java中mongodb的查询及排序

转载自：http://www.zicheng.net/article/982042.htm

 Mongodb除了高性能外，还有完善的API进行各种查询操作，本教程中，我将为你演示一些通用的方法来实现mongodb的查询，包括组合查询，区间查询，like查询,in查询等方法。希望在阅读本文后能举一反三组合成更复杂的查询。

 

下面直接上代码，每个代码里有详细的注释，有疑问请留言。

001 public class MongoDbFind {
002     public static final int port = 27017;
003     public static final String host = "127.0.0.1";
004     /**
005      * 获取数据库对象
006      *
007      * @return
008      */
009     private MongoDatabase getDb() {
010         MongoClient mongo = new MongoClient(host, port);
011         MongoDatabase db = mongo.getDatabase("new_db");
012         return db;
013     }
014     /**
015      * 获取表（集合）
016      *
017      * @return
018      */
019     private MongoCollection getCollection() {
020         MongoDatabase db = getDb();
021         MongoCollection table = db.getCollection("user");
022         return table;
023     }
024     /**
025      * 查询出一条数据
026      */
027     @Test
028     public void findOne() {
029         MongoCollection table = getCollection();
030         BasicDBObject dbObject = new BasicDBObject();
031         //mongodb中按age字段倒序查询（-1是倒序，1是正序）
032         dbObject.put("age",-1);
033         FindIterable iterate = table.find().sort(dbObject).limit(1);
034         System.out.println(iterate.iterator().tryNext());
035     }
036     /**
037      * mongodb分页查询
038      *
039      * @param pageIndex 当前页码
040      */
041     private void findPage(int pageIndex) {
042         int pageSize = 3;
043         MongoCollection table = getCollection();
044         //mongodb分页查询出游标
045         MongoCursor cursor = table.find().limit(pageSize).skip((pageIndex - 1) * pageSize).iterator();
046         System.out.println("当前页：" + pageIndex);
047         while (cursor.hasNext()) {
048             System.out.println(cursor.next());
049         }
050     }
051     @Test
052     public void findPage() {
053         findPage(1);
054         findPage(2);
055     }
056     /**
057      * 等于查询
058      */
059     @Test
060     public void comparison() {
061         MongoCollection table = getCollection();
062         BasicDBObject dbObject = new BasicDBObject();
063         dbObject.put("age", 20);
064         //查询出年龄是20的记录
065         MongoCursor cursor = table.find(dbObject).iterator();
066         while (cursor.hasNext()) {
067             System.out.println(cursor.next());
068         }
069     }
070     /**
071      * 使用in包含查询
072      */
073     @Test
074     public void findIn() {
075         //定义一个数组存储in查询的条件值
076         List list = new ArrayList<>(4);
077         list.add(20);
078         list.add(28);
079         list.add(15);
080         list.add(13);
081         MongoCollection table = getCollection();
082         BasicDBObject dbObject = new BasicDBObject();
083         //这里使用BasicDBObject嵌套来并使用$in预定义名称来实现mongodb的in查询功能
084         dbObject.put("age", new BasicDBObject("$in", list));
085         MongoCursor cursor = table.find(dbObject).iterator();
086         while (cursor.hasNext()) {
087             System.out.println(cursor.next());
088         }
089     }
090     /**
091      * 大于小于区间查询
092      */
093     @Test
094     public void findGtLt()
095     {
096         MongoCollection table = getCollection();
097         BasicDBObject dbObject = new BasicDBObject();
098         //mongodb实现大于小于区间的查询，注意大于是$gt,小于是$lt
099         dbObject.put("age", new BasicDBObject("$gt", 15).append("$lt",25));
100         MongoCursor cursor = table.find(dbObject).iterator();
101         while (cursor.hasNext()) {
102             System.out.println(cursor.next());
103         }
104     }
105     /**
106      * 不等于查询
107      */
108     @Test
109     public void findNe()
110     {
111         MongoCollection table = getCollection();
112         BasicDBObject dbObject = new BasicDBObject();
113         dbObject.put("age", new BasicDBObject("$ne",17));
114         MongoCursor cursor = table.find(dbObject).iterator();
115         while (cursor.hasNext()) {
116             System.out.println(cursor.next());
117         }
118     }
119     /**
120      * 多条件查询
121      */
122     @Test
123     public void findMulti()
124     {
125         MongoCollection table = getCollection();
126         //多条件查询需要先定义一个BasicDBObject数组来存储多个条件
127         List objects = new ArrayList();
128         objects.add(new BasicDBObject("age", new BasicDBObject("$ne", 17)));
129         objects.add(new BasicDBObject("name","zicheng-3"));
130         BasicDBObject query=new BasicDBObject();
131         query.put("$and",objects);
132         MongoCursor cursor = table.find(query).iterator();
133         while (cursor.hasNext()) {
134             System.out.println(cursor.next());
135         }
136     }
137     /**
138      * 通过使用正则表达式模糊查询
139      */
140     @Test
141     public void findRegex()
142     {
143         MongoCollection table = getCollection();
144         BasicDBObject regexQuery = new BasicDBObject();
145         regexQuery.put("name", new BasicDBObject("$regex", "自成.*-[1-8]"));
146         //打印mongodb的查询条件
147        // System.out.println(regexQuery.toString());
148         MongoCursor cursor = table.find(regexQuery).iterator();
149         while (cursor.hasNext()) {
150             System.out.println(cursor.next());
151         }
152     }
153 }