在 SQL 语句中，支持通过 where 语句实现各种简单、复杂的条件查询。JPA 中的 JPQL 语句也允许定义各种查询条件，根据条件筛选数据。
（1）配置 persistence.xml，如下：
<persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.0"> <persistence-unit name="openJPA2" transaction-type="RESOURCE_LOCAL"> <!-- JPA提供者 --> <provider>org.apache.openjpa.persistence.PersistenceProviderImpl</provider> <!-- 声明实体类 --> <class>com.hxstrive.openjpa.entity2.User</class> <!-- 配置JPA数据库属性 --> <properties> <property name="openjpa.ConnectionURL" value="jdbc:mysql://localhost:3306/openjpa_learn?useSSL=false& serverTimezone=UTC&useUnicode=true&characterEncoding=UTF-8"/> <property name="openjpa.ConnectionDriverName" value="com.mysql.jdbc.Driver"/> <property name="openjpa.ConnectionUserName" value="root"/> <property name="openjpa.ConnectionPassword" value="aaaaaa"/> <property name="openjpa.Log" value="SQL=TRACE"/> <!-- 自动生成表 --> <property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(ForeignKeys=true)"/> <!-- 不使用加载时强化和编译时强化，使用运行时Unenhanced（不能发挥OpenJPA的最大效能，所以也不推荐） --> <property name="openjpa.ClassLoadEnhancement" value="false"/> <property name="openjpa.DynamicEnhancementAgent" value="false"/> <property name="openjpa.RuntimeUnenhancedClasses" value="supported"/> </properties> </persistence-unit> </persistence>
（2）用户表实体映射，代码如下：
@Data
@Entity
@Table
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
@Column
private String name;
@Column
private Integer age;
@Column
private Float salary;
}在介绍过滤器之前，我们介绍一下执行 JPQL 语句的模版方法。代码如下：
public class JPQLDemo5 {
/** 持久化单元名称 */
private static final String PERSISTENCE_NAME = "openJPA2";
private static void query(EntityManager em, String sql) {
TypedQuery<User> query = em.createQuery(sql, User.class);
List<User> userList = query.getResultList();
for (User user : userList) {
System.out.println(user);
}
}
public static void main(String[] args) {
EntityManagerFactory factory = Persistence.createEntityManagerFactory(
PERSISTENCE_NAME, System.getProperties());
EntityManager em = factory.createEntityManager();
// 大于、小于等于
// query(em, "你的JPQL语句");
em.close();
factory.close();
System.out.println("finished.");
}
}检索 age 等于 80 的用户信息，代码如下：
query(em, "select t from User t where t.age=80");
输出如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0 WHERE (t0.age = ?) [params=?]
User{id=2, name='用户-1', age=80, salary=7253.2427}
User{id=8, name='用户-7', age=80, salary=3047.556}检索 age 不等于 80 的用户信息，代码如下：
query(em, "select t from User t where t.age <> 80");
输出如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0 WHERE (t0.age <> ?) [params=?]
User{id=1, name='用户-0', age=56, salary=7251.132}
User{id=3, name='用户-2', age=44, salary=5855.36}
User{id=4, name='用户-3', age=10, salary=4105.1895}检索 age 大于 20 ，且小于等于 60 的用户信息，代码如下：
query(em, "select t from User t where t.age > 20 and t.age <= 60");
输出如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0 WHERE (t0.age > ? AND t0.age <= ?) [params=?, ?]
User{id=1, name='用户-0', age=56, salary=7251.132}
User{id=3, name='用户-2', age=44, salary=5855.36}
User{id=5, name='用户-4', age=53, salary=2927.5222}
User{id=10, name='用户-9', age=26, salary=6327.472}检索 age 大于 20 ，且小于等于 60 的用户信息，代码如下：
query(em, "select t from User t where t.age between 20 and 60");
输出如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0 WHERE (t0.age >= ? AND t0.age <= ?) [params=?, ?]
User{id=1, name='用户-0', age=56, salary=7251.132}
User{id=3, name='用户-2', age=44, salary=5855.36}
User{id=5, name='用户-4', age=53, salary=2927.5222}
User{id=10, name='用户-9', age=26, salary=6327.472}检索 name 包含 "8" 字符串的用户信息，代码如下：
query(em, "select t from User t where t.name like '%8%'");
输出如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0 WHERE (t0.name LIKE ? ESCAPE '\\') [params=?]
User{id=9, name='用户-8', age=79, salary=7199.551}检索 id 等于 1、2 或 3 的用户信息，代码如下：
query(em, "select t from User t where t.id in(1,2,3)");
输出如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0 WHERE ((t0.id = ? OR t0.id = ? OR t0.id = ?) AND t0.id IS NOT NULL) [params=?, ?, ?]
User{id=1, name='用户-0', age=56, salary=7251.132}
User{id=2, name='用户-1', age=80, salary=7253.2427}
User{id=3, name='用户-2', age=44, salary=5855.36}检索 id 不等于 1、2 和 3 的用户信息，代码如下：
query(em, "select t from User t where t.id not in(1,2,3)");
输出如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0 WHERE (NOT (t0.id = ? OR t0.id = ? OR t0.id = ?) AND t0.id IS NOT NULL) [params=?, ?, ?]
User{id=4, name='用户-3', age=10, salary=4105.1895}
User{id=5, name='用户-4', age=53, salary=2927.5222}
User{id=6, name='用户-5', age=73, salary=8892.097}
User{id=7, name='用户-6', age=77, salary=5494.797}AND运算符只有当满足所有给出的条件时，才能够成功获取到相应数据。
例如：检索 age 大于 50，且小于 80 的用户数据
query(em, "select t from User t where t.age>50 and t.age<80");
输出如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0 WHERE (t0.age > ? AND t0.age < ?) [params=?, ?]
User{id=1, name='用户-0', age=56, salary=7251.132}
User{id=5, name='用户-4', age=53, salary=2927.5222}
User{id=6, name='用户-5', age=73, salary=8892.097}
User{id=7, name='用户-6', age=77, salary=5494.797}
User{id=9, name='用户-8', age=79, salary=7199.551}OR 运算符使用方法其实和 AND 运算符很像，不同的是，OR 运算符只需要满足多个条件中的任意一个条件，即可成功获取到相应数据。
例如：检索 age 小于 50，或 age 大于80 的用户数据
query(em, "select t from User t where t.age>80 or t.age<50");
输出如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0 WHERE (t0.age > ? OR t0.age < ?) [params=?, ?]
User{id=3, name='用户-2', age=44, salary=5855.36}
User{id=4, name='用户-3', age=10, salary=4105.1895}
User{id=10, name='用户-9', age=26, salary=6327.472}下面将演示 and 和 or 操作符的用法，代码如下：
query(em, "select t from User t where t.age>50 and (t.salary > 8000 or t.salary < 3000)");
输出如下：
SELECT t0.id, t0.age, t0.name, t0.salary FROM User t0 WHERE (t0.age > ? AND (t0.salary > ? OR t0.salary < ?)) [params=?, ?, ?]
User{id=5, name='用户-4', age=53, salary=2927.5222}
User{id=6, name='用户-5', age=73, salary=8892.097}
