1.Decimal128的了解

由于mongodb4.3以上新加了Decimal128类型。Decimal128类型对小数给了最好的支持，而double类型对小数存在精度的问题。个人觉得Decimal128还是不错的。但是我测试发现spring-data-mongodb 1.*和现在的spring-data-mongodb2.0.5目前不支持Decimal128自动转换为java的BigDecimal类型。

异常： No converter found capable of converting from type [org.bson.types.Decimal128] to type [java.math.BigDecimal]

大概就是描述：没有Decimal128转换成BigDecimal的转换器。

2.访问mongodb方式：spring-data-mongodb的MongoTemplate。

目前先以spring-data-mongodb的MongoTemplate方式为案例。之后我会增加mongodb原始的dom处理方式，以及spring-boot-starter-data-mongodb下开启了对Repository的支持方式进行测试一下。（进行了测试）

代码：https://github.com/topsnowwolf/mongodbit

3.如何解决Decimal128，BigDecimal的类型转换问题呢？

思路：没有转换器我们新加一个转换。如何新加呢？增加之后如何配置呢？这就是重点了。

首先spring增加类型转换器有三种方式。

1.实现GenericConverter接口

2.实现ConverterFactory接口

3.实现Converter接口

这三种方式分别如何实现类型转换器，我就不多说了。网上很多例子。

下面我就以实现Converter接口方式的来实现。

自定义类型转换器：

package com.wolf.mongodbit.converter;import org.bson.types.Decimal128;
import org.springframework.core.convert.converter.Converter;
import org.springframework.data.convert.ReadingConverter;
import org.springframework.data.convert.WritingConverter;import java.math.BigDecimal;@ReadingConverter
@WritingConverter
public class BigDecimalToDecimal128Converter implements Converter<BigDecimal, Decimal128> {public Decimal128 convert(BigDecimal bigDecimal) {return new Decimal128(bigDecimal);}}

package com.wolf.mongodbit.converter;import org.bson.types.Decimal128;
import org.springframework.core.convert.converter.Converter;
import org.springframework.data.convert.ReadingConverter;
import org.springframework.data.convert.WritingConverter;import java.math.BigDecimal;@ReadingConverter
@WritingConverter
public class Decimal128ToBigDecimalConverter implements Converter<Decimal128, BigDecimal> {public BigDecimal convert(Decimal128 decimal128) {return decimal128.bigDecimalValue();}}

下面我就分析一下MongoTemplate的源码。

我们先带着问题去看。我们增加了转换器，这个转换器是给访问mongodb用的，那肯定是给MongoTemplate设置新的转换器了。

打开MongoTemplate这个类，果然如此。MongoTemplate的构造方法中就有一个参数是设置类型转换器的。看到希望了。哈哈！

    public MongoTemplate(MongoDbFactory mongoDbFactory, MongoConverter mongoConverter) {this.writeConcernResolver = DefaultWriteConcernResolver.INSTANCE;this.writeResultChecking = WriteResultChecking.NONE;Assert.notNull(mongoDbFactory, "MongoDbFactory must not be null!");this.mongoDbFactory = mongoDbFactory;this.exceptionTranslator = mongoDbFactory.getExceptionTranslator();this.mongoConverter = mongoConverter == null ? getDefaultMongoConverter(mongoDbFactory) : mongoConverter;this.queryMapper = new QueryMapper(this.mongoConverter);this.updateMapper = new UpdateMapper(this.mongoConverter);this.mappingContext = this.mongoConverter.getMappingContext();if (null != this.mappingContext && this.mappingContext instanceof MongoMappingContext) {this.indexCreator = new MongoPersistentEntityIndexCreator((MongoMappingContext)this.mappingContext, mongoDbFactory);this.eventPublisher = new MongoMappingEventPublisher(this.indexCreator);if (this.mappingContext instanceof ApplicationEventPublisherAware) {((ApplicationEventPublisherAware)this.mappingContext).setApplicationEventPublisher(this.eventPublisher);}}}

最终发现MongoConverter是一个接口。那一定有实现它的类。查一下api发现，抽象的类AbstractMongoConverter，最后是MappingMongoConverter类。此时就会发现AbstractMongoConverter类中有setCustomConversions设置自定义类型转换器的set方法。现在兴奋了吧！！！

现在大概的思路就是通过创建一个MappingMongoConverter对象，将定义的类型转换器调用setCustomConversions方法进行注册。最后调用MongoTemplate的构造方法得到MongoTemplate对象。

废话不多说上代码：

自定义一个配置类：

package com.wolf.mongodbit.config;import com.mongodb.MongoClient;
import com.mongodb.MongoClientURI;
import com.wolf.mongodbit.converter.BigDecimalToDecimal128Converter;
import com.wolf.mongodbit.converter.Decimal128ToBigDecimalConverter;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.mongodb.MongoDbFactory;
import org.springframework.data.mongodb.config.AbstractMongoConfiguration;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver;
import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
import org.springframework.data.mongodb.core.convert.MongoCustomConversions;
import org.springframework.data.mongodb.core.mapping.MongoMappingContext;import java.util.ArrayList;
import java.util.List;
@Configuration
public class MongodbConfig extends AbstractMongoConfiguration{private String dbName = "wolf";@Overridepublic MongoClient mongoClient() {MongoClient mongoClient = new MongoClient();return mongoClient;}@Overrideprotected String getDatabaseName() {return dbName;}@Beanpublic MappingMongoConverter mappingMongoConverter() throws Exception {DefaultDbRefResolver dbRefResolver = new DefaultDbRefResolver(this.dbFactory());MappingMongoConverter converter = new MappingMongoConverter(dbRefResolver, this.mongoMappingContext());List<Object> list = new ArrayList<>();list.add(new BigDecimalToDecimal128Converter());//自定义的类型转换器list.add(new Decimal128ToBigDecimalConverter());//自定义的类型转换器converter.setCustomConversions(new MongoCustomConversions(list));return converter;}@Beanpublic MongoDbFactory dbFactory() throws Exception {return new SimpleMongoDbFactory(new MongoClientURI("mongodb://localhost:27017/wolf"));}@Beanpublic MongoMappingContext mongoMappingContext() {MongoMappingContext mappingContext = new MongoMappingContext();return mappingContext;}@Beanpublic MongoTemplate mongoTemplate() throws Exception {return new MongoTemplate(this.dbFactory(), this.mappingMongoConverter());}
}

实体类：

package com.wolf.mongodbit.entity.mongodb;import lombok.Data;@Data
public class Address {private String aCode;private String add;
}

package com.wolf.mongodbit.entity.mongodb;import lombok.Data;
import org.bson.types.ObjectId;
import org.springframework.data.mongodb.core.mapping.Document;import java.util.Date;@Document(collection="blacklist")
@Data
public class Blacklist {private ObjectId objectId;private String username;private String userid;private String blacktype;private String status;private Date update;private Date indate;private Address address;private Comments comments;
}

package com.wolf.mongodbit.entity.mongodb;import lombok.Data;import java.math.BigDecimal;
@Data
public class Comments {private String cause;private String desc;private BigDecimal money;
}

测试的controller：

package com.wolf.mongodbit.controller;import com.wolf.mongodbit.entity.mongodb.Blacklist;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.query.Query;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.List;import static org.springframework.data.mongodb.core.query.Criteria.where;
import static org.springframework.data.mongodb.core.query.Query.query;@RestController
@RequestMapping("/mongodb")
public class BlackListController {private final static Logger logger = LoggerFactory.getLogger(BlackListController.class);@Autowiredprivate MongoTemplate mongoTemplate;@PostMapping("/check")private Blacklist checkBlack(Blacklist blackList){List<Blacklist> list = mongoTemplate.find(query(where("userid").is(blackList.getUserid())), Blacklist.class);logger.info("springboot+mongodb:size={}",list.size());if(list.size()>0)return list.get(0);return null;}
}

pom配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.wolf</groupId><artifactId>mongodbit</artifactId><version>0.0.1-SNAPSHOT</version><packaging>jar</packaging><name>mongodbit</name><description>Demo project for Spring Boot</description><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.0.0.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><!--lombok自动生成实体类get/set方法 start--><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency><!--lombok自动生成实体类get/set方法 end--><!--mongodb引入 start --><dependency><groupId>org.springframework.data</groupId><artifactId>spring-data-mongodb</artifactId></dependency><!--<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-mongodb</artifactId></dependency>--><!--mongodb引入 end --></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

yml配置文件：

#访问项目的url前缀
server:servlet:context-path: /mongodb

mongodb的测试数据：

var blacklist1 = {"username" : "snowwolf","userid" : "2018001014344","address" : {"aCode" : "0020","add" : "广州"},"certificate":{"certificateid":"20018554111134","certificatetype":"01","desc":"学生证"},"blacktype" : "01","comments":{"cause":"01","desc":"逾期欠费","money":NumberDecimal("18889.09")},"status":"01","update" : ISODate("2017-12-06T04:26:18.354Z"),"indate" : ISODate("2017-12-06T04:26:18.354Z")};
var blacklist2 = {"username" : "lison","userid" : "2018001014345","address" : {"aCode" : "0075","add" : "深圳"},"certificate":{"certificateid":"20018554111134","certificatetype":"02","desc":"护照"},"blacktype" : "01","comments":{"cause":"02","desc":"恶意欠费","money":NumberDecimal("188890.00")},"status":"01","update" : ISODate("2016-01-06T04:26:18.354Z"),"indate" : ISODate("2015-12-06T04:26:18.354Z")};
var blacklist3 = {"username":"tom","userid":"2018001014346","address":{"aCode" : "0020","add" : "广州"},"certificate":{"certificateid":"20018554111136","certificatetype":"01","desc":"学生证"},"blacktype":"01","comments":{"cause":"03","desc":"公安机关确定的涉嫌短信欺诈、诈骗等犯罪行为的用户"},"status":"01","update":ISODate("2017-12-06T04:26:18.354Z"),"indate":ISODate("2017-12-06T04:26:18.354Z")};db.blacklist.insert(blacklist1);
db.blacklist.insert(blacklist2);
db.blacklist.insert(blacklist3);

在postman中测试：

结果完美！

时间有限，有些地方可能不是很完美！不足之处请大牛指出，谢谢！

有需要代码的我之后将会发布到git上！

https://github.com/topsnowwolf/mongodbit

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菜鸟入坑》springboot整合mongodb问题1-Decimal128和BigDecimal的转换

1.Decimal128的了解

2.访问mongodb方式：spring-data-mongodb的MongoTemplate。

3.如何解决Decimal128，BigDecimal的类型转换问题呢？

菜鸟入坑》springboot整合mongodb问题1-Decimal128和BigDecimal的转换相关推荐

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