTO);
}
return listStudentDTO;
}
}
```
6）在student-service中创建service层接口StudentService
```
package org.student.service;
import java.util.List;
import org.springframework.stereotype.Service;
import org.student.bean.Student;
@Service
public interface StudentService {
List listStudent();
}
```
7）在student-service中实现StudentService接口
```
package org.student.service.impl;
import java.util.List;
import javax.annotation.Resource;
import org.springframework.stereotype.Service;
import org.student.bean.Student;
import org.student.service.StudentService;
import org.student.service.mapper.StudentMapper;
@Service("studentService")
public class StudentServiceImpl implements StudentService{
@Resource
private StudentMapper studentMapper;
@Override
public List listStudent() {
List listStudent = studentMapper.listStudent();
return listStudent;
}
}
```
8）在student-service中创建数据层StudentMapper接口
```
package org.student.service.mapper;
import java.util.List;
import org.student.bean.Student;
public interface StudentMapper {
List listStudent();
}
```
9）在student-web中创建实体映射的XML文件，注意StudentMapper类与sql ID的对应关系
```
a.id,
a.name,
a.age
SELECT
FROM
student a
```
dubbo提供者已创建完成，创建完成子应用结构为
1）dubbo-consumer.properties的service-group应该与提供者一致，否者找不到提供者方的接口。
同时pom.xml中需要增加对的依赖
```
com.student.demo
student-api
1.0.0-SNAPSHOT
```
```
student-registry-address=172.0.0.1:2181
student-service-group=student-min
student-service-version=1.0.0
student-service-timeout=120000
```
2）spring-dubbo-consumer.xml的配置及接口调用方式
`
`
3）调用者的controller层
```
package org.student.controller;
import javax.annotation.Resource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.student.api.StudentApi;
@RestController
@RequestMapping("/student")
public class StudentController {
private static Logger logger = LoggerFactory.getLogger(StudentController.class);
@Resource
private StudentApi studentApi;
@RequestMapping(path = "/listStudent", method = RequestMethod.POST)
public void listStudent(){
logger.info("get students...");
logger.info("the data are " + studentApi.listStudents());
}
}
```
4）服务器同时启动provider和consumer，会看到启动信息
```
查看zookeeper注册中心发现提供者消费者都已成功注册
```
```
```
```
```
5）测试接口
` 由于我并没有写view层来展示数据，现在只能通过控制台的日志信息来简单测试接口。（logback的用法不做解释）利用浏览器post请求访问
http://172.0.0.1:8080/student-test/student/listStudent，控制台输出为
`
```
[http-nio-8080-exec-2] INFO 2016-11-07 18:33:24.450 o.s.c.StudentController[24] - get students...
[DubboServerHandler-172.28.19.7:22026-thread-2] INFO 2016-11-07 18:33:24.729 d.a.o.s.a.StudentApi[58] - [DUBBO] [2016-11-07 18:3:24] 172.28.19.7:56346 -> 172.28.19.7:22026 - student-min/org.student.api.StudentApi:1.0.0 listStudents() , dubbo version: 2.5.3, current host: 127.0.0.1
[http-nio-8080-exec-2] INFO 2016-11-07 18:33:25.026 o.s.c.StudentController[25] - the data are [id = 1, name = 张三,age = 20]
```
四、新手在整合过程易犯的错误。
1.ClassNotFound异常
`严重: Error configuring application listener of class org.springframework.web.context.ContextLoaderListener
java.lang.ClassNotFoundException: org.springframework.web.context.ContextLoaderListener
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1332)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1166)
at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:518)
at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:499)
at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:118)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4764)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5303)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1407)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1397)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
`
eclipse会自动将deployment assembly指定的工程，打成jar包，放入到web-inf/lib目录下，tomcat在发布项目的时候没有同时发布maven依赖所添加的jar包，但是如果在deployment assembly没有配置相应的依赖包，就会抛出异常。解决方法：项目 —> properties
-> Deployment Assembly -> Add -> Java Build Path Entries -> 选择Maven Dependencies -> Finish -> OK 把对应的Maven依赖包也发布到tomcat，调试时会自动把那些jar发布到指定目录下，tomcat也能找到那些jar了。
另外，同样的报错可能由于不同的原因造成，如果没有激活Maven profile也会报这种错误，激活profile的方式有很多，通过命令首先需要在pom.xml中用配置（详细配置请查看上文）再通过命令行：
`mvn install -Pdev #激活dev环境`
也可以通过eclipse的配置：项目－－>properties-->Maven-->填写profile名－－>apply-->finish
2.启动student-web，spring创建bean对象失败
十一月 07, 2016 8:19:24 下午 org.apache.catalina.core.StandardContext listenerStart
严重: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.student.api.StudentApi': Cannot resolve reference to bean 'studentApi' while setting bean property 'ref'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'studentApi' is defined
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:359)
...
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839)
...
