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POJPA criteria query load entire table
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  1. POJPA criteria query load entire table
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    copied!<p>I feel like this is a silly question, but I can't find the answer. I have a class as follows:</p> <pre><code>import java.io.Serializable; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.SequenceGenerator; import javax.persistence.Table; @Entity @Table(name="DEMO_VARIABLES") public class Variable implements Serializable { private static final long serialVersionUID = -1734898766626582592L; @Id @SequenceGenerator(name="VARIABLE_ID_GENERATOR", sequenceName="DEMO_VARIABLE_ID_SEQ", allocationSize=1) @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="VARIABLE_ID_GENERATOR") @Column(name="VARIABLE_ID", unique=true, nullable=false, precision=22) private long variableId; @Column(name="VARIABLE_NAME", nullable=false, length=50) private String variableName; @Column(name="VARIABLE_VALUE", nullable=false, length=500) private String variableValue; public Variable() { } public long getVariableId() { return variableId; } public void setVariableId(long variableId) { this.variableId = variableId; } public String getVariableName() { return variableName; } public void setVariableName(String variableName) { this.variableName = variableName; } public String getVariableValue() { return variableValue; } public void setVariableValue(String variableValue) { this.variableValue = variableValue; } } </code></pre> <p>Now I want to use a criteria query to load the entire table (ie "select * from variables"). I'd like to use a criteria query more for code consistency than anything else. I get this exception though: </p> <pre><code>java.lang.IllegalStateException: No criteria query roots were specified at org.hibernate.ejb.criteria.CriteriaQueryImpl.validate(CriteriaQueryImpl.java:303) at org.hibernate.ejb.criteria.CriteriaQueryCompiler.compile(CriteriaQueryCompiler.java:145) at org.hibernate.ejb.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:437 </code></pre> <p>The query I am using is:</p> <pre><code>public List&lt;Variable&gt; loadAllVariables() { CriteriaBuilder builder = em.getCriteriaBuilder(); CriteriaQuery&lt;Variable&gt; query = builder.createQuery(Variable.class); return em.createQuery(query).getResultList(); } </code></pre> <p>I know that the exception means it wants this:</p> <pre><code>Root&lt;Variable&gt; variableRoot = query.from(Variable.class); </code></pre> <p>But without a Predicate I don't see how to get the Root object into the query?</p>
 

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