Spring+mybatis+maven整合过程加载配置文件jdbc.properties
在整合过程中配置文件中几个引用路径需要主要的地方：
spring-mybatis.xml中
<!-- 引入配置文件 -->
开始的时候，我写的是绝对路径，发现出错了，这样写之后发现，classpath就是src/main/resources
在加载jdbc配置文件的过程中遇到了如下的错误：
java.lang.IllegalStateException: Failed to load ApplicationContext
at org.springframework.test.context.CacheAwareContextLoaderDelegate.loadContext(CacheAwareContextLoaderDelegate.java:99)
at org.springframework.test.context.TestContext.getApplicationContext(TestContext.java:122)
at org.springframework.test.context.web.ServletTestExecutionListener.setUpRequestContextIfNecessary(ServletTestExecutionListener.java:105)
at org.springframework.test.context.web.ServletTestExecutionListener.prepareTestInstance(ServletTestExecutionListener.java:74)
at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:312)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:211)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:288)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:284)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:88)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.mybatis.spring.mapper.MapperScannerConfigurer#0' defined in class path resource [spring-mybatis.xml]: Cannot resolve reference to bean 'sqlSessionFactory' while setting bean property 'sqlSessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sqlSessionFactory' defined in class path resource [spring-mybatis.xml]: Cannot resolve reference to bean 'dataSource' while setting bean property 'dataSource'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [spring-mybatis.xml]: Initialization of bean failed; nested exception is org.springframework.beans.TypeMismatchException: Failed to convert property value of type 'java.lang.String' to required type 'int' for property 'initialSize'; nested exception is java.lang.NumberFormatException: For input string: "${initialSize}"
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:329)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:107)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1387)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1128)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:198)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansOfType(DefaultListableBeanFactory.java:438)
at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:624)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:461)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:120)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:60)
at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.delegateLoading(AbstractDelegatingSmartContextLoader.java:100)
at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.loadContext(AbstractDelegatingSmartContextLoader.java:248)
at org.springframework.test.context.CacheAwareContextLoaderDelegate.loadContextInternal(CacheAwareContextLoaderDelegate.java:64)
at org.springframework.test.context.CacheAwareContextLoaderDelegate.loadContext(CacheAwareContextLoaderDelegate.java:91)
... 25 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sqlSessionFactory' defined in class path resource [spring-mybatis.xml]: Cannot resolve reference to bean 'dataSource' while setting bean property 'dataSource'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [spring-mybatis.xml]: Initialization of bean failed; nested exception is org.springframework.beans.TypeMismatchException: Failed to convert property value of type 'java.lang.String' to required type 'int' for property 'initialSize'; nested exception is java.lang.NumberFormatException: For input string: "${initialSize}"
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:329)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:107)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1387)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1128)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:323)
... 43 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [spring-mybatis.xml]: Initialization of bean failed; nested exception is org.springframework.beans.TypeMismatchException: Failed to convert property value of type 'java.lang.String' to required type 'int' for property 'initialSize'; nested exception is java.lang.NumberFormatException: For input string: "${initialSize}"
