java - 在jpa中生成报告

Question

我正在学习 JPA，想知道如何使用下面的查询生成报告。

Query query = em
            .createQuery("SELECT t.firstName, t.lastName, t.salary FROM Teacher t");

    List results = query.getResultList();
    Object[] objects = results.toArray(new Object[results.size()]);
    for (Object object : objects) {
        System.out.println(object);// here I want to print firstName, lastName
    }

我知道 getResultList() 方法返回对象数组列表。但我想在这里打印 firstName、lastName 和 salary 。我怎样才能做到这一点？我不能简单地将 Object 转换为 String。

Answer 1

试试这个。

List<Object[]> list = query.getResultList();
for (int index = 0; index < list.size(); index++) {
    Object[] objArr = list.get(index); //this will return a row of your result into objArr
    for (int j = 0; j < 3; j++) {
        //here, you are now iterating through the columns in each row. Since your select query has 3 columns j <3 in the for loop
        System.out.println(objArr[j].toString());
    }
}