mybatis 源码分析一

1.SqlSessionFactoryBuilder 

public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
        SqlSessionFactory var5;
        try {//通过XML
            XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
            var5 = this.build(parser.parse());
        } catch (Exception var14) {
            throw ExceptionFactory.wrapException("Error building SqlSession.", var14);
        } finally {
            ErrorContext.instance().reset();

            try {
                inputStream.close();
            } catch (IOException var13) {
                ;
            }

        }

        return var5;
    }

public SqlSessionFactory build(Configuration config) {
    return new DefaultSqlSessionFactory(config);
}

2.BaseBuilder

public abstract class BaseBuilder {
    protected final Configuration configuration;
    protected final TypeAliasRegistry typeAliasRegistry;
    protected final TypeHandlerRegistry typeHandlerRegistry;

    public BaseBuilder(Configuration configuration) {
        this.configuration = configuration;
        this.typeAliasRegistry = this.configuration.getTypeAliasRegistry();
        this.typeHandlerRegistry = this.configuration.getTypeHandlerRegistry();
    }
    ...
}

3.XMLConfigBuilder extends BaseBuilder

public Configuration parse() {
        if (this.parsed) {
            throw new BuilderException("Each MapperConfigParser can only be used once.");
        } else {
            this.parsed = true;
            this.parseConfiguration(this.parser.evalNode("/configuration"));
            return this.configuration;
        }
    }

    private void parseConfiguration(XNode root) {
        try {
            this.propertiesElement(root.evalNode("properties"));
            this.typeAliasesElement(root.evalNode("typeAliases"));
            this.pluginElement(root.evalNode("plugins"));
            this.objectFactoryElement(root.evalNode("objectFactory"));
            this.objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
            this.settingsElement(root.evalNode("settings"));
            this.environmentsElement(root.evalNode("environments"));
            this.databaseIdProviderElement(root.evalNode("databaseIdProvider"));
            this.typeHandlerElement(root.evalNode("typeHandlers"));
//解析mappers指定的映射文件，将MapperStatement信息加载至configuration
            this.mapperElement(root.evalNode("mappers"));
        } catch (Exception var3) {
            throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + var3, var3);
        }
    }

根据指定mapper映射文件的方式对mappers标签进行解析

<mappers>

　　<mapper resource="com/abc/dao/mapper.xml"/>

</mappers>

<mappers>

　　<mapper url="file:///E:\workspace\com/abc/dao/mapper.xml"/>

</mappers>

<mappers>

　　<mapper class="com.abc.dao.IStudentDao"/>

</mappers>

<mappers>

　　<mapper package="com.abc.dao"/>

</mappers>

private void mapperElement(XNode parent) throws Exception {
        if (parent != null) {
            Iterator i$ = parent.getChildren().iterator();

            while(true) {
                while(i$.hasNext()) {
                    XNode child = (XNode)i$.next();
                    String resource;
                    if ("package".equals(child.getName())) {
                        resource = child.getStringAttribute("name");
                        this.configuration.addMappers(resource);
                    } else {
                        resource = child.getStringAttribute("resource");
                        String url = child.getStringAttribute("url");
                        String mapperClass = child.getStringAttribute("class");
                        XMLMapperBuilder mapperParser;
                        InputStream inputStream;
                        if (resource != null && url == null && mapperClass == null) {
                            ErrorContext.instance().resource(resource);
                            inputStream = Resources.getResourceAsStream(resource);
                            mapperParser = new XMLMapperBuilder(inputStream, this.configuration, resource, this.configuration.getSqlFragments());
                            mapperParser.parse();
                        } else if (resource == null && url != null && mapperClass == null) {
                            ErrorContext.instance().resource(url);
                            inputStream = Resources.getUrlAsStream(url);
                            mapperParser = new XMLMapperBuilder(inputStream, this.configuration, url, this.configuration.getSqlFragments());
                            mapperParser.parse();
                        } else {
                            if (resource != null || url != null || mapperClass == null) {
                                throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");
                            }

                            Class<?> mapperInterface = Resources.classForName(mapperClass);
                            this.configuration.addMapper(mapperInterface);
                        }
                    }
                }

                return;
            }
        }
    }

4.Configuration & MapperRegistry

public class Configuration {
    protected MapperRegistry mapperRegistry; //存储每个接口的mapper文件对应的类
    protected final Map<String, MappedStatement> mappedStatements; //存储由namespace 和sql id 能唯一确定的
　　sql语句对应的sql节点信息
    ...
}

public class MapperRegistry {
    private Configuration config;
    private final Map<Class<?>, MapperProxyFactory<?>> knownMappers = new HashMap();

    public MapperRegistry(Configuration config) {
        this.config = config;
    }

    public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
        MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory)this.knownMappers.get(type);
        if (mapperProxyFactory == null) {
            throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
        } else {
            try {
                return mapperProxyFactory.newInstance(sqlSession);
            } catch (Exception var5) {
                throw new BindingException("Error getting mapper instance. Cause: " + var5, var5);
            }
        }
    }

    public <T> boolean hasMapper(Class<T> type) {
        return this.knownMappers.containsKey(type);
    }

    public <T> void addMapper(Class<T> type) {
        if (type.isInterface()) {
            if (this.hasMapper(type)) {
                throw new BindingException("Type " + type + " is already known to the MapperRegistry.");
            }

            boolean loadCompleted = false;

            try {
                this.knownMappers.put(type, new MapperProxyFactory(type));
                MapperAnnotationBuilder parser = new MapperAnnotationBuilder(this.config, type);
                parser.parse();
                loadCompleted = true;
            } finally {
                if (!loadCompleted) {
                    this.knownMappers.remove(type);
                }
            }
        }
    }
}

　

5.建造者模式

一个对象的参数太过于复杂，就不再适于通过构造函数的方式创建对象，而通过建造者模式对该对象的每个参数分别组建

6.DefaultSqlSession和DefaultSqlSessionFactory

private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
        Transaction tx = null;

        DefaultSqlSession var8;
        try {
            Environment environment = this.configuration.getEnvironment();
            TransactionFactory transactionFactory = this.getTransactionFactoryFromEnvironment(environment);
            tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
            Executor executor = this.configuration.newExecutor(tx, execType, autoCommit);
            var8 = new DefaultSqlSession(this.configuration, executor);
        } catch (Exception var12) {
            this.closeTransaction(tx);
            throw ExceptionFactory.wrapException("Error opening session.  Cause: " + var12, var12);
        } finally {
            ErrorContext.instance().reset();
        }

        return var8;
    }