Configuration类解析
Configuration类位于mybatis包的org.apache.ibatis.session目录下，是mybatis的全局变量，属性就是对应于mybatis的全局配置文件mybatis-config.xml的配置，将XML配置中的内容解析赋值到Configuration对象中。
由于XML配置项有很多，所以Configuration类的属性也很多。先来看下Configuration对于的XML配置文件示例：
1 <?xml version="1.0" encoding="UTF-8"?> 2 3 <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> 4 <!-- 全局配置顶级节点 --> 5 <configuration> 6 7 <!-- 属性配置,读取properties中的配置文件 --> 8 <properties resource="db.propertis"> 9 <property name="XXX" value="XXX"/> 10 </properties> 11 12 <!-- 类型别名 --> 13 <typeAliases> 14 <!-- 在用到User类型的时候,可以直接使用别名,不需要输入User类的全部路径 --> 15 <typeAlias type="com.luck.codehelp.entity.User" alias="user"/> 16 </typeAliases> 17 18 <!-- 类型处理器 --> 19 <typeHandlers> 20 <!-- 类型处理器的作用是完成JDBC类型和java类型的转换,mybatis默认已经由了很多类型处理器,正常无需自定义--> 21 </typeHandlers> 22 23 <!-- 对象工厂 --> 24 <!-- mybatis创建结果对象的新实例时,会通过对象工厂来完成，mybatis有默认的对象工厂，正常无需配置 --> 25 <objectFactory type=""></objectFactory> 26 27 <!-- 插件 --> 28 <plugins> 29 <!-- 可以自定义拦截器通过plugin标签加入 --> 30 <plugin interceptor="com.lucky.interceptor.MyPlugin"></plugin> 31 </plugins> 32 33 <!-- 全局配置参数 --> 34 <settings> 35 <setting name="cacheEnabled" value="false" /> 36 <setting name="useGeneratedKeys" value="true" /><!-- 是否自动生成主键 --> 37 <setting name="defaultExecutorType" value="REUSE" /> 38 <setting name="lazyLoadingEnabled" value="true"/><!-- 延迟加载标识 --> 39 <setting name="aggressiveLazyLoading" value="true"/><!--有延迟加载属性的对象是否延迟加载 --> 40 <setting name="multipleResultSetsEnabled" value="true"/><!-- 是否允许单个语句返回多个结果集 --> 41 <setting name="useColumnLabel" value="true"/><!-- 使用列标签而不是列名 --> 42 <setting name="autoMappingBehavior" value="PARTIAL"/><!-- 指定mybatis如何自动映射列到字段属性;NONE:自动映射;PARTIAL:只会映射结果没有嵌套的结果;FULL:可以映射任何复杂的结果 --> 43 <setting name="defaultExecutorType" value="SIMPLE"/><!-- 默认执行器类型 --> 44 <setting name="defaultFetchSize" value=""/> 45 <setting name="defaultStatementTimeout" value="5"/><!-- 驱动等待数据库相应的超时时间 ,单位是秒--> 46 <setting name="safeRowBoundsEnabled" value="false"/><!-- 是否允许使用嵌套语句RowBounds --> 47 <setting name="safeResultHandlerEnabled" value="true"/> 48 <setting name="mapUnderscoreToCamelCase" value="false"/><!-- 下划线列名是否自动映射到驼峰属性：如user_id映射到userId --> 49 <setting name="localCacheScope" value="SESSION"/><!-- 本地缓存（session是会话级别） --> 50 <setting name="jdbcTypeForNull" value="OTHER"/><!-- 数据为空值时,没有特定的JDBC类型的参数的JDBC类型 --> 51 <setting name="lazyLoadTriggerMethods" value="equals,clone,hashCode,toString"/><!-- 指定触发延迟加载的对象的方法 --> 52 <setting name="callSettersOnNulls" value="false"/><!--如果setter方法或map的put方法，如果检索到的值为null时，数据是否有用 --> 53 <setting name="logPrefix" value="XXXX"/><!-- mybatis日志文件前缀字符串 --> 54 <setting name="logImpl" value="SLF4J"/><!-- mybatis日志的实现类 --> 55 <setting name="proxyFactory" value="CGLIB"/><!-- mybatis代理工具 --> 56 </settings> 57 58 <!-- 环境配置集合 --> 59 <environments default="development"> 60 <environment id="development"> 61 <transactionManager type="JDBC"/><!-- 事务管理器 --> 62 <dataSource type="POOLED"><!-- 数据库连接池 --> 63 <property name="driver" value="com.mysql.jdbc.Driver" /> 64 <property name="url" value="jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8" /> 65 <property name="username" value="root" /> 66 <property name="password" value="*****" /> 67 </dataSource> 68 </environment> 69 </environments> 70 71 <!-- mapper文件映射配置 --> 72 <mappers> 73 <mapper resource="com/luck/codehelp/mapper/UserMapper.xml"/> 74 </mappers> 75 </configuration>
而对于XML的配置，Configuration类的属性是和XML配置对应的。Configuration类属性如下：
