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JPA

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  • 查询语言:Query Language
    • 条件表达式:where+having+on
      • 输入参数:支持位置参数 ?1,和命名参数 :userName,但这两者不能混用
      • 条件组合:属性导航:user.userName,一元运算 + -,逻辑操作 NOT AND OR,
        比较Comparison:= > >= < <= <>
        区间Between:[NOT] BETWEEN,支持数字、字符串、日期
        集合In:[NOT] IN,f in (‘a‘, ‘b‘) 等价于 f=‘a‘ or f=‘b‘
        相似Like:[NOT] LIKE,支持单个字符_、多个字符%、转义字符\_
        空值Null:IS [NOT] NULL,
        空集合:IS [NOT] EMPTY,select o from Order o where o.lineItems is empty,
        集合成员:[NOT] MEMBER OF,select p from Person p where ‘Joe‘ member of p.nicknames;
        存在性Exist:[NOT] EXISTS,select emp from Employee emp where exists ( select spouseEmp from Employee spouseEmp where spouseEmp = emp.spouse );//spouse配偶
        全部或任意:All+Any+Some,select emp from Employee where emp.salary > All { select m.salary from Manager m where m.department=emp.department };//部门高新员工
        子查询Subquery:select goodCustomer from Customer goodCustomer where goodCustomer.balanceOwed < ( select avg(c.balanceOwed)/2.0 from Customer c );//优质客户
      • 原生标准操作
        字符串:concat,substr,trim,lower,
        算术:abs,sqrt,mod,size,index(select w.name from Course c join c.studentsWaitlist w where c.name=‘Calculus‘ and index(w)=0;)
        聚合:count,max,min,avg,sum,distinct
        日期:current_date,current_time,current_timestamp
        过程调用:select c from Customer c where function( ‘hasGoodCredit‘, c.balance, c.creditLimit );
        分支语句:update Employee e set e.salary = 
        case e.rating when 1 then e.salary*1.1
                              when 2 then e.salary*1.05
                              else e.salary*1.01
        end
        类型判断:select e from Employee e where type(e) in ( Exempt, Contractor )
    • 分组和结果限定
      select c.status, avg(c.filledOrderCount), count(c) from Customer c group by c.status having c.status in ( 1, 2 );//统计状态1和2的客户信息
      select c, count(o) from Customer c Join c.orders o group by c having count(o) >= 5;//查询订单数大于等于5的客户
    • 排序
      select o from Customer c JOIN c.orders o JOIN c.address a where a.state=‘CA‘ order by o.quantity DESC, o.totalcost;//总量倒序,花费升序
    • 批量更新和删除
      delete from Customer c where c.status=‘inactive‘ and c.orders is empty;//删除未激活且没有订单的用户
      update Employee e set e.address.building=22 where e.address.building=14 and e.project=‘Java EE‘;//修改Java EE项目组成员的地址
  • 查询条件:Criteria,标准条件
    • CriteriaBuilder,@PersistenceUnit EntityManagerFactory.getCriteriaBuilder(); 或 @PersistenceContext EntityManager.getCriteriaBuilder();
      CriteriaQuery<T> createQuery(Class<T> resultClass);//创建查询,返回结果类型为resultClass
      CriteriaQuery<Tuple> createTupleQuery();//创建查询,返回元组类型,Tuple包含多个TupleElements
      CriteriaUpdate<T> createCriteriaUpdate(Class<T> targetEntity);//创建对targetEntity的批量修改操作
      CriteriaDelete<T> createCriteriaDelete(Class<T> targetEntity);//创建对targetEntity的批量删除操作
      CompoundSelection<Tuple> tuple(Selection<?>... selections);//创建tupe-valued查询
      CompoundSelection<Object[]> array(Selection<?>... selections);//创建array-valued查询
      Order asc(Expression<?> x);//创建表达式值的升序,desc为降序
      Expression<Double> avg(Expression<N> x);//计算平均值,还有count[Distinct],sum,max+min(数字),greatest+least(字符串、日期等),
      Predicate exists(Subquery<?> subquery);//判断子查询是否存在,还有all,some,any,isTrue,isFalse,is[Not]Null
      Predicate and(Expression<Boolean> x, Expression<Boolean> y);//逻辑与,还有or,not
      Predicate or(Predicate... restrictions);//多个条件或,还有与and
      Predicate conjunction();//条件与,没有时返回true;还有disjunction,条件或,没有时返回false;
      Predicate equal(Expression<?> x, Expression<?> y);//判断是否相等,还有greaterThan[OrEqualTo](Comparable),between,gt+ge+lt+le(Number)
      Predicate notEqual(Expression<?> x, Object value);//判断是否不等,还有lessThan[OrEqualTo],like+notLike
      Expression<Number> sum(Expression<?> x, N y);//算术运算,还有neg+abs+prod积+diff差+quot商+mod模+sqrt平方根+concat+substring+trim+upper+length+locate
      Expression<Long> toLong(Expression<?> x);//类型转换,还有Integer+Float+Double+BigDecimal+BigInteger+String
      Expression<T> literal(T value);//转换常量值,
      Predicate is[Not]Empty(Expression<c> collection);//测试集合非空,还有size+is[Not]Member,q.where(cb.isEmpty(order.get("lineItems"))); => where order.lineItems is empty
      Expression<Collection<V>> values(M map);//从map的values()创建集合条件,还有keys
      Expression<java.sql.Date> currentDate();//当前日期,还有java.sql.Time=currentTime,java.sql.Timestamp=currentTimestamp
      In<T> in(Expression<T> expression);//q.having( cb.in( customer.get("status").value(1).value(2) ) ); => having c.status in ( 1,2 )
    • CriteriaQuery -> AbstractQuery
      Root<X> from(Class<X> entityClass);//获得查询根,或与已有根计算笛卡尔积
      AbstractQuery<T> where(Predicate... restrictions);//限定条件(替换之间的条件)
      AbstractQuery<T> groupBy(Expression<?>... grouping);//分组,还有having+orderBy
      CriteriaQuery<T> select(Selection<?> selection);//设置选择结果
      CriteriaQuery<T> multiselect(Selection<?>... selections);//多个选择结果
      执行复杂条件查询
      @PersistenceContext EntityManager em;
      TypedQuery<T> query = em.createQuery(CriteriaQuery<T> cq);//创建查询对象
      query.setFirstResult().setMaxResults().getResultList();//获得查询结果
    • CriteriaUpdate+CriteriaDelete,有from+where
      CriteriaUpdate<T> set(Path attribute, X value);//更新属性

