1：启动SpringMVC的注解功能，完成请求和注解POJO的映射
（1）Spring3.1前的注解<bean
class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping "/>
<bean
class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"> </bean>
（2）Spring3.1开始的注解
<bean
class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping"/>
<bean
class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter"/>
<mvc:annotation-driven/>相当于注册了RequestMappingHandlerMapping和RequestMappingHandlerAdapter两个bean，配置一些messageconverter。即解决了@Controller注解的使用前提配置。
2：MappingJacksonHttpMessageConverter——JSON转换器，bean可以自动转换json
pom.xml需要配置<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.9.4</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>2.9.4</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.4</version>
</dependency>
<bean id="mappingJacksonHttpMessageConverter"
class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
<property name="supportedMediaTypes">
<list>
<value>text/html;charset=UTF-8</value>
</list>
</property>
</bean>
这里jackson-core版本是2以上的所以
class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter”
若果版本是1以下
class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"
3:数据库连不上org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection
检查：jdbc.properties文件jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/weiyuan?characterEncoding=utf8
jdbc.username=root
jdbc.password=root
#定义初始连接数
jdbc.initialSize=0
#定义最大连接数
jdbc.maxActive=20
#定义最大空闲
jdbc.maxIdle=20
#定义最小空闲
jdbc.minIdle=1
#定义最长等待时间
jdbc.maxWait=60000
注：每行后面不要留空格或空字符否则会报错
spring-mybatis.xml文件
<!--引入配置文件 -->
<bean id="propertyConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location" value="classpath:jdbc.properties" />
</bean>
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
destroy-method="close">
<property name="driverClassName" value="${jdbc.driver}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
<!--初始化连接大小 -->
<property name="initialSize" value="${jdbc.initialSize}"></property>
<!--连接池最大数量 -->
<property name="maxActive" value="${jdbc.maxActive}"></property>
<!--连接池最大空闲 -->
<property name="maxIdle" value="${jdbc.maxIdle}"></property>
<!--连接池最小空闲 -->
<property name="minIdle" value="${jdbc.minIdle}"></property>
<!--获取连接最大等待时间 -->
<property name="maxWait" value="${jdbc.maxWait}"></property>
</bean>
4:@Autowired注解：Request processing failed; nested exception is java.lang.NullPointerException
缺少注解；我出现问题是缺少@Autowired注解@Service("userService")
public class TcUserServiceImpl implements com.qn.service.TcUserService {
@Autowired
private TcUserMapper tcUserMapper;
public int insertTcUser(TcUser record) {
int retResult = tcUserMapper.insertSelective(record);
return retResult;
}
}