因为今天开发遇到了性能问题，可能与MongoDB的连接有关，所以稍稍深入看了一下，正好搜到原来有人写过这篇相关的内容，所以转载过来。回头有时间可以写个扩展到SpringForAll里，主体思路还是一样的。感谢这位美女程序媛的文章！
说明
Spring Boot中通过依赖 spring-boot-starter-data-mongodb ，来实现 spring-data-mongodb 的自动配置。
但是默认情况下，Spring Boot 中，并没有像使用MySQL或者Redis一样，提供了连接池配置的功能。因此，我们需要自行重写 MongoDbFactory ，实现MongoDB客户端连接的参数配置扩展。
需要说明的是，MongoDB的客户端本身就是一个连接池，因此，我们只需要配置客户端即可。
配置文件
为了统一Spring Boot的配置，我们要将重写的配置也配置到 application.yml 中，前缀为 spring.data.mongodb.custom 下（前缀可自己随意配置）：
spring: data: mongodb: custom: hosts: - 10.0.5.1 - 10.0.5.1 ports: - 27017 - 27018 replica-set: mgset-3590061 username: jancee password: abc123 database: jancee authentication-database: admin connections-per-host: 20 min-connections-per-host: 20该配置例子中，配置了副本集，其中包含了主机 10.0.5.1:27017 和 10.0.5.1:27018 ，其它配置与Spring Boot的标准配置类似，另外， connections-per-host 为客户端的连接数， in-connections-per-host 为客户端最小连接数。
将配置包装成类
为方便调用和可读性，将上述配置包装成一个配置实体类， MongoConfig.java 代码如下:
package com.feidiao.jancee.fdiot.api.config.mongo;import org.hibernate.validator.constraints.NotBlank;import org.hibernate.validator.constraints.NotEmpty;import org.springframework.stereotype.Component;import org.springframework.validation.annotation.Validated;import java.util.List;@Component@Validatedpublic class MongoSettingsProperties { @NotBlank private String database; @NotEmpty private List hosts; @NotEmpty private List ports; private String replicaSet; private String username; private String password; private String authenticationDatabase; private Integer minConnectionsPerHost = 10; private Integer connectionsPerHost = 2; public MongoSettingsProperties() { } public String getDatabase() { return database; } public void setDatabase(String database) { this.database = database; } public List getHosts() { return hosts; } public void setHosts(List hosts) { this.hosts = hosts; } public List getPorts() { return ports; } public void setPorts(List ports) { this.ports = ports; } public String getReplicaSet() { return replicaSet; } public void setReplicaSet(String replicaSet) { this.replicaSet = replicaSet; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getAuthenticationDatabase() { return authenticationDatabase; } public void setAuthenticationDatabase(String authenticationDatabase) { this.authenticationDatabase = authenticationDatabase; } public Integer getMinConnectionsPerHost() { return minConnectionsPerHost; } public void setMinConnectionsPerHost(Integer minConnectionsPerHost) { this.minConnectionsPerHost = minConnectionsPerHost; } public Integer getConnectionsPerHost() { return connectionsPerHost; } public void setConnectionsPerHost(Integer connectionsPerHost) { this.connectionsPerHost = connectionsPerHost; }}覆盖MongoDbFactory
接下来，就是覆盖Spring Boot原有的 MongoDbFactory Bean，新建文件 MongoConfig.java ，代码如下：
import com.mongodb.MongoClient;import com.mongodb.MongoClientOptions;import com.mongodb.MongoCredential;import com.mongodb.ServerAddress;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.context.properties.ConfigurationProperties;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.data.mongodb.MongoDbFactory;import org.springframework.data.mongodb.core.SimpleMongoDbFactory;import java.util.ArrayList;import java.util.List;@Configurationpublic class MongoConfig { // 注入配置实体 @Autowired private MongoSettingsProperties mongoSettingsProperties; @Bean @ConfigurationProperties( prefix = "spring.data.mongodb.custom") MongoSettingsProperties mongoSettingsProperties() { return new MongoSettingsProperties(); } // 覆盖默认的MongoDbFactory @Bean MongoDbFactory mongoDbFactory() { //客户端配置（连接数、副本集群验证） MongoClientOptions.Builder builder = new MongoClientOptions.Builder(); builder.connectionsPerHost(mongoSettingsProperties.getConnectionsPerHost()); builder.minConnectionsPerHost(mongoSettingsProperties.getMinConnectionsPerHost()); if (mongoSettingsProperties.getReplicaSet() != null) { builder.requiredReplicaSetName(mongoSettingsProperties.getReplicaSet()); } MongoClientOptions mongoClientOptions = builder.build(); // MongoDB地址列表 List serverAddresses = new ArrayList(); for (String host : mongoSettingsProperties.getHosts()) { Integer index = mongoSettingsProperties.getHosts().indexOf(host); Integer port = mongoSettingsProperties.getPorts().get(index); ServerAddress serverAddress = new ServerAddress(host, port); serverAddresses.add(serverAddress); } System.out.println("serverAddresses:" + serverAddresses.toString()); // 连接认证 List mongoCredentialList = new ArrayList(); if (mongoSettingsProperties.getUsername() != null) { mongoCredentialList.add(MongoCredential.createScramSha1Credential( mongoSettingsProperties.getUsername(), mongoSettingsProperties.getAuthenticationDatabase() != null ? mongoSettingsProperties.getAuthenticationDatabase() : mongoSettingsProperties.getDatabase(), mongoSettingsProperties.getPassword().toCharArray())); } System.out.println("mongoCredentialList:" + mongoCredentialList.toString()); //创建客户端和Factory MongoClient mongoClient = new MongoClient(serverAddresses, mongoCredentialList, mongoClientOptions); MongoDbFactory mongoDbFactory = new SimpleMongoDbFactory(mongoClient, mongoSettingsProperties.getDatabase()); return mongoDbFactory; }}在这里，实现了MongoDB连接时，前面配置的参数的设置，按照自己的实际情况，可以在 new SimpleMongoDbFactory 时，增加修改自己需要的配置参数。
至此，就完成了全部配置，运行测试即可。
以上就是