Question

在我的春季项目中，我已经实现了一个泛型类作为我所有Dao类的基础。例如，我的班级UsuarioHome有这个代码：

@Repository
public class UsuarioHome extends Dao<Usuario> {

    public UsuarioHome() {
        super(Usuario.class);
    }

}

我的泛型类有这个代码：

public class Dao<E> {

    private final E entity;

    @Autowired
    SessionFactory sessionFactory;

    protected Session getCurrentSession(){
        return sessionFactory.getCurrentSession();
    }

    public Dao(E entity) {  
        this.entity = entity;
    }

    @SuppressWarnings("unchecked")
    public Dao(Class<?> classe) {
        this.entity = (E) classe;
    }

    public E getEntity() {
        return this.entity;
    }

    @Transactional
    public boolean persist(E transientInstance) {
        try {
            sessionFactory.getCurrentSession().persist(transientInstance);
            return true;
        } catch (RuntimeException re) {
            return false;
        }
    }

    @Transactional
    public boolean remove(E transientInstance) {
        try {
            sessionFactory.getCurrentSession().delete(transientInstance);
            return true;
        } catch (RuntimeException re) {
            return false;
        }
    }

    @Transactional
    public boolean merge(E detachedInstance) {
        try {
            sessionFactory.getCurrentSession().merge(detachedInstance);
            return true;
        } catch (RuntimeException re) {
            return false;
        }
    }

    @SuppressWarnings("unchecked")
    @Transactional
    public E findById(int id) {
        try {
            E instance = (E) sessionFactory.getCurrentSession().get(entity.getClass(), id);
            return instance;
        } catch (RuntimeException re) {
            return null;
        }
    }

    @SuppressWarnings("unchecked")
    @Transactional
    public E findByField(String field, String value) {
        try {
            String expressao = entity.toString();
            String nome_classe = new String();
            StringTokenizer st = new StringTokenizer(expressao);
            while (st.hasMoreTokens()) {
                nome_classe = st.nextToken();
            }
            String query = "from "+nome_classe+" where "+field+" = :data";

            Query q = sessionFactory.getCurrentSession().createQuery(query);
            q.setParameter("data", value);
            E instance = (E) q.uniqueResult();
            return instance;
        } catch (RuntimeException re) {
            return null;
        }
    }

    @SuppressWarnings("unchecked")
    @Transactional
    public List<E> findAll() {
        try {
            List<E> instance = sessionFactory.getCurrentSession().createCriteria(entity.getClass()).list();
            return instance;
        } catch (RuntimeException re) {
            return null;
        }
    }

}

但是，当我需要从表中检索所有项目的列表时，我收到的是0项。执行此操作的方法放在我的班级UsuarioService：

中

@Transactional
public List<Usuario> listagem_usuarios() {
    return usuario.findAll();
}

我自动登上Dao课程：

@Autowired
private UsuarioHome usuario;

@Autowired
private GrupoPermissaoHome grupo_permissao;

任何人都可以告诉我这里做错了什么？我在其他项目中测试了这个解决方案（比这简单），并且它可以工作。

更新

当我尝试运行应用程序时，我正面临一个强制转换错误，例如，当打开这个json页面时，这样做：

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="json" uri="http://www.atg.com/taglibs/json" %>
<json:object>
<c:forEach var="item" items="${lista}">
      <json:object name="usuario">
         <json:property name="id" value="${item.id}"/>
         <json:property name="login" value="${item.login}"/>
         <json:property name="pnome" value="${item.first_name}"/>
         <json:property name="unome" value="${item.last_name}"/>
         <json:property name="email" value="${item.email}"/>
      </json:object>
</c:forEach>
</json:object>

控制台显示此错误：

Grave: Servlet.service() for servlet jsp threw exception
java.lang.NumberFormatException: For input string: "id"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:492)
    at java.lang.Integer.parseInt(Integer.java:527)
    at javax.el.ArrayELResolver.coerce(ArrayELResolver.java:166)
    at javax.el.ArrayELResolver.getValue(ArrayELResolver.java:46)
    at org.apache.jasper.el.JasperELResolver.getValue(JasperELResolver.java:104)
    at org.apache.el.parser.AstValue.getValue(AstValue.java:183)
    at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:185)
    at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:1026)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp._jspx_meth_json_005fproperty_005f0(listagem_005fusuarios_jsp.java:168)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp.access$1(listagem_005fusuarios_jsp.java:156)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp$Helper.invoke1(listagem_005fusuarios_jsp.java:271)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp$Helper.invoke(listagem_005fusuarios_jsp.java:310)
    at atg.taglib.json.JsonObjectTag.doTag(JsonObjectTag.java:63)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp._jspx_meth_json_005fobject_005f1(listagem_005fusuarios_jsp.java:151)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp._jspx_meth_c_005fforEach_005f0(listagem_005fusuarios_jsp.java:117)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp.access$0(listagem_005fusuarios_jsp.java:98)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp$Helper.invoke0(listagem_005fusuarios_jsp.java:261)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp$Helper.invoke(listagem_005fusuarios_jsp.java:307)
    at atg.taglib.json.JsonObjectTag.doTag(JsonObjectTag.java:63)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp._jspx_meth_json_005fobject_005f0(listagem_005fusuarios_jsp.java:93)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp._jspService(listagem_005fusuarios_jsp.java:68)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:749)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:487)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:412)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:339)
    at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:238)
    at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:263)
    at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1208)
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:992)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:939)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:146)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:154)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:199)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:57)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)