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:529)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:323)
... 53 more
Caused by: org.springframework.beans.TypeMismatchException: Failed to convert property value of type 'java.lang.String' to required type 'int' for property 'initialSize'; nested exception is java.lang.NumberFormatException: For input string: "${initialSize}"
at org.springframework.beans.BeanWrapperImpl.convertIfNecessary(BeanWrapperImpl.java:468)
at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:494)
at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:488)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.convertForProperty(AbstractAutowireCapableBeanFactory.java:1433)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1392)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1128)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
... 59 more
Caused by: java.lang.NumberFormatException: For input string: "${initialSize}"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:481)
at java.lang.Integer.valueOf(Integer.java:582)
at org.springframework.util.NumberUtils.parseNumber(NumberUtils.java:155)
at org.springframework.beans.propertyeditors.CustomNumberEditor.setAsText(CustomNumberEditor.java:115)
at org.springframework.beans.TypeConverterDelegate.doConvertTextValue(TypeConverterDelegate.java:452)
at org.springframework.beans.TypeConverterDelegate.doConvertValue(TypeConverterDelegate.java:424)
at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:181)
at org.springframework.beans.BeanWrapperImpl.convertIfNecessary(BeanWrapperImpl.java:448)
... 65 more出错的地方对应下面这段配置文件：
导致的原因总结如下：
在spring里使用org.mybatis.spring.mapper.MapperScannerConfigurer进行自动扫描的时候，设置了sqlSessionFactory的话，可能会导PropertyPlaceholderConfigurer失效，也就是用${jdbc.username}这样之类的表达式，将无法获取到properties文件里的内容导致这一原因是因为，MapperScannerConfigurer实际是在解析加载bean定义阶段的，这个时候要是设置sqlSessionFactory的话，会导致提前初始化一些类，这个时候PropertyPlaceholderConfigurer还没来得及替换定义中的变量，导致把表达式当做字符串复制了。但是如果不设置sqlSessionFactory属性的话，就必须要保证sessionFactory在spring中名称一定要是sqlSessionFactory,否则就无法自动注入。又或者直接定义MapperFactoryBean,再或者放弃自动代理接口方式。
经测试去掉sqlSessionFactory和改成：
在spring里使用org.mybatis.spring.mapper.MapperScannerConfigurer进行自动扫描的时候，设置了sqlSessionFactory的话，可能会导PropertyPlaceholderConfigurer失效，也就是用${jdbc.username}这样之类的表达式，将无法获取到properties文件里的内容导致这一原因是因为，MapperScannerConfigurer实际是在解析加载bean定义阶段的，这个时候要是设置sqlSessionFactory的话，会导致提前初始化一些类，这个时候PropertyPlaceholderConfigurer还没来得及替换定义中的变量，导致把表达式当做字符串复制了。但是如果不设置sqlSessionFactory属性的话，就必须要保证sessionFactory在spring中名称一定要是sqlSessionFactory,否则就无法自动注入。又或者直接定义MapperFactoryBean,再或者放弃自动代理接口方式。
经测试去掉sqlSessionFactory和改成：
改用sqlSessionFactoryBeanName注入就没有问题（不要使用sqlSessionFactory属性注入，使用sqlSessionFactoryBeanName注入），因为这时不会立即初始化sqlSessionFactory，传入的只是名字,非bean，所以不会引发提前初始化问题。
spring 的properties解析
一般使用PropertyPlaceholderConfigurer来替换占位符，例如：
classpath:com/foo/strategy.properties
custom.strategy.class=com.foo.DefaultStrategy
其本质是注册了一个PropertyPlaceholderConfigurer（3.1之前）或者是PropertySourcesPlaceholderConfigurer（3.1之后）
注意：
PropertyPlaceholderConfigurer内置的功能非常丰富，如果它未找到${xxx}中定义的xxx键，它还会去JVM系统属性（System.getProperty()）和环境变量（System.getenv()）中寻找。通过启用systemPropertiesMode和searchSystemEnvironment属性，开发者能够控制这一行为。
而PropertySourcesPlaceholderConfigurer在此基础上会和Environment and PropertySource配合更好。
另外需要注意以下几点
1、在PropertyPlaceholderBeanDefinitionParser的父类中shouldGenerateId返回true，即默认会为每一个bean生成一个唯一的名字； 如果使用了两个 2、PropertySourcesPlaceholderConfigurer本质是一个BeanFactoryPostProcessor，spring实施时如果发现这个bean实现了Ordered，则按照顺序执行；默认无序；
3、此时如果给 比如
此时会先扫描order='1' 的，如果没有扫描order='2'的
4、默认情况下ignore-unresolvable；即如果没找到的情况是否抛出异常。默认false：即抛出异常；
PropertyPlaceholderConfigurer内置的功能非常丰富，如果它未找到${xxx}中定义的xxx键，它还会去JVM系统属性（System.getProperty()）和环境变量（System.getenv()）中寻找。通过启用systemPropertiesMode和searchSystemEnvironment属性，开发者能够控制这一行为。
而PropertySourcesPlaceholderConfigurer在此基础上会和Environment and PropertySource配合更好。
另外需要注意以下几点
1、在PropertyPlaceholderBeanDefinitionParser的父类中shouldGenerateId返回true，即默认会为每一个bean生成一个唯一的名字； 如果使用了两个
3、此时如果给
此时会先扫描order='1' 的，如果没有扫描order='2'的
4、默认情况下ignore-unresolvable；即如果没找到的情况是否抛出异常。默认false：即抛出异常；