public interface FzkRepository extends MongoRepository<Fzk, String> {
    Fzk findByName(String name);
}

@RestController
public class TestController {
    @Autowired
    private FzkRepository fzkReposiroty;
}

為什麼一個介面，沒有實現類就能被注入？

首先如果想使用MongoRepository，一定會在配置中加入@EnableMongoRepositories，就從EnableMongoRepositories開始

@Import(MongoRepositoriesRegistrar.class)

跟蹤進入RepositoryBeanDefinitionRegistrarSupport

public void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanDefinitionRegistry registry) {
....
        AnnotationRepositoryConfigurationSource configurationSource = new AnnotationRepositoryConfigurationSource(annotationMetadata, getAnnotation(), resourceLoader, environment, registry);
 

　　　　　　if (annotationMetadata.getAnnotationAttributes(getAnnotation().getName()) == null) {
　　　　　　　　return;
　　　　　　}

        RepositoryConfigurationExtension extension = getExtension();
        RepositoryConfigurationUtils.exposeRegistration(extension, registry, configurationSource);

        RepositoryConfigurationDelegate delegate 
 
= new RepositoryConfigurationDelegate(configurationSource, resourceLoader,
                environment);

        delegate.registerRepositoriesIn(registry, extension);
    }

沒什麼可說的，只有使用了EnableMongoRepositories才會繼續進行，註冊bean交給了RepositoryConfigurationDelegate 來進行。繼續進入RepositoryConfigurationDelegate.registerRepositoriesIn方法

1 public List<BeanComponentDefinition> registerRepositoriesIn(BeanDefinitionRegistry registry, 2 RepositoryConfigurationExtension extension) { 3 4 extension.registerBeansForRoot(registry, configurationSource); 5 6 RepositoryBeanDefinitionBuilder builder = new RepositoryBeanDefinitionBuilder(registry, extension, resourceLoader, 7 environment); 8 List<BeanComponentDefinition> definitions = new ArrayList<BeanComponentDefinition>(); 9 10 for (RepositoryConfiguration<? extends RepositoryConfigurationSource> configuration : extension 11 .getRepositoryConfigurations(configurationSource, resourceLoader, inMultiStoreMode)) { 12 13 BeanDefinitionBuilder definitionBuilder = builder.build(configuration); 14 15 extension.postProcess(definitionBuilder, configurationSource); 16 17 if (isXml) { 18 extension.postProcess(definitionBuilder, (XmlRepositoryConfigurationSource) configurationSource); 19 } else { 20 extension.postProcess(definitionBuilder, (AnnotationRepositoryConfigurationSource) configurationSource); 21 } 22 23 AbstractBeanDefinition beanDefinition = definitionBuilder.getBeanDefinition(); 24 String beanName = beanNameGenerator.generateBeanName(beanDefinition, registry); 25 26 if (LOGGER.isDebugEnabled()) { 27 LOGGER.debug(REPOSITORY_REGISTRATION, extension.getModuleName(), beanName, 28 configuration.getRepositoryInterface(), extension.getRepositoryFactoryClassName()); 29 } 30 31 beanDefinition.setAttribute(FACTORY_BEAN_OBJECT_TYPE, configuration.getRepositoryInterface()); 32 33 registry.registerBeanDefinition(beanName, beanDefinition); 34 definitions.add(new BeanComponentDefinition(beanDefinition, beanName)); 35 } 36 37 return definitions; 38 }

掃描實現了MongoRepository的介面並生成RepositoryConfigurationSource的邏輯在RepositoryConfigurationExtensionSupport.getRepositoryConfigurations方法中

    public <T extends RepositoryConfigurationSource> Collection<RepositoryConfiguration<T>> getRepositoryConfigurations(
            T configSource, ResourceLoader loader, boolean strictMatchesOnly) {
....
        Set<RepositoryConfiguration<T>> result = new HashSet<RepositoryConfiguration<T>>();

        for (BeanDefinition candidate : configSource.getCandidates(loader)) {
            RepositoryConfiguration<T> configuration = getRepositoryConfiguration(candidate, configSource);
            if (!strictMatchesOnly || configSource.usesExplicitFilters()) {
                result.add(configuration);
                continue;
            }
            Class<?> repositoryInterface = loadRepositoryInterface(configuration, loader);
            if (repositoryInterface == null || isStrictRepositoryCandidate(repositoryInterface)) {
                result.add(configuration);
            }
        }
        return result;
    }