      update customer c set c.status=‘outstanding‘ where c.balance<1000;
      CriteriaUpdaate<Customer> q=cb.createCriteriaUpdate(Customer.class);
      Root<Customer> c=q.from(Customer.class);
      q.set(c.get("status"), "outstanding")
      .where( cb.lt(c.get("balance"), 1000) );
    • Root实体根+Join表连接 -> From查询 -> Path路径+Predicate与或 -> Expression表达式 -> Selection选择返回值
      Selection alias(String alias);//设置别名
      Predicate isNull();//是否空,还有isNotNull+
      Predicate in(Object... values);//集合元素,
      Path<Y> get(String attributeName);//获取路径
      Join join(String attributeName, JoinType type);//链接属性表,还有joinCollection,joinSet,joinList(t.index()限定多个对象的个数),joinMap(t.key()限定对象映射的key)
      Join on(Predicate... restrictions);//表链接
    • 查询样例,最好先组织SQL和JPQL语句,然后再翻译为对象方法调用
      • 获取全部或限定条件,select c from customer c where c.name="Jack";
        CriteriaQuery<Customer> q = CriteriaBuilder.createQuery(Customer.class);//返回类型为Customer
        Root<Customer> customer = q.from(Customer.class);//查询表Customer
        q.select(customer);//查询整个Customer对象
        q.where(cb.equal( customer.get("name"), ‘Jack‘));//限定name="Jack"的对象
      • 连接统计,select s.name, count(p) from Supplier s left join s.products on p.status=‘inStock‘ group by s.name;
        CriteriaQuery<Tuple> q = cb.createTupleQuery();//配合后面的multiselect
        Root<Supplier> s = q.from(Supplier.class);//
        Join<Supplier, Product> p = s.join("products", JoinType.LEFT);//连接产品表
        p.on(cb.equal(p.get("status"), "inStock"));//限定连接条件,s.join("products", JoinType.LEFT).on(cb.equal(p.get("status"), "inStock"));
        q.groupBy( s.get("name") );
        q.multiselect( s.get("name"), cb.count(p) );//等价于q.select(cb.tuple(s.get("name"), cb.count(p)));,还有cb.array,cb.construct(Type.class, ... args)
      • 深度获取fetch join,select d from Department d left join fetch d.employees where d.deptno=1;
        CriteriaQuery<Department> q = cb.createQuery(Department.class);
        Root<Department> d = q.from(Department.class);
        d.fetch("employees", JoinType.LEFT);//查询结果中d.employees有值
        q.where( cb.equal(d.get("deptno"), 1) );
        q.select(d);
      • 路径导航,select p.vendor from Employee e join e.contactInfo.phones p where e.contactInfo.address.zipcode="95054";
        CriteriaQuery<Vendor> q = cb.createQuery<Vendor.class>;//返回结果为Vendor
        Root<Employee> e = q.from(Employee.class);//从Employee开始查询
        Join<ContactInfo, Phone> phone = e.join("contactInfo").join("phones");//连接多张表
        q.where( cb.equal(e.get("contactInfo").get("address").get("zipcode"), "95054") );
        q.select( phone.get("vendor") );
      • 类型转换,select b.ISBN from Order o join treat(o.product AS Book) b;
        CriteriaQuery<String> q = cb.createQuery(String.class);
        Root<Order> order = q.from(Order.class);
        Join<Order, Book> book = cb.treat( order.join("product"), Book.class);
        q.select( book.get("isbn") );
      • 分支查询,
        select e.name ,
        case when e.rating=1 then e.salary*1.1
                when e.rating=2 then e.salary*1.2
                else e.salary&1.01
        from Employee e where e.department.name=‘Engineering‘;
        CriteriaQuery<Tuple> q=cb.createTupleQuery();
        Root<Employee> e=q.from(Employee.class);
        q.where( cb.equal(e.get("department").get("name"), "Engineering") );
        q.multiselect( e.get("name"), cb.selectCase()
                                                             .when(cb.equal(e.get("rating"), 1), cb.prod(e.get("salary"), 1.1))
                                                             .when(cb.equal(e.get("rating"), 2), prod(e.get("salary"), 1.2))//这里需要常量的话调用cb.literal("value")
                                                             .otherWise(cb.prod(e.get("salary"), 1.01)) );
      • 参数
        select c from Customer c where c.status = :stat;
        CriteriaQuery<Customer> q=cb.createQuery(Customer.class);
        Root<Customer> c=q.from(Customer.class);
        ParameterExpression<Integer> param=cb.parameter(Integer.class, "stat");
        q.select(c).where(cb.equal(c.get("status"), param));
      • 子查询,select goodCustomer from Customer goodCustomer where goodCustomer.balanceOwed < ( select avg(c.balanceOwed) from Customer c );
        CriteriaQuery<Customer> q=cb.createQuery(Customer.class);
        Root<Customer> goodCustomer=q.from(Customer.class);
        Subquery<Double> sq=q.subquery(Double.class);//子查询返回double值
        Root<Customer> customer=sq.from(Customer.class);
        q.where(cb.lt(goodCustomer.get("balanceOwed"), sq.select(cb.avg(customer.get("balanceOwed")))));//goodCustomer.balanceOwed < avg(customer.balanceOwed)
        q.select(goodCustomer);

