本文实现一个通用泛型封装实现类，需要给定一个集合对象，类似mysql中与java对应的表；思想就是把给定的对象解析出所有非空字段，保存到一个BasicDBObject中，这里一定要保证java对象与mongodb中的文档字段名字一样，因为代码为了实现通用，是默认以java对象的字段为BasicDBObject的查询字段。

核心代码1：这是将java对象转换为查询条件。/**

* 通过反射获取非空字段信息

* @param record

* @param

* @return

*/

private BasicDBObject getCondition(Q record) {

BasicDBObject cond = new BasicDBObject();

Class clazz = record.getClass();

Field[] fields = clazz.getDeclaredFields();

for (Field field : fields) {

try {

field.setAccessible(true);

Object value = field.get(record);

if (value != null)

cond.put(field.getName(), value);

} catch (IllegalAccessException e) {

e.printStackTrace();

}

}

return cond;

}

核心代码2：这是将查询到的文档转换为java对象，这里也是默认java对象的字段和数据库文档字段一样，也是利用java的反射动态获取用户自定义对象的所有字段，然后进行赋值，我在赋值过程中单独判断了int和long型，因为插入mongodb的时候一般是以double存的，这样就会造成转型错误。/**

* 将结果转化为自定义对象

* @param document

* @param target

* @param

* @return

*/

private Q parseToObject(Document document, Class target) {

try {

Q result = target.newInstance();

Field[] fields = target.getDeclaredFields();

for (Field f : fields) {

f.setAccessible(true);

Object value = document.get(f.getName());

if (value == null)

continue;

else if (f.getType() == Integer.class)

f.set(result, ((Number) value).intValue());

else if (f.getType() == Long.class)

f.set(result, ((Number) value).longValue());

else

f.set(result, document.get(f.getName(), f.getType()));

}

return result;

} catch (IllegalAccessException e) {

e.printStackTrace();

return null;

} catch (InstantiationException e) {

e.printStackTrace();

return null;

}

}

调用方法：先转换查询参数，查询的时候是以id来判断正序倒序，所以默认数据库中一定要有id的标识字段。public List queryByCondition(BaseQuery query,boolean up) {

Q record = query.getQuery();

BasicDBObject cond = getCondition(record);

FindIterable findIterable;

if (query.getStart() != null && query.getRows() != null)

findIterable = thisCollection().find(cond)

.sort(new BasicDBObject("id", up ? 1 : -1))

.skip((query.getStart() - 1) * query.getRows())

.limit(query.getRows());

else

findIterable = thisCollection().find(cond)

.sort(new BasicDBObject("id", up ? 1 : -1));

MongoCursor iterator = findIterable.iterator();

List result = new ArrayList<>();

while (iterator.hasNext()) {

Document document = iterator.next();

result.add((Q) parseToObject(document, record.getClass()));

}

iterator.close();

return result;

}

这里传入的BaseQuery如下：里面的query就是个需要查询的java对象，start&rows是为了用来分页的。这里是用到了lombok的插件，这样简化很多的gettter&setter等代码。@Setter

@Getter

@NoArgsConstructor

@AllArgsConstructor

@Data

@Accessors(chain = true)

public class BaseQuery {

private Integer start;

private Integer rows;

private Q query;

public BaseQuery(Class clazz) {

try {

this.query = (Q) clazz.newInstance();

} catch (InstantiationException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

e.printStackTrace();

}

}

}

测试条件查询方法：这里用到的实体如下：@Data

@AllArgsConstructor

@NoArgsConstructor

@Accessors(chain = true)

public class User_info {

private Integer id;

private String name;

private Integer age;

private Integer role;

}public static void main(String[] args) {

User_info record = new User_info();

BaseQuery query = new BaseQuery<>();

query.setQuery(record);

BaseMongoDao dao = new BaseMongoDao("test");

List result = dao.queryByCondition(query, true);

for (User_info user : result) {

System.out.println(user);

}

}

因为这里用到的查询条件为空，所有会匹配数据库的所有项：

现在测试一下设置权限为1的数据：public static void main(String[] args) {

User_info record = new User_info();

record.setRole(1);

BaseQuery query = new BaseQuery<>();

query.setQuery(record);

BaseMongoDao dao = new BaseMongoDao("test");

List result = dao.queryByCondition(query, true);

for (User_info user : result) {

System.out.println(user);

}

}

输出：

这个条件查询方法是一个例子，其他的删除，增加，修改都是这个原理，下面带有：

1.public List queryByCondition(BaseQuery query,boolean up)

2.public Integer queryCoditionCount(BaseQuery query)

3.public boolean insertOne(Q record)

4.public boolean insertList(List records)

5.public boolean deleteById(Integer id)

6.public boolean deleteByIds(List ids)

7.public void updateById(Q record)

放上所有代码：package cn.wzy.dao;

import com.mongodb.*;

import com.mongodb.client.FindIterable;

import com.mongodb.client.MongoCollection;

import com.mongodb.client.MongoCursor;

import com.mongodb.client.MongoDatabase;

import org.bson.Document;

import org.cn.wzy.query.BaseQuery;

import org.cn.wzy.util.PropertiesUtil;

import java.lang.reflect.Field;

import java.util.ArrayList;

import java.util.List;

/**

* Create by Wzy

* on 2018/7/28 18:15

* 不短不长八字刚好

*/

public class BaseMongoDao {

private static final MongoClient mongoClient;

private static final MongoDatabase mongo;

static {

MongoClientOptions options = MongoClientOptions.builder()

.connectionsPerHost(150)

.maxWaitTime(2000)

.socketTimeout(2000)

.maxConnectionLifeTime(5000)

.connectTimeout(5000).build();

ServerAddress serverAddress = new ServerAddress(PropertiesUtil.StringValue("mongo.host"),

PropertiesUtil.IntegerValue("mongo.port"));

List addrs = new ArrayList<>();

addrs.add(serverAddress);

MongoCredential credential = MongoCredential.createScramSha1Credential(

PropertiesUtil.StringValue("mongo.user")

, PropertiesUtil.StringValue("mongo.db")

, PropertiesUtil.StringValue("mongo.pwd").toCharArray());

mongoClient = new MongoClient(addrs, credential, options);

mongo = mongoClient.getDatabase(PropertiesUtil.StringValue("mongo.db"));

}

public BaseMongoDao(String colName) {

this.colName = colName;

}

private String colName;

private MongoCollection thisCollection() {

return mongo.getCollection(colName);

}

public List queryByCondition(BaseQuery query,boolean up) {

Q record = query.getQuery();

BasicDBObject cond = getCondition(record);

FindIterable findIterable;

if (query.getStart() != null && query.getRows() != null)

findIterable = thisCollection().find(cond)

.sort(new BasicDBObject("id", up ? 1 : -1))

.skip((query.getStart() - 1) * query.getRows())

.limit(query.getRows());

else

findIterable = thisCollection().find(cond)

.sort(new BasicDBObject("id", up ? 1 : -1));

MongoCursor iterator = findIterable.iterator();

List result = new ArrayList<>();

while (iterator.hasNext()) {

Document document = iterator.next();

result.add((Q) parseToObject(document, record.getClass()));

}

iterator.close();

return result;

}

public Integer queryCoditionCount(BaseQuery query) {

Q record = query.getQuery();

BasicDBObject cond = getCondition(record);

return (int) thisCollection().countDocuments(cond);

}

public boolean insertOne(Q record) {

BasicDBObject cond = getCondition(record);

try {

int top = getTop();

cond.put("id",++top);

thisCollection().insertOne(new Document(cond));

return true;

} catch (Exception e) {

e.printStackTrace();

return false;

}

}

public boolean insertList(List records) {

try {

List list = new ArrayList<>(records.size());

if (!changeIds(records))

return false;

for (Q record : records) {

list.add(new Document(getCondition(record)));

}

thisCollection().insertMany(list);

return true;

}catch (Exception e) {

e.printStackTrace();

return false;

}

}

public boolean deleteById(Integer id) {

try {

if (id == null)

return false;

thisCollection().deleteOne(new BasicDBObject("id",id));

return true;

} catch (Exception e) {

e.printStackTrace();

return false;

}

}

public boolean deleteByIds(List ids) {

BasicDBObject cond = new BasicDBObject("id",new BasicDBObject("$in",ids.toArray()));

try {

thisCollection().deleteMany(cond);

return true;

} catch (Exception e) {

e.printStackTrace();

return false;

}

}

/**

* 只通过id更改，查询就只是搜索id

* @param record

* @param

*/

public void updateById(Q record) {

BasicDBObject cond = getCondition(record);

BasicDBObject update = new BasicDBObject("$set",cond);

BasicDBObject query = new BasicDBObject("id",cond.get("id"));

thisCollection().updateOne(query,update);

}

/**

* 通过反射获取非空字段信息

* @param record

* @param

* @return

*/

private BasicDBObject getCondition(Q record) {

BasicDBObject cond = new BasicDBObject();

Class clazz = record.getClass();

Field[] fields = clazz.getDeclaredFields();

for (Field field : fields) {

try {

field.setAccessible(true);

Object value = field.get(record);

if (value != null)

cond.put(field.getName(), value);

} catch (IllegalAccessException e) {

e.printStackTrace();

}

}

return cond;

}

/**

* 将结果转化为自定义对象

* @param document

* @param target

* @param

* @return

*/

private Q parseToObject(Document document, Class target) {

try {

Q result = target.newInstance();

Field[] fields = target.getDeclaredFields();

for (Field f : fields) {

f.setAccessible(true);

Object value = document.get(f.getName());

if (value == null)

continue;

else if (f.getType() == Integer.class)

f.set(result, ((Number) value).intValue());

else if (f.getType() == Long.class)

f.set(result, ((Number) value).longValue());

else

f.set(result, document.get(f.getName(), f.getType()));

}

return result;

} catch (IllegalAccessException e) {

e.printStackTrace();

return null;

} catch (InstantiationException e) {

e.printStackTrace();

return null;

}

}

/**

* 使id自增

* @param records

* @param

* @return

*/

private boolean changeIds(List records) {

if (records == null || records.size() == 0)

return false;

Class clazz = records.get(0).getClass();

try {

Field id = clazz.getDeclaredField("id");

id.setAccessible(true);

int top = getTop();

for (Q record: records) {

id.set(record,++top);

}

} catch (NoSuchFieldException e) {

e.printStackTrace();

return false;

} catch (IllegalAccessException e) {

e.printStackTrace();

return false;

}

return true;

}

/**

* 查找顶针

* @return

*/

private int getTop() {

return ((Number) thisCollection().find().sort(new BasicDBObject("id",-1)).first().get("id")).intValue();

}

}

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