获取 Mapper 接口

• 解析配置文件

  SqlSessionBuilder 接口

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

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

        }

        return var5;
    }

XMLConfigBuilder

public Configuration parse() {
        // 配置文件只被解析一次
        if (this.parsed) {
            throw new BuilderException("Each XMLConfigBuilder can only be used once.");
        } else {
            this.parsed = true;
            // 解析
            this.parseConfiguration(this.parser.evalNode("/configuration"));
            return this.configuration;
        }
    }
        

private void parseConfiguration(XNode root) {
        try {
            this.propertiesElement(root.evalNode("properties"));
            Properties settings = this.settingsAsProperties(root.evalNode("settings"));
            this.loadCustomVfs(settings);
            this.typeAliasesElement(root.evalNode("typeAliases"));
            this.pluginElement(root.evalNode("plugins"));
            this.objectFactoryElement(root.evalNode("objectFactory"));
            this.objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
            this.reflectorFactoryElement(root.evalNode("reflectorFactory"));
            this.settingsElement(settings);
            this.environmentsElement(root.evalNode("environments"));
            this.databaseIdProviderElement(root.evalNode("databaseIdProvider"));
            this.typeHandlerElement(root.evalNode("typeHandlers"));
            // 获取 mapper 接口
            this.mapperElement(root.evalNode("mappers"));
        } catch (Exception var3) {
            throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + var3, var3);
        }
    }

private void mapperElement(XNode parent) throws Exception {
        if (parent != null) {
            Iterator var2 = parent.getChildren().iterator();

            // mappers 标签配置 mapper 资源的三种方式
            while(true) {
                while(var2.hasNext()) {
                    XNode child = (XNode)var2.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);
                            // 注册 mapper 接口到 MapperRegistry
                            this.configuration.addMapper(mapperInterface);
                        }
                    }
                }

                return;
            }
        }
    }

mapper 接口编程首先要获取 mapper 接口信息，因此必须解析配置文件获取 所有 mapper 接口

• 序列图：

  
  maper 接口注册