springboot集成redisson(starter)单机模式启动报错(password)

问题点：
springboot集成Redisson单机版时配置如下：
spring boot版本：
2.3.1.RELEASE

Redisson依赖：

<dependency>
    <groupId>org.redisson</groupId>
    <artifactId>redisson-spring-boot-starter</artifactId>
    <version>3.13.3</version>
</dependency>

application.yml配置：

spring:
  redis:
    host: 127.0.0.1
    port: 6379
    password:

启动项目发现异常：（精简）

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'redisson' defined in class path resource [org/redisson/spring/starter/RedissonAutoConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.redisson.api.RedissonClient]: Factory method 'redisson' threw exception; nested exception is org.redisson.client.RedisConnectionException: Unable to connect to Redis server: /127.0.0.1:6379

Caused by: org.redisson.client.RedisException: ERR Client sent AUTH, but no password is set. channel: [id: 0xd70ac938, L:/127.0.0.1:11349 - R:/127.0.0.1:6379] command: (AUTH), params: (password masked)

在异常上可以看出
第一个异常：创建RedissonClient客户端的时候出现了异常
第二个异常：没有设置密码（本地Redis没有设置密码）

查看RedissonClient客户端创建的源代码：

/**
 * Copyright (c) 2013-2020 Nikita Koksharov
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.redisson.spring.starter;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.redisson.Redisson;
import org.redisson.api.RedissonClient;
import org.redisson.config.Config;
import org.redisson.spring.data.connection.RedissonConnectionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.AutoConfigureBefore;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration;
import org.springframework.boot.autoconfigure.data.redis.RedisProperties;
import org.springframework.boot.autoconfigure.data.redis.RedisProperties.Sentinel;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.Resource;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisOperations;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.util.ReflectionUtils;

/**
 * 
 * @author Nikita Koksharov
 * @author Nikos Kakavas (https://github.com/nikakis)
 *
 */
@Configuration
@ConditionalOnClass({Redisson.class, RedisOperations.class})
@AutoConfigureBefore(RedisAutoConfiguration.class)
@EnableConfigurationProperties({RedissonProperties.class, RedisProperties.class})
public class RedissonAutoConfiguration {

    @Autowired(required = false)
    private List<RedissonAutoConfigurationCustomizer> redissonAutoConfigurationCustomizers;

    @Autowired
    private RedissonProperties redissonProperties;
    
    @Autowired
    private RedisProperties redisProperties;
    
    @Autowired
    private ApplicationContext ctx;
    
    @Bean
    @ConditionalOnMissingBean(name = "redisTemplate")
    public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory) {
        RedisTemplate<Object, Object> template = new RedisTemplate<Object, Object>();
        template.setConnectionFactory(redisConnectionFactory);
        return template;
    }

    @Bean
    @ConditionalOnMissingBean(StringRedisTemplate.class)
    public StringRedisTemplate stringRedisTemplate(RedisConnectionFactory redisConnectionFactory) {
        StringRedisTemplate template = new StringRedisTemplate();
        template.setConnectionFactory(redisConnectionFactory);
        return template;
    }

    @Bean
    @ConditionalOnMissingBean(RedisConnectionFactory.class)
    public RedissonConnectionFactory redissonConnectionFactory(RedissonClient redisson) {
        return new RedissonConnectionFactory(redisson);
    }
    
    @Bean(destroyMethod = "shutdown")
    @ConditionalOnMissingBean(RedissonClient.class)
    public RedissonClient redisson() throws IOException {
        Config config = null;
        Method clusterMethod = ReflectionUtils.findMethod(RedisProperties.class, "getCluster");
        Method timeoutMethod = ReflectionUtils.findMethod(RedisProperties.class, "getTimeout");
        Object timeoutValue = ReflectionUtils.invokeMethod(timeoutMethod, redisProperties);
        int timeout;
        if(null == timeoutValue){
            timeout = 10000;
        }else if (!(timeoutValue instanceof Integer)) {
            Method millisMethod = ReflectionUtils.findMethod(timeoutValue.getClass(), "toMillis");
            timeout = ((Long) ReflectionUtils.invokeMethod(millisMethod, timeoutValue)).intValue();
        } else {
            timeout = (Integer)timeoutValue;
        }
        
        if (redissonProperties.getConfig() != null) {
            try {
                InputStream is = getConfigStream();
                config = Config.fromJSON(is);
            } catch (IOException e) {
                // trying next format
                try {
                    InputStream is = getConfigStream();
                    config = Config.fromYAML(is);
                } catch (IOException e1) {
                    throw new IllegalArgumentException("Can't parse config", e1);
                }
            }
        } else if (redisProperties.getSentinel() != null) {
            Method nodesMethod = ReflectionUtils.findMethod(Sentinel.class, "getNodes");
            Object nodesValue = ReflectionUtils.invokeMethod(nodesMethod, redisProperties.getSentinel());
            