繼續跟蹤RepositoryConfigurationSourceSupport.getCandidates

    public Collection<BeanDefinition> getCandidates(ResourceLoader loader) {
        RepositoryComponentProvider scanner = new RepositoryComponentProvider(getIncludeFilters(), registry);
        scanner.setConsiderNestedRepositoryInterfaces(shouldConsiderNestedRepositories());
        scanner.setEnvironment(environment);
        scanner.setResourceLoader(loader);
        for (TypeFilter filter : getExcludeFilters()) {
            scanner.addExcludeFilter(filter);
        }
        Set<BeanDefinition> result = new HashSet<BeanDefinition>();
        for (String basePackage : getBasePackages()) {
            Set<BeanDefinition> candidate = scanner.findCandidateComponents(basePackage);
            result.addAll(candidate);
        }
        return result;
    }

RepositoryComponentProvider.findCandidateComponents，先由父類ClassPathScanningCandidateComponentProvider處理

public Set<BeanDefinition> findCandidateComponents(String basePackage) {
        Set<BeanDefinition> candidates = new LinkedHashSet<BeanDefinition>();
            String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX + (basePackage) + '/' + this.resourcePattern;
            Resource[] resources = this.resourcePatternResolver.getResources(packageSearchPath);
           ......for (Resource resource : resources) {
                ......
                        MetadataReader metadataReader = this.metadataReaderFactory.getMetadataReader(resource);
                        if (isCandidateComponent(metadataReader)) {
                ......
    }

    protected boolean isCandidateComponent(MetadataReader metadataReader) throws IOException {
        for (TypeFilter tf : this.excludeFilters) {  //1
            if (tf.match(metadataReader, this.metadataReaderFactory)) {
                return false;
            }
        }
        for (TypeFilter tf : this.includeFilters) {  //2
            if (tf.match(metadataReader, this.metadataReaderFactory)) { return isConditionMatch(metadataReader); } } return false; }

　　private boolean isConditionMatch(MetadataReader metadataReader) {
　　　　if (this.conditionEvaluator == null) {
　　　　　　this.conditionEvaluator = new ConditionEvaluator(getRegistry(), getEnvironment(), getResourceLoader());
　　　　}
　　　　return !this.conditionEvaluator.shouldSkip(metadataReader.getAnnotationMetadata());
　　}

判斷條件，1.如果是註解了NoRepositoryBean就不處理，2.判斷了是Repository後，繼續判斷是否有@Condition。找到了所有複合條件的類後，組成RepositoryConfiguration後，繼續跟蹤RepositoryConfigurationDelegate.registerRepositoriesIn，組成BeanDefinitionBuilder，構件出MongoRepositoryFactoryBean。

public class MongoRepositoryFactoryBean<T extends Repository<S, ID>, S, ID extends Serializable>
        extends RepositoryFactoryBeanSupport<T, S, ID>

public abstract class RepositoryFactoryBeanSupport<T extends Repository<S, ID>, S, ID extends Serializable>
        implements InitializingBean, RepositoryFactoryInformation<S, ID>, FactoryBean<T>, BeanClassLoaderAware,
        BeanFactoryAware, ApplicationEventPublisherAware 

MongoRepositoryFactoryBean間接實現InitializingBean，因此他會實現afterPropertiesSet方法

在AbstractApplicationContext  ->  refresh()   ->   finishBeanFactoryInitialization()階段，例項化bean時進行例項化。
這個例子裡，TestController注入了FzkRepository ，例項化TestController時發現需要注入FzkRepository 會先例項化FzkRepository。
在DefaultListableBeanFactory的preInstantiateSingletons()時

public void preInstantiateSingletons() throws BeansException {
......
        for (String beanName : beanNames) {
            RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
            if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
                if (isFactoryBean(beanName)) {
                    final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
                    boolean isEagerInit;
                    if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
                        isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
                            @Override
                            public Boolean run() {
                                return ((SmartFactoryBean<?>) factory).isEagerInit();
                            }
                        }, getAccessControlContext());
                    }
                    else {
                        isEagerInit = (factory instanceof SmartFactoryBean &&
                                ((SmartFactoryBean<?>) factory).isEagerInit());
                    }
                    if (isEagerInit) {
                        getBean(beanName);
                    }
                }
                else {
                    getBean(beanName);
                }
            }
        }
......

