Issue
@Entity
@Table(name="blogs")
public class Blog {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@Column(nullable = false, length = 300)
private String title;
@Lob @Column (nullable = false)
private String body;
@Column(nullable=false)
private Date date =new Date();
@ManyToOne(optional = false,fetch = FetchType.LAZY)
@JoinColumn(name="user_id",referencedColumnName = "id", nullable= false)
private User user;
public Blog() {}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
public String getBody() {
return body;
}
public void setBody(String body) {
this.body = body;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
}
this is my Blog class
import java.awt.print.PageFormat;
import java.awt.print.Pageable;
import java.awt.print.Printable;
import java.util.List;
import java.util.Optional;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Primary;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.querydsl.QPageRequest;
import org.springframework.stereotype.Service;
@Service
@Primary
public class BlogServiceImpl implements BlogService{
@Autowired
private BlogRepository blogrepo;
@Override
public List<Blog> findAll() {
// TODO Auto-generated method stub
return this.blogrepo.findAll();
}
@Override
public List<Blog> findLatest5() {
return this.blogrepo.findLatest5Blogs(new QPageRequest(0, 5));
}
@Override
public Blog findById(Long id) {
// TODO Auto-generated method stub
return blogrepo.findById(id).get();
}
@Override
public Blog create(Blog blog) {
// TODO Auto-generated method stub
return this.blogrepo.save(blog);
}
@Override
public Blog edit(Blog blog) {
// TODO Auto-generated method stub
return this.blogrepo.save(blog);
}
@Override
public void deleteById(Long id) {
this.blogrepo.deleteById(id);;
}
}
my blogServiceImplementation
import java.awt.print.Pageable;
import java.util.List;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.querydsl.QPageRequest;
import org.springframework.stereotype.Repository;
import com.example.demo.Blog;
@Repository
public interface BlogRepository extends JpaRepository<Blog, Long>{
@Query("SELECT b FROM Blog b LEFT JOIN FETCH b.user ORDER BY b.date DESC")
List<Blog> findLatest5Blogs(QPageRequest qPageRequest);
}
my blog Repository
import java.util.ArrayList;
import java.util.List;
import javax.persistence.*;
@Entity
@Table(name = "users")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@Column(nullable = false, unique = true, length = 45)
private String email;
@Column(nullable = false, unique = true, length = 45)
private String username;
@Column(nullable = false, length = 64)
private String password;
@Column(name = "first_name", nullable = false, length = 20)
private String firstName;
@Column(name = "last_name", nullable = false, length = 20)
private String lastName;
@Column(name = "user_role")
private String user_role;
@OneToOne(cascade = CascadeType.ALL)
@JoinColumn(name="account_id")
private accountInfo accountinfo;
public User() {}
@OneToMany(mappedBy="user")
private List<Blog> blogs= new ArrayList<Blog>();
// @PrePersist
// public void prepareToInsert() {
// List<User> conflicts = find("username=?").fetch();
// if (!conflicts.isEmpty()) {
// throw new IllegalArgumentException("username `" + username + "` is already taken");
// }
// }
//
public String getUser_role() {
return user_role;
}
public void setUser_role(String user_role) {
this.user_role = user_role;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public accountInfo getAccountinfo() {
return accountinfo;
}
public void setAccountinfo(accountInfo accountinfo) {
this.accountinfo = accountinfo;
}
public List<Blog> getBlogs() {
return blogs;
}
public void setBlogs(List<Blog> blogs) {
this.blogs = blogs;
}
}
and my User class when I try to get all the Blogs its working but when i try to use the method for printing only 5 on them on 1 page Im getting this error
java.lang.ClassNotFoundException: com.querydsl.core.types.OrderSpecifier
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:602) ~[na:na]
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178) ~[na:na]
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522) ~[na:na]
at org.springframework.data.querydsl.QSort.<clinit>(QSort.java:41) ~[spring-data-commons-2.5.2.jar:2.5.2]
at org.springframework.data.querydsl.QPageRequest.<init>(QPageRequest.java:49) ~[spring-data-commons-2.5.2.jar:2.5.2]
at com.example.demo.BlogServiceImpl.findLatest5(BlogServiceImpl.java:29) ~[classes/:na]
at com.example.demo.AppController.viewKnowledge(AppController.java:86) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197) ~[spring-web-5.3.8.jar:5.3.8]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) ~[spring-web-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1063) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.8.jar:5.3.8]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:655) ~[tomcat-embed-core-9.0.48.jar:4.0.FR]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.8.jar:5.3.8]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) ~[tomcat-embed-core-9.0.48.jar:4.0.FR]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:228) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.48.jar:9.0.48]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.springframework.web.servlet.resource.ResourceUrlEncodingFilter.doFilter(ResourceUrlEncodingFilter.java:67) ~[spring-webmvc-5.3.8.jar:5.3.8]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:327) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:115) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:81) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:121) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:115) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:126) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:81) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:105) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:149) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.authentication.ui.DefaultLogoutPageGeneratingFilter.doFilterInternal(DefaultLogoutPageGeneratingFilter.java:58) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.8.jar:5.3.8]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.authentication.ui.DefaultLoginPageGeneratingFilter.doFilter(DefaultLoginPageGeneratingFilter.java:237) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.authentication.ui.DefaultLoginPageGeneratingFilter.doFilter(DefaultLoginPageGeneratingFilter.java:223) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:218) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:212) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:103) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:89) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:117) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.8.jar:5.3.8]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.header.HeaderWriterFilter.doHeadersAfter(HeaderWriterFilter.java:90) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:75) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.8.jar:5.3.8]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:110) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:80) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:55) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.8.jar:5.3.8]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:336) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:211) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:183) ~[spring-security-web-5.5.1.jar:5.5.1]
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:358) ~[spring-web-5.3.8.jar:5.3.8]
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:271) ~[spring-web-5.3.8.jar:5.3.8]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.8.jar:5.3.8]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.8.jar:5.3.8]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.8.jar:5.3.8]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.8.jar:5.3.8]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.8.jar:5.3.8]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.8.jar:5.3.8]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1723) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) ~[na:na]
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) ~[na:na]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
at java.base/java.lang.Thread.run(Thread.java:832) ~[na:na]
As far as i can tell it needs an order to print them in a page which I already did in the query in the repo.
Solution
Please, note that you are importing java.awt.print.Pageable, java.awt.print.PageFormat and java.awt.print.Printable. That could be misleading, because the pagination with Spring Data uses org.springframework.data.domain.Pageable, so I'd change those imports.
Also, a better way to use pagination in the repository is to just pass the pagination configuration using a Pageable, like this:
@Repository
public interface BlogRepository extends JpaRepository<Blog, Long>{
@Query("SELECT b FROM Blog b LEFT JOIN FETCH b.user")
List<Blog> findBlogs(Pageable pageable);
}
This way, you can call the method from the service like this:
@Override
public List<Blog> findLatest5() {
return blogrepo.findBlogs(PageRequest.of(0, 5, Sort.by("date").descending())););
}
Answered By - Gregorio Palamà
