一、最近努力可好？
二、
springMVC通过Dispactcher类就行分发，由doService--->doDispatch
/**
* Exposes the DispatcherServlet-specific request attributes and delegates to {@link #doDispatch}
* for the actual dispatching.
*/
@Override
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
if (logger.isDebugEnabled()) {
String resumed = WebAsyncUtils.getAsyncManager(request).hasConcurrentResult() ? " resumed" : "";
logger.debug("DispatcherServlet with name '" + getServletName() + "'" + resumed +
" processing " + request.getMethod() + " request for [" + getRequestUri(request) + "]");
}
// Keep a snapshot of the request attributes in case of an include,
// to be able to restore the original attributes after the include.
Map<String, Object> attributesSnapshot = null;
if (WebUtils.isIncludeRequest(request)) {
attributesSnapshot = new HashMap<String, Object>();
Enumeration<?> attrNames = request.getAttributeNames();
while (attrNames.hasMoreElements()) {
String attrName = (String) attrNames.nextElement();
if (this.cleanupAfterInclude || attrName.startsWith("org.springframework.web.servlet")) {
attributesSnapshot.put(attrName, request.getAttribute(attrName));
}
}
}
// Make framework objects available to handlers and view objects.
request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext());
request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver);
request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver);
request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource());
FlashMap inputFlashMap = this.flashMapManager.retrieveAndUpdate(request, response);
if (inputFlashMap != null) {
request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap));
}
request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap());
request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager);
try {
doDispatch(request, response);//重点在此方法
}
finally {
if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
// Restore the original attribute snapshot, in case of an include.
if (attributesSnapshot != null) {
restoreAttributesAfterInclude(request, attributesSnapshot);
}
}
}
}
我们来看看doDispatch(?,?)方法
重点分以下几个步骤看
1）根据请求路径查找HandlerExecutionChain
2）根据对应的handler找到相应的操作适配器
3）调用相关方法
4）根据返回类型来处理返回值
2.1、HandlerExecutionChain的获取
mappedHandler = getHandler(processedRequest);
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
for (HandlerMapping hm : this.handlerMappings) {
if (logger.isTraceEnabled()) {
logger.trace(
"Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");
}
HandlerExecutionChain handler = hm.getHandler(request);
if (handler != null) {
return handler;
}
}
return null;
}
看下面的方法中再循环this.handlerMappings，那么我们首先就想到handlerMappings这个列表的值是哪里来的，再Dispatcher.java中我们看看到这个方法initHandlerMappings，是在启动的时候initStrategies方法中调用的
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null;
//判断是否查找所有Spring中所有的HandlerMapping,查找到后按照order进行排序
if (this.detectAllHandlerMappings) {
// Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
Map<String, HandlerMapping> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerMappings = new ArrayList<HandlerMapping>(matchingBeans.values());
// We keep HandlerMappings in sorted order.
AnnotationAwareOrderComparator.sort(this.handlerMappings);
}
}
else {//指定类型获取对应的HandlerMapping
try {
HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
this.handlerMappings = Collections.singletonList(hm);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we'll add a default HandlerMapping later.
}
if (this.handlerMappings == null) {
this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
if (logger.isDebugEnabled()) {
logger.debug("No HandlerMappings found in servlet '" + getServletName() + "': using default");
}
}
}
这里初始化的代码说明只说下最后的一个判断空的处理，如果获取的是空的，那么就找默认的，我们可以看到getDefaultStrategies方法中是从defaultStrategies中获取,从默认的DispatcherServlet.properties中读取
static {
try {
ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, DispatcherServlet.class);
defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
}
catch (IOException ex) {
throw new IllegalStateException("Could not load 'DispatcherServlet.properties': " + ex.getMessage());
}
}
default
所以再看源码的时候，首先先理解代码中的每个数据怎么来的。继续看HandlerMappings里面是怎么获取的。
我们继续往下看
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
Object handler = getHandlerInternal(request);
if (handler == null) {
handler = getDefaultHandler();
}
if (handler == null) {
return null;
}
// Bean name or resolved handler?
if (handler instanceof String) {
String handlerName = (String) handler;
handler = getApplicationContext().getBean(handlerName);
}
//获取拦截器放入相应拦截器列表，在执行方法前调用拦截器preHandle方法
HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
if (CorsUtils.isCorsRequest(request)) {
CorsConfiguration globalConfig = this.corsConfigSource.getCorsConfiguration(request);
CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
}
return executionChain;
}
此时
Object handler = getHandlerInternal(request);
image.png
这里下拉框可以看出有三个子类中有这个方法，那么我们应该执行那个了？我们知道当前对象是RequestMappingHandlerMapping类，所以看继承结构图handleStruts.png
handle
handleStruts.png
在lookupHandlerMethod方法中我们可以看到从mappingRegistry中根据URL获取对应的数据
List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
image.png
HandleMapping处理器映射器的查找完成，并HandlerExecutionChain中还包含了拦截器的相关信息，在执行方法前，方法后会调用拦截器的相关方法。
接着就是处理器适配器
2.2、HandlerAdapter处理适配器的获取
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
我们看到具体方法
protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
for (HandlerAdapter ha : this.handlerAdapters) {
if (logger.isTraceEnabled()) {
logger.trace("Testing handler adapter [" + ha + "]");
}
if (ha.supports(handler)) {
return ha;
}
}
throw new ServletException("No adapter for handler [" + handler +
"]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler");
}
可以看到，会调用相关的support方法来进行判断是否支持
我们看看AbstractHandlerMethodAdapter类
public final boolean supports(Object handler) {
return (handler instanceof HandlerMethod && supportsInternal((HandlerMethod) handler));
}
在获取HandlerExecutionChain中的handler是HandlerMethod类型，所以最后匹配看如下图片，匹配到RequestMappingHandlerAdapter，其父类AbstractHandlerMethodAdapter中的方法如上述代码所示。
image.png
RequestMappingHandlerAdapter.png
2.3、拦截器preHandle方法调用
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
上述代码就是触发拦截器的preHandle方法
2.4、controller中方法调用
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
image.png
可以看到具体调用的方法流程如下图
flow.png
AbstractMessageConverterMethodProcessor.java
image.png
三、思路
java.lang.IllegalArgumentException: No converter found for return value of type: class com.mouse.moon.Vo.Person
at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:178) ~[spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:153) ~[spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:165) ~[spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:80) ~[spring-web-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:126) ~[spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:814) ~[spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:737) ~[spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) ~[spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) ~[spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:624) [servlet-api.jar:na]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:731) [servlet-api.jar:na]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303) [catalina.jar:7.0.64]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) [catalina.jar:7.0.64]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat7-websocket.jar:7.0.64]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) [catalina.jar:7.0.64]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) [catalina.jar:7.0.64]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:121) [spring-web-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.3.RELEASE.jar:4.2.3.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) [catalina.jar:7.0.64]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) [catalina.jar:7.0.64]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220) [catalina.jar:7.0.64]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122) [catalina.jar:7.0.64]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505) [catalina.jar:7.0.64]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170) [catalina.jar:7.0.64]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103) [catalina.jar:7.0.64]
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956) [catalina.jar:7.0.64]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) [catalina.jar:7.0.64]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423) [catalina.jar:7.0.64]
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079) [tomcat-coyote.jar:7.0.64]
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625) [tomcat-coyote.jar:7.0.64]
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316) [tomcat-coyote.jar:7.0.64]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [na:1.7.0_79]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [na:1.7.0_79]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-coyote.jar:7.0.64]
at java.lang.Thread.run(Thread.java:745) [na:1.7.0_79]
https://blog.csdn.net/weixin_37647084/article/details/59103885