            String[] nodes;
            if (nodesValue instanceof String) {
                nodes = convert(Arrays.asList(((String)nodesValue).split(",")));
            } else {
                nodes = convert((List<String>)nodesValue);
            }
            
            config = new Config();
            config.useSentinelServers()
                .setMasterName(redisProperties.getSentinel().getMaster())
                .addSentinelAddress(nodes)
                .setDatabase(redisProperties.getDatabase())
                .setConnectTimeout(timeout)
                .setPassword(redisProperties.getPassword());
        } else if (clusterMethod != null && ReflectionUtils.invokeMethod(clusterMethod, redisProperties) != null) {
            Object clusterObject = ReflectionUtils.invokeMethod(clusterMethod, redisProperties);
            Method nodesMethod = ReflectionUtils.findMethod(clusterObject.getClass(), "getNodes");
            List<String> nodesObject = (List) ReflectionUtils.invokeMethod(nodesMethod, clusterObject);
            
            String[] nodes = convert(nodesObject);
            
            config = new Config();
            config.useClusterServers()
                .addNodeAddress(nodes)
                .setConnectTimeout(timeout)
                .setPassword(redisProperties.getPassword());
        } else {
            config = new Config();
            String prefix = "redis://";
            Method method = ReflectionUtils.findMethod(RedisProperties.class, "isSsl");
            if (method != null && (Boolean)ReflectionUtils.invokeMethod(method, redisProperties)) {
                prefix = "rediss://";
            }
            
            config.useSingleServer()
                .setAddress(prefix + redisProperties.getHost() + ":" + redisProperties.getPort())
                .setConnectTimeout(timeout)
                .setDatabase(redisProperties.getDatabase())
                .setPassword(redisProperties.getPassword());
        }
        if (redissonAutoConfigurationCustomizers != null) {
            for (RedissonAutoConfigurationCustomizer customizer : redissonAutoConfigurationCustomizers) {
                customizer.customize(config);
            }
        }
        return Redisson.create(config);
    }

    private String[] convert(List<String> nodesObject) {
        List<String> nodes = new ArrayList<String>(nodesObject.size());
        for (String node : nodesObject) {
            if (!node.startsWith("redis://") && !node.startsWith("rediss://")) {
                nodes.add("redis://" + node);
            } else {
                nodes.add(node);
            }
        }
        return nodes.toArray(new String[nodes.size()]);
    }

    private InputStream getConfigStream() throws IOException {
        Resource resource = ctx.getResource(redissonProperties.getConfig());
        InputStream is = resource.getInputStream();
        return is;
    }

    
}

在以上源代码中，redisson()方法是创建RedissonClient客户端的，通过断点调试发现，实际有效代码如下：

将这段代码copy出来自己实现RedissonClient

@Bean
public RedissonClient redissonClient() {
    Config config = new Config();
    config.useSingleServer()
            .setAddress("redis://127.0.0.1:6379");
//                .setConnectTimeout(timeout) // 未设置使用默认
//                .setDatabase(redisProperties.getDatabase()) // 未设置使用默认
//                .setPassword(redisProperties.getPassword()); // 未设置使用默认
    return Redisson.create(config);
}

结果成功启动。

那么问题差异在哪呢？
两个创建RedissonClient的差异点关键在于Config()方法中的useSingleServer()

public SingleServerConfig useSingleServer() {
    return useSingleServer(new SingleServerConfig());
}

我这里通过对比两种创建RedissonClient方式进行对比：
1、通过自定义Bean创建
2、通过框架自动创建

问题点就在于这个password的问题，在配置文件配置了空的password，Redisson解析RedisProperties会将空的password解析成空字符串导致异常。

解决方案：
在yml配置中把空password注释掉

spring:
  redis:
    host: 127.0.0.1
    port: 6379
#    以下password没有值的话，注释掉，不然创建RedissonClient客户端的时候会解析RedisProperties配置成""空字符串导致启动报错，正常是需要解析成null
#    password: