处理QueryDSL中的可选参数

Question

我将QueryDSL与SpringData一起使用。我有表say,Employee并创建了实体类say,EmployeeEntity我编写了以下服务方法

public EmployeeEntity getEmployees(String firstName, String lastName)
{
    QEmployeeEntity employee = QEmployeeEntity.employeeEntity;
    BooleanExpression query = null;
    if(firstName != null)
    {
        query = employee.firstName.eq(firstName);
    }
    if(lastName != null)
    {
        query = query.and(employee.lastName.eq(lastName)); // NPException if firstName is null as query will be NULL
    }
    return empployeeDAO.findAll(query);
}

与上面一样，我注释了NPException。如何在使用Spring数据的QueryDSL中对可选参数使用QueryDSL？

Answer 1

BooleanBuilder可用作布尔表达式的动态生成器：

public EmployeeEntity getEmployees(String firstName, String lastName) {
    QEmployeeEntity employee = QEmployeeEntity.employeeEntity;
    BooleanBuilder where = new BooleanBuilder();
    if (firstName != null) {
        where.and(employee.firstName.eq(firstName));
    }
    if (lastName != null) {
        where.and(employee.lastName.eq(lastName));
    }
    return empployeeDAO.findAll(where);
}