    }

protected <T> T doGetBean(
            final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
            throws BeansException {
......
                // Create bean instance.
                if (mbd.isSingleton()) {
                    sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
                        @Override
                        public Object getObject() throws BeansException {
                            try {
                                return createBean(beanName, mbd, args);
                            }
                            catch (BeansException ex) {
......
                            }
                        }
                    });
                    bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
                }......
        return (T) bean;
    }

多次呼叫進入AbstractAutowireCapableBeanFactory.doCreateBean。

    protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
            throws BeanCreationException {
......
        // Initialize the bean instance.
        Object exposedObject = bean;
        try {
            populateBean(beanName, mbd, instanceWrapper);
            if (exposedObject != null) {
                exposedObject = initializeBean(beanName, exposedObject, mbd);
            }
        }......
    }

    protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
......
            invokeInitMethods(beanName, wrappedBean, mbd);
......
    }

protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
            throws Throwable {
......
                ((InitializingBean) bean).afterPropertiesSet();
......
    }

上面說了由BeanDefinitionBuilder構件出MongoRepositoryFactoryBean，而MongoRepositoryFactoryBean實現了InitializingBean，這裡進入到了MongoRepositoryFactoryBean.afterPropertiesSet

    public void afterPropertiesSet() {

        super.afterPropertiesSet();
        Assert.notNull(operations, "MongoTemplate must not be null!");

        if (!mappingContextConfigured) {
            setMappingContext(operations.getConverter().getMappingContext());
        }
    }

進入到父累RepositoryFactoryBeanSupport.afterPropertiesSet

    public void afterPropertiesSet() {

        this.factory = createRepositoryFactory();
......
        if (publisher != null) {
            this.factory.addRepositoryProxyPostProcessor(new EventPublishingRepositoryProxyPostProcessor(publisher));
        }

        this.repositoryMetadata = this.factory.getRepositoryMetadata(repositoryInterface);

        if (!lazyInit) {
            initAndReturn();
        }
    }

    private T initAndReturn() {
......
        if (this.repository == null) {
            this.repository = this.factory.getRepository(repositoryInterface, customImplementation);
        }
        return this.repository;
    }

這裡的factory是MongoRepositoryFactory，接下來，才是建立代理的部分

    public <T> T getRepository(Class<T> repositoryInterface, Object customImplementation) {
......
        // Create proxy
        ProxyFactory result = new ProxyFactory();
        result.setTarget(target);　
        result.setInterfaces(new Class[] { repositoryInterface, Repository.class });
......
        result.addAdvice(new QueryExecutorMethodInterceptor(information, customImplementation, target, projectionFactory));

        return (T) result.getProxy(classLoader);
    }

第一重點是ProxyFactory，這裡target是SimpleMongoRepository，repositoryInterface是FzkRepository（自己的介面）。
另一個重點是增加了一個切入點QueryExecutorMethodInterceptor。看看QueryExecutorMethodInterceptor

     public QueryExecutorMethodInterceptor(RepositoryInformation repositoryInformation, Object customImplementation,
                Object target, ProjectionFactory projectionFactory) {
......
            this.resultHandler = new QueryExecutionResultHandler();
            this.repositoryInformation = repositoryInformation;
            this.customImplementation = customImplementation;
            this.target = target;

            QueryLookupStrategy lookupStrategy = getQueryLookupStrategy(queryLookupStrategyKey,
                    RepositoryFactorySupport.this.evaluationContextProvider);
            lookupStrategy = lookupStrategy == null ? getQueryLookupStrategy(queryLookupStrategyKey) : lookupStrategy;
            Iterable<Method> queryMethods = repositoryInformation.getQueryMethods();
......
            for (Method method : queryMethods) {
                RepositoryQuery query = lookupStrategy.resolveQuery(method, repositoryInformation, projectionFactory,
                        namedQueries);

                invokeListeners(query);
                queries.put(method, query);
            }
        }

首先他是一個MethodInterceptor，一個有個invoke方法，這個方法之後在說。現在先看構造器裡幹了什麼。
首先構件一個MongoRepositoryFactory$MongoQueryLookupStrategy型別的lookupStrategy 。處理jpa寫法的方法就是由它來處理，這裡的例子是findByName方法。繼續跟蹤，看看是怎麼將findByName解析成{"name" : ***}的。寫了這麼多，終於快到終點了。繼續看，進入到MongoQueryLookupStrategy.resolveQuery

        public RepositoryQuery resolveQuery(Method method, RepositoryMetadata metadata, ProjectionFactory factory,
                NamedQueries namedQueries) {

            MongoQueryMethod queryMethod = new MongoQueryMethod(method, metadata, factory, mappingContext);
            String namedQueryName = queryMethod.getNamedQueryName();

            if (namedQueries.hasQuery(namedQueryName)) {
                String namedQuery = namedQueries.getQuery(namedQueryName);
                return new StringBasedMongoQuery(namedQuery, queryMethod, operations, EXPRESSION_PARSER,
                        evaluationContextProvider);
            } else if (queryMethod.hasAnnotatedQuery()) {
                return new StringBasedMongoQuery(queryMethod, operations, EXPRESSION_PARSER, evaluationContextProvider);
            } else {
                return new PartTreeMongoQuery(queryMethod, operations);
            }
        }

這裡，無@Query註解，進入PartTreeMongoQuery分支

    public PartTreeMongoQuery(MongoQueryMethod method, MongoOperations mongoOperations) {

        super(method, mongoOperations);

        this.processor = method.getResultProcessor();
        this.tree = new PartTree(method.getName(), processor.getReturnedType().getDomainType());
        this.isGeoNearQuery = method.isGeoNearQuery();
        this.context = mongoOperations.getConverter().getMappingContext();
    }

public class PartTree {
    private static final String KEYWORD_TEMPLATE = "(%s)(?=(\\p{Lu}|\\P{InBASIC_LATIN}))";
    private static final String QUERY_PATTERN = "find|read|get|query|stream";
    private static final String COUNT_PATTERN = "count";
    private static final String EXISTS_PATTERN = "exists";
    private static final String DELETE_PATTERN = "delete|remove";
    private static final Pattern PREFIX_TEMPLATE = Pattern.compile( //
            "^(" + QUERY_PATTERN + "|" + COUNT_PATTERN + "|" + EXISTS_PATTERN + "|" + DELETE_PATTERN + ")((\\p{Lu}.*?))??By");
    public PartTree(String source, Class<?> domainClass) {
......
        Matcher matcher = PREFIX_TEMPLATE.matcher(source);
        if (!matcher.find()) {
            this.subject = new Subject(null);
            this.predicate = new Predicate(source, domainClass);
        } else {
            this.subject = new Subject(matcher.group(0));
            this.predicate = new Predicate(source.substring(matcher.group().length()), domainClass);
        }
    }
}

最終生成的query，已經將name（key）解析出來了。

至此，終於解析完，怎麼建立的代理，怎麼根據方法名來解析sql。最後就是使用點

上面說了，使用時，會呼叫QueryExecutorMethodInterceptor.invoke

        public Object invoke(MethodInvocation invocation) throws Throwable {

            Object result = doInvoke(invocation);

            return resultHandler.postProcessInvocationResult(result, invocation.getMethod());
        }

        private Object doInvoke(MethodInvocation invocation) throws Throwable {

            Method method = invocation.getMethod();
            Object[] arguments = invocation.getArguments();

            if (isCustomMethodInvocation(invocation)) {

                Method actualMethod = repositoryInformation.getTargetClassMethod(method);
                return executeMethodOn(customImplementation, actualMethod, arguments);
            }

            if (hasQueryFor(method)) {
                return queries.get(method).execute(arguments);
            }

            // Lookup actual method as it might be redeclared in the interface
            // and we have to use the repository instance nevertheless
            Method actualMethod = repositoryInformation.getTargetClassMethod(method);
            return executeMethodOn(target, actualMethod, arguments);
        }

queries.get(method)得到PartTreeMongoQuery

    public Object execute(Object[] parameters) {

        MongoParameterAccessor accessor = new MongoParametersParameterAccessor(method, parameters);
        Query query = createQuery(new ConvertingParameterAccessor(operations.getConverter(), accessor));

        applyQueryMetaAttributesWhenPresent(query);

        ResultProcessor processor = method.getResultProcessor().withDynamicProjection(accessor);
        String collection = method.getEntityInformation().getCollectionName();

        MongoQueryExecution execution = getExecution(query, accessor,
                new ResultProcessingConverter(processor, operations, instantiators));

        return execution.execute(query, processor.getReturnedType().getDomainType(), collection);
    }

構件出Query得到結果返回