        select emp from Employee emp where emp.salary > all ( select m.salary from Manager m where m.department=emp.department );
        CriteriaQuery<Employee> q=cb.createQuery(Employee.class);
        Root<Employee> emp=q.from(Employee.class);
        Subquery<BigDecimal> sq=q.subquery(BigDecimal.class);
        Root<Manager> manager=sq.from(Manager.class);
        sq.select(manager.get("salary"));
        sq.where(cb.equals(manager.get("department"), emp.get("department")));
        q.select(emp).where(cb.gt(emp.get("salary"), cb.all(sq)));
  • EntityManager
    • 获得EntityManager
      @PersistenceContext EntityManager em;
      @PersistenceUnit EntityManagerFactory emf; emf.createEntityManager()//
      javax.persistence.Persistence.createEntityManagerFactory("order");//从persistence.xml文件读取unit配置
  • 统计接口及实现:
    调用优先级Criteria API > Java Persistence Query Language > SQL
    有些统计语句可能是在很复杂只好执行原始的SQL语句了(sql条件需在可控范围内,最好检查一下参数安全性),但前两种在适当的时候还是应当多用的(防SQL注入)
    public class TongjiReposityImpl implements TongjiRepository {
        @PersistenceContext private EntityManager entityManager;
        @Override
        public CriteriaBuilder builder() {//Criteria API
            return entityManager.getCriteriaBuilder();
        }
        @Override
        public long count(CriteriaQuery<Long> query) {
            TypedQuery<Long> typedQuery = entityManager.createQuery(query);
            return typedQuery.getSingleResult();
        }
        @Override
        public Object[] sums(CriteriaQuery<Tuple> query) {
            List<Tuple> list = list(query, 0, 0);
            return list!=null && list.size()>0 ? list.get(0).toArray() : null;
        }
        @Override
        public List<Tuple> list(CriteriaQuery<Tuple> query, int firstResult, int maxResults) {
            TypedQuery<Tuple> typedQuery = entityManager.createQuery(query);
            typedQuery.setFirstResult(firstResult);
            if(maxResults>0) typedQuery.setMaxResults(maxResults);
            return typedQuery.getResultList();
        }
        @Override
        public int count(String jpql, Object... args) {//Java Persistence Query Language
            Query query = entityManager.createQuery(jpql);
            if(args!=null && args.length>0) {
                for(int i=0; i<args.length; i++) {
                    query.setParameter(i+1, args[i]);
                }
            }
            return ((Number)query.getSingleResult()).intValue();
        }
        @Override
        public Object[] sums(String jpql, Object... args) {
            List<?> list = list(jpql, args);
            if(list!=null && list.size()>0) {
                Object obj = list.get(0);
                if(obj instanceof Object[]) {
                    return (Object[])obj;
                }else {
                    return new Object[] {obj};
                }
            }
            return null;
        }
        @Override
        public List<?> list(String jpql, Object... args) {
            Query query = entityManager.createQuery(jpql);
            if(args!=null && args.length>0) {
                for(int i=0; i<args.length; i++) {
                    query.setParameter(i+1, args[i]);
                }
            }
            return query.getResultList();
        }
        @Override
        public int count(String sql) {//SQL
            Query query = entityManager.createNativeQuery(sql);
            return ((Number)query.getSingleResult()).intValue();
        }
        @Override
        public Object[] sums(String sql) {
            List<?> list = list(sql);
            if(list!=null && list.size()>0) {
                Object obj = list.get(0);
                if(obj instanceof Object[]) {
                    return (Object[])obj;
                }else {
                    return new Object[] {obj};
                }
            }
            return null;
        }
        @Override
        public List<?> list(String sql) {
            Query query = entityManager.createNativeQuery(sql);
            return query.getResultList();
        }
    }  
  • sql辅助生成工具类
    /**
     * select column from table where condition group by column having condition order by column limit from,length
     */
    public class SqlBuilder {
        private String select;
        private String from;
        private StringBuilder where = new StringBuilder();
        private String groupBy;
        private String having;
        private String orderBy;
        private String limit;
        
