JPA實現動態查詢

前言
之前使用jpa的時候一直感慨它的一些原來就有的方法很好用，一邊不是很習慣這種不是xml寫sql的方式，尤其在用習慣了mybatis之后，在使用jpa寫動態查詢的時候真的一頭霧水，直到發現了**Specification** 這個神奇的東西，使用下來覺得他和mybatis plus的條件構造器很像，而且可以實現動態查詢，特意記錄一下
代碼
JPA

List<Apply> findAll(Specification<Apply> specification);

service

public List<Apply> getAllDynamatic(Apply apply) {
Specification<Apply> queryCondition = new Specification<Apply>() {
@Override
public Predicate toPredicate(Root<Apply> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
List<Predicate> predicateList = new ArrayList<>();
// 根據傳遞的對象來進行條件的構造
if (apply.getId() != null) {
predicateList.add(criteriaBuilder.equal(root.get("id"), apply.getId()));
}
if (apply.getState() != null) {
predicateList.add(criteriaBuilder.equal(root.get("state"), apply.getState()));
}
if (apply.getAwardtype() != null) {
predicateList.add(criteriaBuilder.equal(root.get("awardtype"), apply.getAwardtype()));
}
if (apply.getStudentid() != null) {
predicateList.add(criteriaBuilder.equal(root.get("studentid"), apply.getStudentid()));
}
if (apply.getInfo() != null) {
predicateList.add(criteriaBuilder.equal(root.get("info"), apply.getInfo()));
}
if (apply.getName() != null) {
predicateList.add(criteriaBuilder.equal(root.get("name"), apply.getName()));
}
if (apply.getType() != null) {
predicateList.add(criteriaBuilder.equal(root.get("type"), apply.getType()));
}
if (apply.getTeacherid() != null) {
predicateList.add(criteriaBuilder.equal(root.get("teacherid"), apply.getTeacherid()));
}
if (apply.getTeacherstate() != null) {
predicateList.add(criteriaBuilder.equal(root.get("teacherstate"), apply.getTeacherstate()));
}
if (apply.getProcess() != null) {
predicateList.add(criteriaBuilder.equal(root.get("process"), apply.getProcess()));
}
if (apply.getProcess2() != null) {
predicateList.add(criteriaBuilder.equal(root.get("process2"), apply.getProcess2()));
}

return criteriaBuilder.and(predicateList.toArray(new Predicate[predicateList.size()]));
}
};
return applyRepos.findAll(queryCondition);
}

這樣就實現了jpa的動態查詢