解决java.lang.IllegalArgumentException: No converter found for return value of type: class java.util.ArrayList问题
在spring + springmvc + mybatis框架中，我们配置接口对外返回json格式，但是报如下错误：
1 24-Oct-2017 17:42:23.495 严重 [http-nio-8080-exec-6] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.IllegalArgumentException: No converter found for return value of type: class java.util.ArrayList] with root cause 2 java.lang.IllegalArgumentException: No converter found for return value of type: class java.util.ArrayList 3 at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:187) 4 at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:174) 5 at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:81) 6 at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:113) 7 at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) 8 at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) 9 at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) 10 at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967) 11 at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901) 12 at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) 13 at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) 14 at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) 15 at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) 16 at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) 17 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) 18 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) 19 at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) 20 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) 21 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) 22 at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) 23 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 24 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) 25 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) 26 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) 27 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:108) 28 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) 29 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) 30 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) 31 at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620) 32 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) 33 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) 34 at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:784) 35 at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) 36 at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:802) 37 at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1410) 38 at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) 39 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) 40 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) 41 at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) 42 at java.lang.Thread.run(Thread.java:745)
经过度娘，因为springmvc默认是没有对象转换成json的转换器的，需要手动添加jackson依赖。
因此，在build.gradle中加入：
1 compile group: 'com.fasterxml.jackson.core', name: 'jackson-core', version: '2.8.8' 2 // https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind 3 compile group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '2.8.8' 4 // https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations 5 compile group: 'com.fasterxml.jackson.core', name: 'jackson-annotations', version: '2.8.8'
如果maven，加入：
手动添加jackson依赖到pom.xml文件中
<properties>
<jackson.version>2.5.4</jackson.version>
</properties>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>${jackson.version}</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>${jackson.version}</version>
</dependency>
如果还是没有解决，则进行以下步骤
在springmvc配置文件中进行如下配置
<mvc:annotation-driven>
<mvc:message-converters>
<bean class="org.springframework.http.converter.StringHttpMessageConverter"/>
<bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"/>
</mvc:message-converters>
</mvc:annotation-driven>
