反射2-spring boot jpa 注入model即实现查询

spring boot jpa 
使用方法：
将对应的model类注入即可
// fixed parameter type
    private Specification<TargetModel> findByConditionSpecification(TargetModel formalParameter) {
        return new Specification<TargetModel>() {

            // fixed parameter type
            @Override
            public Predicate toPredicate(Root<TargetModel> root, CriteriaQuery<?> query,
                    CriteriaBuilder criteriaBuilder) {
                List<Predicate> predicates = new ArrayList<Predicate>();
                // fixed parameter type
                Class clsEmployeeBase = TargetServiceImpl.class;

                Method[] methods = clsEmployeeBase.getDeclaredMethods();
                try {
                    for (Method method : methods) {
                        if (method.getName().equals("findByConditionSpecification")) {
                            Class clsEmployee = formalParameter.getClass();
                            Field[] fields = clsEmployee.getDeclaredFields();
                            for (Field field : fields) {
                                field.setAccessible(true);
                                if (!"serialVersionUID".equals(field.getName()) && field.get(formalParameter) != null) {
                                    switch (field.getName()) {
                                    case "id": {
                                        // TODO fixed parameter,formal patameter primary key
                                        TargetIdentity id = (TargetIdentity) field.get(formalParameter);
                                        Field[] idFields = id.getClass().getDeclaredFields();
                                        for (Field idField : idFields) {
                                            idField.setAccessible(true);
                                            if (!"serialVersionUID".equals(idField.getName())
                                                    && idField.get(id) != null) {

                                                String paramType = String.valueOf(idField.getType()).split(" ")[1];
                                                switch (paramType) {
                                                case "java.lang.String": {
                                                    String[] strs = String.valueOf(idField.get(id)).split(",");
                                                    Expression<String> express = root.get("id").get(idField.getName());
                                                    CriteriaBuilder.In<String> in = criteriaBuilder.in(express);
                                                    Arrays.asList(strs).forEach(n -> {
                                                        in.value(n);
                                                    });
                                                    predicates.add(in);
                                                    break;
                                                }
                                                case "java.util.Date": {
                                                    if (idField.getName().contains("start")) {
                                                        Expression<Date> express = root.get("id")
                                                                .get(idField.getName());
                                                        predicates.add(criteriaBuilder.greaterThanOrEqualTo(express,
                                                                (Date) (idField.get(id))));
                                                        break;
                                                    }

                                                    if (idField.getName().contains("end")) {
                                                        Expression<Date> express = root.get("id")
                                                                .get(idField.getName());
                                                        predicates.add(criteriaBuilder.lessThanOrEqualTo(express,
                                                                (Date) (idField.get(id))));
                                                        break;
                                                    }

                                                }

                                                default: {
                                                    Expression express = root.get("id").get(idField.getName());
                                                    predicates.add(criteriaBuilder.equal(express, idField.get(id)));
                                                    break;

                                                }
                                                }

                                            }
                                        }

                                        break;
                                    }
                                    // 非联合主键
                                    default: {
                                        String paramType = String.valueOf(field.getType()).split(" ")[1];
                                        switch (paramType) {
                                        case "java.lang.String": {
                                            String[] strs = String.valueOf(field.get(formalParameter)).split(",");
                                            Expression<String> express = root.get(field.getName());
                                            CriteriaBuilder.In<String> in = criteriaBuilder.in(express);
                                            Arrays.asList(strs).forEach(n -> {
                                                in.value(n);
                                            });
                                            predicates.add(in);
                                            break;
                                        }
                                        case "java.util.Date": {
                                            if (field.getName().contains("start")) {
                                                Expression<Date> express = root.get(field.getName());
                                                predicates.add(criteriaBuilder.greaterThanOrEqualTo(express,
                                                        (Date) (field.get(formalParameter))));
                                                break;
                                            }

                                            if (field.getName().contains("end")) {
                                                Expression<Date> express = root.get(field.getName());
                                                predicates.add(criteriaBuilder.lessThanOrEqualTo(express,
                                                        (Date) (field.get(formalParameter))));
                                                break;
                                            }

                                        }

                                        default: {
                                            Expression express = root.get(field.getName());
                                            predicates.add(criteriaBuilder.equal(express, field.get(formalParameter)));
                                            break;

                                        }
                                        }
                                        break;
                                    }
                                    }

                                }

                            }
                        }
                    }

                } catch (Exception e) {
                    // TODO: handle exception
                }
                query.where(predicates.toArray(new Predicate[predicates.size()]));
                return query.getRestriction();
            }
        };

    }