springboot整合mongodb问题1-Decimal128和BigDecimal的转换之mongodb转换器使用（转）

转自：https://blog.csdn.net/weixin_41792559/article/details/79575524

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";
    @Override
    public MongoClient mongoClient() {
        MongoClient mongoClient = new MongoClient();
        return mongoClient;
    }

    @Override
    protected String getDatabaseName() {
        return dbName;
    }
    @Bean
    public 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;
    }
    @Bean
    public MongoDbFactory dbFactory() throws Exception {
        return new SimpleMongoDbFactory(new MongoClientURI("mongodb://localhost:27017/wolf"));
    }
    @Bean
    public MongoMappingContext mongoMappingContext() {
        MongoMappingContext mappingContext = new MongoMappingContext();
        return mappingContext;
    }
    @Bean
    public 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);
    @Autowired
    private 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