        public static SqlBuilder builder() {
            return new SqlBuilder();
        }
        
        /**
         * @param select
         * <li>*
         * <li>column1,column2,...
         * <li>count(column1),sum(column2),avg(column3),...
         * <li>user.id,user.name,account.amount,...
         */
        public SqlBuilder select(String select) {
            this.select = select;
            return this;
        }
        
        /**
         * @param from
         * <li>ts_user
         * <li>ts_user u left join ts_account a on u.ts_user_id = a.ts_user_id
         * <li>jpql: TsUser user left join user.tsAccount account
         */
        public SqlBuilder from(String from) {
            this.from = from;
            return this;
        }
        
        /**
         * @param where
         * <li>null, to reset where
         * <li>name like ‘%Jack%‘
         * <li>id in (1,2,3)
         * <li>exists (select a.id from acount a where a.user_id=user.id)
         * <li>name is empty
         */
        public SqlBuilder where(String where) {
            if(StringUtils.isEmpty(where)) {
                this.where.setLength(0);
            }else {
                this.where.append(" and " + where);
            }
            return this;
        }
        
        /**
         * @param columnOperator
         * <li>column1 >=
         * <li>column2 !=
         */
        public SqlBuilder where(String columnOperator, Object value) {
            if(!StringUtils.isEmpty(value)) {
                where.append(" and " + columnOperator + " ‘" + sqlParam(value.toString()) + "‘");
            }
            return this;
        }
        
        public SqlBuilder groupBy(String groupBy) {
            this.groupBy = groupBy;
            return this;
        }
        
        public SqlBuilder having(String having) {
            this.having = having;
            return this;
        }
        
        public SqlBuilder orderBy(String orderBy) {
            this.orderBy = orderBy;
            return this;
        }
        
