[Java]@Index用法——javax.persistence.Index

package com.springup.utiku.model;import java.io.Serializable;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.Index;import javax.persistence.Table;@Entity@Table(indexes = {         @Index(name="studentAnswerQueIdIndex", columnList="studentAnswerQueId DESC"),        @Index(name="questionConIdIndex", columnList="questionConId")         })public class StudentAnswerConEntity implements Serializable {    private static final long serialVersionUID = 1L;    @Id    @GeneratedValue(strategy=GenerationType.AUTO)    private Long id;    private Long studentAnswerQueId;    private Long questionConId;    private String selected;// 学员答题记录    public StudentAnswerConEntity() {}    public StudentAnswerConEntity(Long studentAnswerQueId, Long questionConId) {        this.studentAnswerQueId = studentAnswerQueId;        this.questionConId = questionConId;    }    public Long getId() {        return id;    }    public void setId(Long id) {        this.id = id;    }    public Long getQuestionConId() {        return questionConId;    }    public void setQuestionConId(Long questionConId) {        this.questionConId = questionConId;    }    public Long getStudentAnswerQueId() {        return studentAnswerQueId;    }    public void setStudentAnswerQueId(Long studentAnswerQueId) {        this.studentAnswerQueId = studentAnswerQueId;    }    public String getSelected() {        return selected;    }    public void setSelected(String selected) {        this.selected = selected;    }}