Mai 20, 2014 7:40:22 AM org.apache.catalina.core.StandardWrapperValve invoke
Grave: Servlet.service() for servlet [json_dispatcher] in context with path [/loja] threw exception [An exception occurred processing JSP page /WEB-INF/view/json/listagem_usuarios.jsp at line 5

2: <%@ taglib prefix="json" uri="http://www.atg.com/taglibs/json" %>
3: <json:object>
4: <c:forEach var="item" items="${lista}">
5:    <json:object name="usuario">
6:       <json:property name="id" value="${item.id}"/>
7:       <json:property name="login" value="${item.login}"/>
8:       <json:property name="pnome" value="${item.first_name}"/>


Stacktrace:] with root cause
java.lang.NumberFormatException: For input string: "id"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:492)
    at java.lang.Integer.parseInt(Integer.java:527)
    at javax.el.ArrayELResolver.coerce(ArrayELResolver.java:166)
    at javax.el.ArrayELResolver.getValue(ArrayELResolver.java:46)
    at org.apache.jasper.el.JasperELResolver.getValue(JasperELResolver.java:104)
    at org.apache.el.parser.AstValue.getValue(AstValue.java:183)
    at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:185)
    at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:1026)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp._jspx_meth_json_005fproperty_005f0(listagem_005fusuarios_jsp.java:168)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp.access$1(listagem_005fusuarios_jsp.java:156)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp$Helper.invoke1(listagem_005fusuarios_jsp.java:271)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp$Helper.invoke(listagem_005fusuarios_jsp.java:310)
    at atg.taglib.json.JsonObjectTag.doTag(JsonObjectTag.java:63)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp._jspx_meth_json_005fobject_005f1(listagem_005fusuarios_jsp.java:151)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp._jspx_meth_c_005fforEach_005f0(listagem_005fusuarios_jsp.java:117)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp.access$0(listagem_005fusuarios_jsp.java:98)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp$Helper.invoke0(listagem_005fusuarios_jsp.java:261)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp$Helper.invoke(listagem_005fusuarios_jsp.java:307)
    at atg.taglib.json.JsonObjectTag.doTag(JsonObjectTag.java:63)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp._jspx_meth_json_005fobject_005f0(listagem_005fusuarios_jsp.java:93)
    at org.apache.jsp.WEB_002dINF.view.json.listagem_005fusuarios_jsp._jspService(listagem_005fusuarios_jsp.java:68)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:749)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:487)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:412)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:339)
    at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:238)
    at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:263)
    at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1208)
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:992)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:939)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:146)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:154)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:199)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:57)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:343)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:260)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)

更新2

经过更多测试后，我在使用时验证：

List<E> instance = sessionFactory.getCurrentSession().createCriteria(entity.getClass()).list();

我得到一个空列表。但是当我使用：

List<E> instance = (List<E>) sessionFactory.getCurrentSession().createSQLQuery("select * from usuario").list();

我从数据库中获取数据，但由于出现了强制转换错误（我在第一次更新中进行了解释），我可以访问它们。

ps：其他方法findById和findByField工作正常。

Answer 1

好的，我按照本主题的建议解决了这个问题：

Class derived from generic class don't get the correct type

Dao模板的最终代码是：

public class Dao<E> {

    private final Class<E> entity;

    @Autowired
    protected SessionFactory sessionFactory;

    protected Session getCurrentSession(){
        return sessionFactory.getCurrentSession();
    }

    /*public Dao(E entity) {  
        this.entity = entity;
    }*/

    public Dao(Class<E> classe) {
        this.entity = classe;
    }

    /*public E getEntity() {
        return this.entity;
    }*/

    @Transactional
    public boolean persist(E transientInstance) {
        sessionFactory.getCurrentSession().persist(transientInstance);
        return true;
    }

    @Transactional
    public boolean remove(E transientInstance) {
        sessionFactory.getCurrentSession().delete(transientInstance);
        return true;
    }

    @Transactional
    public boolean merge(E detachedInstance) {
        sessionFactory.getCurrentSession().merge(detachedInstance);
        return true;
    }

    @Transactional
    public E findById(int id) {
        E instance = (E) sessionFactory.getCurrentSession().get(entity.getClass(), id);
        return instance;
    }

    @Transactional
    public E findByField(String field, String value) {
        String expressao = entity.toString();
        String nome_classe = new String();
        StringTokenizer st = new StringTokenizer(expressao);
        while (st.hasMoreTokens()) {
            nome_classe = st.nextToken();
        }
        String query = "from "+nome_classe+" where "+field+" = :data";

        Query q = sessionFactory.getCurrentSession().createQuery(query);
        q.setParameter("data", value);
        E instance = (E) q.uniqueResult();
        return instance;
    }

    @Transactional
    public List<E> findAll() {
        return (List<E>) sessionFactory.getCurrentSession().createCriteria(entity).setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY).list();
    }

}

java.lang.ClassCastException：[Ljava.lang.Object;无法转换为com.spring.webapp.lojavirtual.acesso.persistence.model.Usuario

1 个答案: