MyBatis（二） xml文件解析流程 Mapper解析

1.xml文件解析流程解析（一）里面说到在XMLConfigBuilder类中的parseConfiguration方法中来初始化整个Configuration对象，其中XMLConfigBuilder解析Mapper是在此方法的如下代码开始的。

 this.mapperElement(root.evalNode("mappers"));

2.XMLConfigBuilder类的mapperElement方法,通过mappers节点下配置的mapper等节点，并通过resourse的值，进行解析*Mapper.xml文件

private void mapperElement(XNode parent) throws Exception {
        if(parent != null) {
            Iterator i$ = parent.getChildren().iterator();
            while(true) {
  //遍历所有的mapper节点
                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 mapperInterface1;
                        if(resource != null && url == null && mapperClass == null) {
                            ErrorContext.instance().resource(resource);
                            mapperInterface1 = Resources.getResourceAsStream(resource);
                            mapperParser = new XMLMapperBuilder(mapperInterface1, this.configuration, resource, this.configuration.getSqlFragments());
                            mapperParser.parse();
                        } else if(resource == null && url != null && mapperClass == null) {
                            ErrorContext.instance().resource(url);
                            mapperInterface1 = Resources.getUrlAsStream(url);
                            mapperParser = new XMLMapperBuilder(mapperInterface1, 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.XMLMapperBuilder
上面代码中此处为获取resource并通过XMLMapperBuilder来解析文件流。

  if(resource != null && url == null && mapperClass == null) {
                            ErrorContext.instance().resource(resource);
                            mapperInterface1 = Resources.getResourceAsStream(resource);
                            mapperParser = new XMLMapperBuilder(mapperInterface1, this.configuration, resource, this.configuration.getSqlFragments());
                            mapperParser.parse();
                        } 

5.XMLMapperBuilder解析mapper配置文件。

  public void parse() {
        if(!this.configuration.isResourceLoaded(this.resource)) {
            this.configurationElement(this.parser.evalNode("/mapper"));
            this.configuration.addLoadedResource(this.resource);
            this.bindMapperForNamespace();
        }

        this.parsePendingResultMaps();
        this.parsePendingChacheRefs();
        this.parsePendingStatements();
    }

6.XMLMapperBuilder的configurationElement是真正mapper节点解析入口，包括sql解析，缓存，等。

private void configurationElement(XNode context) {
        try {
            String e = context.getStringAttribute("namespace");
            if(e.equals("")) {
                throw new BuilderException("Mapper\'s namespace cannot be empty");
            } else {
             //二级缓存相关
                this.builderAssistant.setCurrentNamespace(e);
                this.cacheRefElement(context.evalNode("cache-ref"));
                this.cacheElement(context.evalNode("cache"));
           //解析parameterMap
                this.parameterMapElement(context.evalNodes("/mapper/parameterMap"));
           //解析resultMap
                this.resultMapElements(context.evalNodes("/mapper/resultMap"));
           //解析sql节点
                this.sqlElement(context.evalNodes("/mapper/sql"));
          //解析 sql语句  
             this.buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
            }
        } catch (Exception var3) {
            throw new BuilderException("Error parsing Mapper XML. Cause: " + var3, var3);
        }
    }

7.总结：
XMLConfigBuilder负责对Mybatis的config文件进行解析入口

XMLConfigBuilder解析入口.png

而Mapper文件的解析是交给XMLMapperBuilder进行解析的。