        /**
         * @param limit
         * <li>limit 0,10
         */
        public SqlBuilder limit(String limit) {
            this.limit = limit;
            return this;
        }
        
        public SqlBuilder eq(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                where.append(" and " + column + " = ‘" + sqlParam(value.toString()) + "‘");
            }
            return this;
        }
        
        public SqlBuilder ne(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                where.append(" and " + column + " != ‘" + sqlParam(value.toString()) + "‘");
            }
            return this;
        }
        
        public SqlBuilder like(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                where.append(" and " + column + " like ‘%" + sqlParam(value.toString()) + "%‘");
            }
            return this;
        }
        
        public SqlBuilder notLike(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                where.append(" and " + column + " not like ‘%" + sqlParam(value.toString()) + "%‘");
            }
            return this;
        }
        
        public SqlBuilder in(String column, Collection<?> value) {
            if(!CollectionUtils.isEmpty(value)) {
                where.append(" and " + column + " in (" + StringUtils.collectionToDelimitedString(value, ",""‘""‘") + ")");
            }
            return this;
        }
        
        public SqlBuilder notIn(String column, Collection<?> value) {
            if(!CollectionUtils.isEmpty(value)) {
                where.append(" and " + column + " not in (" + StringUtils.collectionToDelimitedString(value, ",""‘""‘") + ")");
            }
            return this;
        }
        
        public SqlBuilder gt(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                where.append(" and " + column + " > ‘" + sqlParam(value.toString()) + "‘");
            }
            return this;
        }
        
        public SqlBuilder gte(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                where.append(" and " + column + " >= ‘" + sqlParam(value.toString()) + "‘");
            }
            return this;
        }
        
        public SqlBuilder lt(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                where.append(" and " + column + " < ‘" + sqlParam(value.toString()) + "‘");
            }
            return this;
        }
        
        public SqlBuilder lte(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                where.append(" and " + column + " <= ‘" + sqlParam(value.toString()) + "‘");
            }
            return this;
        }
        
        public SqlBuilder between(String column, Object from, Object to) {
            if(StringUtils.isEmpty(from) && StringUtils.isEmpty(to)) return this;
            if(!StringUtils.isEmpty(from)) where.append(" and " + column + " >= ‘" + sqlParam(from.toString()) + "‘");
            else if(!StringUtils.isEmpty(to)) where.append(" and " + column + " <= ‘" + sqlParam(to.toString()) + "‘");
            else where.append(" and " + column + " between ‘" + sqlParam(from.toString()) + "‘ and ‘" + sqlParam(to.toString()) + "‘");
            return this;
        }
        
        public String sql() {
            if(select == null || from == null//必须得有selece和from部分
                throw new RuntimeException("sql must contain select + from parts.");
            
            StringBuilder sql = new StringBuilder("select " + select+" from "+from);
            if(where.length() > 4) sql.append(" where " + where.substring(5));
            if(groupBy != null) sql.append(" group by " + groupBy);
            if(having != null) sql.append(" having " + having);
            if(orderBy != null) sql.append(" order by " + orderBy);
            if(limit != null) sql.append(" limit " + limit);
            return sql.toString();
        }
        //过滤掉引号‘",逗号,分号;注释号--等sql敏感符号
        public static String sqlParam(String sqlParam) {
            return sqlParam.replaceAll("([‘;]+|(--)+)""");
        }
    }
  • jpql辅助工具类,与SqlBuilder类似
    public class JpqlBuilder {
        private String select;
        private String from;
        private StringBuilder where = new StringBuilder();
        private List<Object> args = new ArrayList<Object>();
        private String groupBy;
        private String having;
        private String orderBy;
        private String limit;
        
        public static JpqlBuilder builder() {
            return new JpqlBuilder();
        }
        
        /**
         * @param select
         * <li>*
         * <li>user.id,user.name,account.amount,...
         */
        public JpqlBuilder select(String select) {
            this.select = select;
            return this;
        }
        
        /**
         * @param from
         * <li>jpql: TsUser user left join user.tsAccount account
         */
        public JpqlBuilder from(String from) {
            this.from = from;
            return this;
        }
        
        /**
         * @param where
         * <li>null, to reset where
         * <li>name like ‘%Jack%‘
         */
        public JpqlBuilder where(String where) {
            if(StringUtils.isEmpty(where)) {
                this.where.setLength(0);
                args.clear();
            }else {
                this.where.append(" and " + where);
            }
            return this;
        }
        