1 protected Environment environment;//运行环境 2 3 protected boolean safeRowBoundsEnabled = false; 4 protected boolean safeResultHandlerEnabled = true; 5 protected boolean mapUnderscoreToCamelCase = false; 6 protected boolean aggressiveLazyLoading = true; //true：有延迟加载属性的对象被调用时完全加载任意属性;false：每个属性按需要加载 7 protected boolean multipleResultSetsEnabled = true;//是否允许多种结果集从一个单独的语句中返回 8 protected boolean useGeneratedKeys = false;//是否支持自动生成主键 9 protected boolean useColumnLabel = true;//是否使用列标签 10 protected boolean cacheEnabled = true;//是否使用缓存标识 11 protected boolean callSettersOnNulls = false;// 12 protected boolean useActualParamName = true; 13 14 protected String logPrefix; 15 protected Class <? extends Log> logImpl; 16 protected Class <? extends VFS> vfsImpl; 17 protected LocalCacheScope localCacheScope = LocalCacheScope.SESSION; 18 protected JdbcType jdbcTypeForNull = JdbcType.OTHER; 19 protected Set<String> lazyLoadTriggerMethods = new HashSet<String>(Arrays.asList(new String[] { "equals", "clone", "hashCode", "toString" })); 20 protected Integer defaultStatementTimeout; 21 protected Integer defaultFetchSize; 22 protected ExecutorType defaultExecutorType = ExecutorType.SIMPLE; 23 protected AutoMappingBehavior autoMappingBehavior = AutoMappingBehavior.PARTIAL;//指定mybatis如果自动映射列到字段和属性,PARTIAL会自动映射简单的没有嵌套的结果,FULL会自动映射任意复杂的结果 24 protected AutoMappingUnknownColumnBehavior autoMappingUnknownColumnBehavior = AutoMappingUnknownColumnBehavior.NONE; 25 26 protected Properties variables = new Properties(); 27 protected ReflectorFactory reflectorFactory = new DefaultReflectorFactory(); 28 protected ObjectFactory objectFactory = new DefaultObjectFactory(); 29 protected ObjectWrapperFactory objectWrapperFactory = new DefaultObjectWrapperFactory(); 30 31 protected boolean lazyLoadingEnabled = false;//是否延时加载，false则表示所有关联对象即使加载,true表示延时加载 32 protected ProxyFactory proxyFactory = new JavassistProxyFactory(); // #224 Using internal Javassist instead of OGNL 33 34 protected String databaseId; 35 36 protected Class<?> configurationFactory; 37 38 protected final MapperRegistry mapperRegistry = new MapperRegistry(this); 39 protected final InterceptorChain interceptorChain = new InterceptorChain(); 40 protected final TypeHandlerRegistry typeHandlerRegistry = new TypeHandlerRegistry(); 41 protected final TypeAliasRegistry typeAliasRegistry = new TypeAliasRegistry(); 42 protected final LanguageDriverRegistry languageRegistry = new LanguageDriverRegistry(); 43 44 protected final Map<String, MappedStatement> mappedStatements = new StrictMap<MappedStatement>("Mapped Statements collection"); 45 protected final Map<String, Cache> caches = new StrictMap<Cache>("Caches collection"); 46 protected final Map<String, ResultMap> resultMaps = new StrictMap<ResultMap>("Result Maps collection"); 47 protected final Map<String, ParameterMap> parameterMaps = new StrictMap<ParameterMap>("Parameter Maps collection"); 48 protected final Map<String, KeyGenerator> keyGenerators = new StrictMap<KeyGenerator>("Key Generators collection"); 49 50 protected final Set<String> loadedResources = new HashSet<String>(); //已经加载过的resource(mapper) 51 protected final Map<String, XNode> sqlFragments = new StrictMap<XNode>("XML fragments parsed from previous mappers"); 52 53 protected final Collection<XMLStatementBuilder> incompleteStatements = new LinkedList<XMLStatementBuilder>(); 54 protected final Collection<CacheRefResolver> incompleteCacheRefs = new LinkedList<CacheRefResolver>(); 55 protected final Collection<ResultMapResolver> incompleteResultMaps = new LinkedList<ResultMapResolver>(); 56 protected final Collection<MethodResolver> incompleteMethods = new LinkedList<MethodResolver>(); 57 58 protected final Map<String, String> cacheRefMap = new HashMap<String, String>();
而Configuration中的方法也差不多都是关于这些属性的set和get方法。由于属性太多，就不一一解析，现在只知道Configuration类是和mybatis的XML配置是对应的。加载的过程是SqlSessionFactoryBuilder根据xml配置的文件流，通过XMLConfigBuilder的parse方法进行解析得到一个Configuration对象。那么Configuration什么时候会用到呢？