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'studentApi' is defined
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinition(DefaultListableBeanFactory.java:698)
at org.springframework.beans.factory.support.AbstractBeanFactory.getMergedLocalBeanDefinition(AbstractBeanFactory.java:1175)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:284)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:351)
...
spring有强大的注解帮助我们简化很大部分代码，并降低的耦合。@Autowired或@Resource在 Bean 类中使用自动注入功能，但是 Bean 还是在 XML 文件中通过
进行定义 —— 也就是说，在 XML 配置文件中定义 Bean，通过@Autowired或@Resource为 Bean 的成员变量、方法入参或构造函数入参提供自动注入的功能。以前通过在spring文件中配置的方式被移除，仅需要添加一行 配置就解决所有问题了——Spring XML 配置文件得到了极致的简化。 的 base-package 属性指定了需要扫描的类包，类包及其递归子包中所有的类都会被处理。解决：在spring-base.xml中添加
``
3.消费者访问dubbo接口被拒绝
`严重: Servlet.service() for servlet [dispatcher] in context with path [] threw exception [Request processing failed; nested exception is com.alibaba.dubbo.rpc.RpcException: Forbid consumer 172.0.0.1 access service org.student.api.StudentApi from registry 172.0.0.1:2181 use dubbo version 2.5.3, Please check registry access list (whitelist/blacklist).] with root cause
com.alibaba.dubbo.rpc.RpcException: Forbid consumer 172.0.0.1 access service org.student.api.StudentApi from registry 172.0.0.1:2181 use dubbo version 2.5.3, Please check registry access list (whitelist/blacklist). at com.alibaba.dubbo.registry.integration.RegistryDirectory.doList(RegistryDirectory.java:579) at com.alibaba.dubbo.rpc.cluster.directory.AbstractDirectory.list(AbstractDirectory.java:73) at com.alibaba.dubbo.rpc.cluster.support.AbstractClusterInvoker.list(AbstractClusterInvoker.java:260) at com.alibaba.dubbo.rpc.cluster.support.AbstractClusterInvoker.invoke(AbstractClusterInvoker.java:219) at com.alibaba.dubbo.rpc.cluster.support.wrapper.MockClusterInvoker.invoke(MockClusterInvoker.java:72) at com.alibaba.dubbo.rpc.proxy.InvokerInvocationHandler.invoke(InvokerInvocationHandler.java:52) at com.alibaba.dubbo.common.bytecode.proxy0.listStudents(proxy0.java) at org.student.controller.StudentController.listStudent(StudentController.java:25) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498)
....
`
如果消费者访问的接口路径不正确，则无法调用接口。出现这种错误是我没有把消费者的组设置成提供者的组，解决方法是group保持一致
4.访问所有接口都报404错误
```
INFO 2016-11-08 12:42:28.507 o.s.w.s.DispatcherServlet[488] - FrameworkServlet 'dispatcher': initialization started
INFO 2016-11-08 12:42:28.518 o.s.w.c.s.XmlWebApplicationContext[578] - Refreshing WebApplicationContext for namespace 'dispatcher-servlet': startup date [Tue Nov 08 12:42:28 CST 2016]; parent: Root WebApplicationContext
INFO 2016-11-08 12:42:28.519 o.s.b.f.x.XmlBeanDefinitionReader[317] - Loading XML bean definitions from class path resource [spring/spring-dispatcher.xml]
INFO 2016-11-08 12:42:28.657 o.s.b.f.s.DefaultListableBeanFactory[839] - Overriding bean definition for bean 'org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping' with a different definition: replacing [Root bean: class [org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping]; scope=; abstract=false; lazyInit=false; autowireMode=0; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null] with [Root bean: class [org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping]; scope=; abstract=false; lazyInit=false; autowireMode=0; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null]
...
INFO 2016-11-08 12:42:29.545 o.s.w.s.m.m.a.RequestMappingHandlerAdapter[532] - Looking for @ControllerAdvice: WebApplicationContext for namespace 'dispatcher-servlet': startup date [Tue Nov 08 12:42:28 CST 2016]; parent: Root WebApplicationContext
INFO 2016-11-08 12:42:29.810 o.s.w.s.v.v.VelocityConfigurer[140] - ClasspathResourceLoader with name 'springMacro' added to configured VelocityEngine
INFO 2016-11-08 12:42:30.193 o.s.w.s.DispatcherServlet[507] - FrameworkServlet 'dispatcher': initialization completed in 1684 ms
WARN 2016-11-08 12:42:30.206 o.s.w.s.PageNotFound[1136] - No mapping found for HTTP request with URI [/student/listStudent] in DispatcherServlet with name 'dispatcher'
```
这个错误我找了很久才发现，并不是简单的访问路径错误。仔细查看日志信息会发现spring加载dispatcher的过程，截取在web.xml中配置
`
contextConfigLocation
classpath:spring/spring-base.xml
...
dispatcher
org.springframework.web.servlet.DispatcherServlet
contextConfigLocation
classpath:spring/spring-dispatcher.xml
dispatcher
/
`
在Tomcat启动时，web.xml中加载顺序是 context-param -> listener -> filter -> servlet，ContextLoaderListener基于Web上下文级别的监听器在启动服务器时就创建ApplicationContext并且将配置的Spring Bean加载到XML中。DispatcherServlet是一个请求分发控制器，所有匹配的URL都会通过该Servlet分发执行，在创建Servlet对象时会初始化Spring
MVC相关配置。spring-dispatcher.xml中定义了控制器映射，使用Controller+RequestMapping注解映射时，相关controller组件扫描要定义在spring-dispatcher.xml中，而非spring-base.xml中。依据这样的分析，我去查看了student-test项目中spring-dispatcher.xml和spring-base.xml的配置，发现spring-base.xml配置了
```
```
而在spring-dispatcher.xml中未配置扫描路径。所以spring无法加载controller中的映射，自然会404了，解决方式则是在spring-dispatcher.xml中加上扫描。
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