        /**
         * @param columnOperator
         * <li>column1 >=
         * <li>column2 !=
         */
        public JpqlBuilder where(String columnOperator, Object value) {
            if(!StringUtils.isEmpty(value)) {
                args.add(value);
                where.append(" and " + columnOperator + " ?" + args.size());
            }
            return this;
        }
        
        public JpqlBuilder groupBy(String groupBy) {
            this.groupBy = groupBy;
            return this;
        }
        
        public JpqlBuilder having(String having) {
            this.having = having;
            return this;
        }
        
        public JpqlBuilder orderBy(String orderBy) {
            this.orderBy = orderBy;
            return this;
        }
        
        /**
         * @param limit
         * <li>limit 0,10
         */
        public JpqlBuilder limit(String limit) {
            this.limit = limit;
            return this;
        }
        
        public JpqlBuilder eq(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                args.add(value);
                where.append(" and " + column + " = ?" + args.size());
            }
            return this;
        }
        
        public JpqlBuilder ne(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                args.add(value);
                where.append(" and " + column + " != ?" + args.size());
            }
            return this;
        }
        
        public JpqlBuilder like(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                args.add(value);
                where.append(" and " + column + " like ?" + args.size());
            }
            return this;
        }
        
        public JpqlBuilder notLike(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                args.add(value);
                where.append(" and " + column + " not like ?" + args.size());
            }
            return this;
        }
        
        public JpqlBuilder in(String column, Collection<?> value) {
            if(!CollectionUtils.isEmpty(value)) {
                where.append(" and " + column + " in (");
                boolean first = true;
                for(Object obj : value) {
                    args.add(obj);
                    if(first) {
                        first = false;
                        where.append("?"+args.size());
                    }else {
                        where.append(" , ?"+args.size());
                    }
                }
                where.append(")");
            }
            return this;
        }
        
        public JpqlBuilder notIn(String column, Collection<?> value) {
            if(!CollectionUtils.isEmpty(value)) {
                where.append(" and " + column + " not in (");
                boolean first = true;
                for(Object obj : value) {
                    args.add(obj);
                    if(first) {
                        first = false;
                        where.append("?"+args.size());
                    }else {
                        where.append(" , ?"+args.size());
                    }
                }
                where.append(")");
            }
            return this;
        }
        
        public JpqlBuilder gt(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                args.add(value);
                where.append(" and " + column + " > ?" + args.size());
            }
            return this;
        }
        
        public JpqlBuilder gte(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                args.add(value);
                where.append(" and " + column + " >= ?" + args.size());
            }
            return this;
        }
        
        public JpqlBuilder lt(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                args.add(value);
                where.append(" and " + column + " < ?" + args.size());
            }
            return this;
        }
        
        public JpqlBuilder lte(String column, Object value) {
            if(!StringUtils.isEmpty(value)) {
                args.add(value);
                where.append(" and " + column + " <= ?" + args.size());
            }
            return this;
        }
        
        public JpqlBuilder between(String column, Object from, Object to) {
            if(StringUtils.isEmpty(from) && StringUtils.isEmpty(to)) return this;
            if(!StringUtils.isEmpty(from)) {
                args.add(from);
                where.append(" and " + column + " >= ?" + args.size());
            }else if(!StringUtils.isEmpty(to)) {
                args.add(to);
                where.append(" and " + column + " <= ?" + args.size());
            }else {
                args.add(from);
                args.add(to);
                where.append(" and " + column + " between ?" + (args.size()-1) + " and ?" + args.size());
            }
            return this;
        }
        
        public String jpql() {
            if(select == null || from == null//必须得有selece和from部分
                throw new RuntimeException("sql must contain select + from parts.");
            
            StringBuilder sql = new StringBuilder("select " + select+" from "+from);
            if(where.length() > 4) sql.append(" where " + where.substring(5));
            if(groupBy != null) sql.append(" group by " + groupBy);
            if(having != null) sql.append(" having " + having);
            if(orderBy != null) sql.append(" order by " + orderBy);
            if(limit != null) sql.append(" limit " + limit);
            return sql.toString();
        }
        
        public Object[] args() {
            return args.toArray();
        }
    }  




JPA

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原文地址:http://www.cnblogs.com/xingqi/p/3929386.html

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