JPA动态查询

CriteriaBuilder cb=entityManager.getCriteriaBuilder();
CriteriaQuery<T> query=cb.createQuery(clazz);
//clazz是你想要转换的类型，就是你的Entity.claa，如果你查的是count,就是Long.claa
Root<T> root=query.from(clazz);
query.select(root);//选取实体

Predicate predicate=cb.conjunction();//交集
predicate=cb.and(predicate,cb.equal(root.get("sex"),condition.get("sex")));

Predicate predicate=cb.disjunction();//并集
predicate=cb.or(predicate,cb.equal(root.get("sex"),condition.get("sex")));

JPA里面对类型控制比较严格，如下所示：

//比较大小
cb.gt(root.<Integer>get("degree"),(Integer) condition.get("degree"));

//like
cb.like(root.get("user").<String> get("nickName"),keyword)

//in 条件
root.get("tags").in(condition.get("tag"))

Java CriteriaBuilder.disjunction方法代碼示例

import javax.persistence.criteria.CriteriaBuilder; //導入方法依賴的package包/類
private Predicate getPredicateGlobalSearch(final Root<T> root,final CriteriaQuery<?> 
                     query, final CriteriaBuilder cb, Predicate predicate) {
    // check whether a global filter value exists
    final String globalFilterValue = input.getSearch().getValue();
    if (globalFilterValue != null && globalFilterValue.trim().length() > 0) {
        LOGGER.fine("filtre global: {"+ globalFilterValue+"}");

        Predicate matchOneColumnPredicate = cb.disjunction();
        // add a 'WHERE .. LIKE' clause on each searchable column
        for (final DatatableColumn column : input.getColumns()) {
            if (column.getSearchable()) {
                LOGGER.log(Level.FINE, "filtre global pour colonne: {}", column);
                final Expression<String> expression = 
                        DatatableHelper.getExpression(
                        root, column.getData(), String.class);

                matchOneColumnPredicate =cb.or(matchOneColumnPredicate,
                                              cb.like(cb.lower(expression), 
                                              getLikeFilterValue(globalFilterValue), 
                                              ESCAPE_CHAR));
            }
        }
        predicate = cb.and(predicate, matchOneColumnPredicate);
    }
    return predicate;
}