[JAVA] What I did when JSF couldn't display database information in the view

About the problem that `` `javax.ejb.EJBException``` appears when trying to display database information in the view. I tried to summarize what I did until the solution as a memorandum.

What you are using

• mac PC
• NetBeans 11.0
• GlassFish Server 4.1.1
• JSF(Java Server Faces) 2.2

What you want to do & problems

① Save the entered value in the database ② Display the information saved in the database on the page

problem

When I executed ② with the following code, I got an error `` `javax.ejb.EJBException```.

index.xhtml (Below the body tag)

        <h2>Data creation</h2>
        <h:form>
            <h:panelGrid columns="2">
number:             
                <h:inputText value ="#{backigBean.number}" />
name:
                <h:inputText value ="#{backigBean.name}" />
                <h:commandButton value="Create" action="#{backigBean.create}" />
                <h:commandButton value="cancel" type="reset" />
            </h:panelGrid>
            <br/>
            <br/>
            <h2>List of created information</h2>
            <h:dataTable value="#{backigBean.getAll}" var="item">
                <h:column>#{item.number}</h:column>
                <h:column>#{item.name}</h:column>
                <h:column><h:commandLink value="Edit" action="#{backigBean.toReturn}" /></h:column>
                <h:column><h:commandButton value="Delete" action="#{backigBean.delete(item)}" /></h:column>
            </h:dataTable>
            <h:commandButton value="Return" action="#{backigBean.toReturn}" />
        </h:form>

BackingBean.java (Business logic code)

package backingBeans;

import ejb.DataManager;
import entity.Data;
import java.io.Serializable;
import java.util.List;
import javax.ejb.EJB;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;

@SessionScoped
@ManagedBean
public class BackingBean implements Serializable{
    private Integer number;
    private String name;
    @EJB
    private DataManager dm;
    
    //Data storage
    public String create(){
        Data data = new Data();
        data.setNumber(number);
        data.setName(name);
        if(number == null) return null;
        try{
             dm.create(data);
        }catch(javax.ejb.EJBException e){}     
        clear();
        return null;
    }

    //Get all data from DB
    public List<Data> getAll(){
        return dm.getAll();
    }

    //Delete data
    public String delete(Data data){
        dm.delete(data);
        return null;
    }

    //Clear browser
     public void clear(){
        number = null;
        name = null;
    }
    
    //Return to the same page
    public String toReturn(){
        return null;
    }
    
    //Getters & Setters
    public Integer getNumber() {
        return number;
    }
    public void setNumber(Integer number) {
        this.number = number;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

Data.java (Data class)

package entity;

import java.io.Serializable;
import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class Data implements Serializable{
    @Id
    private Integer number;
    private String name;
    public Data(){}
    public Data(Integer number, String name){
        this.number = number;
        this.name = name;
    }

    //Getters & Setters
    public Integer getNumber() {
        return number;
    }
    public void setNumber(Integer number) {
        this.number = number;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

DataManager.java (Code that mediates between DB and data)

package ejb;

import entity.Data;
import java.util.List;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;


@Stateless
public class DataManager {
    @PersistenceContext
    private EntityManager em;
    
    //Save input value in DB
    public void create(Data data){
        em.persist(data);
    }
    //Delete data on DB
    public void delete(Data data){
        em.remove(em.merge(data));
    }
    //Get all the data on the DB
    public List<Data> getAll(){
        return em.createNamedQuery("backingBean.getAll").getResultList();
    }
    
}

3 things I tried to solve

1. Clear the cache

Terminal

$ ~/Library/Caches
$ rm -rf NetBeans 

Then restart NetBeans. ... but nothing changed. (Reference site: http://d.hatena.ne.jp/tkrd/20140818/1408315483)

2. Narrow down the resources tag in `` `glassfish-resources.xhtml``` to one

glassfish-resources.xhtml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE resources PUBLIC "-//GlassFish.org//DTD GlassFish Application Server 3.1 Resource Definitions//EN" "http://glassfish.org/dtds/glassfish-resources_1_5.dtd">
<resources>
    <jdbc-connection-pool allow-non-component-callers="false" associate-with-thread="false" connection-creation-retry-attempts="0" connection-creation-retry-interval-in-seconds="10" connection-leak-reclaim="false" connection-leak-timeout-in-seconds="0" connection-validation-method="auto-commit" datasource-classname="org.apache.derby.jdbc.ClientDataSource" fail-all-connections="false" idle-timeout-in-seconds="300" is-connection-validation-required="false" is-isolation-level-guaranteed="true" lazy-connection-association="false" lazy-connection-enlistment="false" match-connections="false" max-connection-usage-count="0" max-pool-size="32" max-wait-time-in-millis="60000" name="derby_net_test_appPool" non-transactional-connections="false" pool-resize-quantity="2" res-type="javax.sql.DataSource" statement-timeout-in-seconds="-1" steady-pool-size="8" validate-atmost-once-period-in-seconds="0" wrap-jdbc-objects="false">
        <property name="serverName" value="localhost"/>
        <property name="portNumber" value="1527"/>
        <property name="databaseName" value="test"/>
        <property name="User" value="testuser"/>
        <property name="Password" value="test"/>
        <property name="URL" value="jdbc:derby://localhost:1527/test"/>
        <property name="driverClass" value="org.apache.derby.jdbc.ClientDriver"/>
    </jdbc-connection-pool>
    <jdbc-resource enabled="true" jndi-name="java:app/jdbc/test" object-type="user" pool-name="derby_net_test_appPool"/>
</resources>

Perhaps in this resource tag, it says, "In this project, the server will connect to this database." When I connect to multiple databases, a lot of database information is automatically generated, so the server doesn't know which database to connect to ... I think. So edit the resource tag so that it appears only once in this file.

This solves the server problem!

3. Change the function to use

This time I got another error. It seems that getAll is not good, so change the relevant part of the view file to all.

index.xhtml

...(abridgement)
<h2>List of created information</h2>
<h:dataTable value="#{backigBean.all}" var="item">

Then, `javax.ejb.EJBException` will appear again. Therefore, change the code of DataManager to the following function.

DataManager

 //...(abridgement)
 //Get all the data on the DB
    public List<Data> getAll(){
         //return em.createNamedQuery("backingBean.getAll").getResultList();Change here to
         return em.createQuery("SELECT c FROM Data c").getResultList();
    }

moved! !!

Summary

• There is a file that sets the association between the server, Model (database), View (front), and Controller (internal system). If you think "Oh, that's strange", make sure those files are consistent.
• If you look only at the letter of the error, it may not be solved for the rest of your life. If you have code that you are using without knowing it, you can doubt it.