springboot整合mongodb問題1-Decimal128和BigDecimal的轉換之mongodb轉換器使用（轉）

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

1.Decimal128的了解
由於mongodb4.3以上新加了Decimal128類型。Decimal128類型對小數給了最好的支持，而double類型對小數存在精度的問題。個人覺得Decimal128還是不錯的。但是我測試發現spring-data-mongodb 1.*和現在的spring-data-mongodb2.0.5目前不支持Decimal128自動轉換為java的BigDecimal類型。
異常： No converter found capable of converting from type [org.bson.types.Decimal128] to type [java.math.BigDecimal]
大概就是描述：沒有Decimal128轉換成BigDecimal的轉換器。

 

 

 

 

2.訪問mongodb方式：spring-data-mongodb的MongoTemplate。
目前先以spring-data-mongodb的MongoTemplate方式為案例。之后我會增加mongodb原始的dom處理方式，以及spring-boot-starter-data-mongodb下開啟了對Repository的支持方式進行測試一下。（進行了測試）
代碼：https://github.com/topsnowwolf/mongodbit

3.如何解決Decimal128，BigDecimal的類型轉換問題呢？
思路：沒有轉換器我們新加一個轉換。如何新加呢？增加之后如何配置呢？這就是重點了。
首先spring增加類型轉換器有 三種方式。

1.實現GenericConverter接口

2.實現ConverterFactory接口

3.實現Converter接口

這三種方式分別如何實現類型轉換器，我就不多說了。網上很多例子。

下面我就以實現Converter接口方式的來實現。

自定義類型轉換器：

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的源碼。

我們先帶着問題去看。我們增加了轉換器，這個轉換器是給訪問mongodb用的，那肯定是給MongoTemplate設置新的轉換器了。

打開MongoTemplate這個類，果然如此。MongoTemplate的構造方法中就有一個參數是設置類型轉換器的。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);
            }
        }
 
    }

最終發現MongoConverter是一個接口。那一定有實現它的類。查一下api發現，抽象的類AbstractMongoConverter，最后是MappingMongoConverter類。此時就會發現AbstractMongoConverter類中有setCustomConversions設置自定義類型轉換器的set方法。現在興奮了吧！！！

現在大概的思路就是通過創建一個MappingMongoConverter對象，將定義的類型轉換器調用setCustomConversions方法進行注冊。最后調用MongoTemplate的構造方法得到MongoTemplate對象。

廢話不多說上代碼：

自定義一個配置類：

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());//自定義的類型轉換器
        list.add(new Decimal128ToBigDecimalConverter());//自定義的類型轉換器
        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());
    }
}

實體類：

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;
}

測試的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自動生成實體類get/set方法 start-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <!--lombok自動生成實體類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：

#訪問項目的url前綴
server:
  servlet:
    context-path: /mongodb

mongodb的測試數據：

var blacklist1 = {
        "username" : "snowwolf",
        "userid" : "2018001014344",
        "address" : {
                "aCode" : "0020",
                "add" : "廣州"
        },
        "certificate":{
            "certificateid":"20018554111134",
            "certificatetype":"01",
            "desc":"學生證"
        },
       "blacktype" : "01",
       "comments":{
            "cause":"01",
            "desc":"逾期欠費",
            "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":"護照"
        },
       "blacktype" : "01",
       "comments":{
            "cause":"02",
            "desc":"惡意欠費",
            "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" : "廣州"
        },
        "certificate":{
            "certificateid":"20018554111136",
            "certificatetype":"01",
            "desc":"學生證"
        },
       "blacktype":"01",
       "comments":{
            "cause":"03",
            "desc":"公安機關確定的涉嫌短信欺詐、詐騙等犯罪行為的用戶"
       },
       "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中測試：

 

 

結果完美！

 

時間有限，有些地方可能不是很完美！不足之處請大牛指出，謝謝！

有需要代碼的我之后將會發布到git上！

https://github.com/topsnowwolf/mongodbit