建造者模式

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原创最新推荐文章于 2026-04-18 11:47:13 发布 419 阅读 AI 写同款· GEO 优化 ›

CSV文件输入到simulink中将示波器波形和数据CSV文件保存下来进行数据分析。将波形绘制到simulink中阅读详情

建造者模式是将对象的构建封装起来解耦，方便调用者创建复杂的对象，无需知道构建的细节。

常见的使用场景就是一些复杂的连接对象，有非常多的配置，用户不可能清楚每一个属性，所以一般会通过建造者模式来提供属性的默认值，用户只需设置关键的属性，方便调用者使用。

在这里插入图片描述

下面根据nacos源码里的一个例子说明建造者模式

@Data
public class RestResult<T> implements Serializable {

    private static final long serialVersionUID = 6095433538316185017L;

    private int code;

    private String message;

    private T data;

    public RestResult() {
    }

    public RestResult(int code, String message, T data) {
        this.code = code;
        this.setMessage(message);
        this.data = data;
    }

    public RestResult(int code, T data) {
        this.code = code;
        this.data = data;
    }

    public RestResult(int code, String message) {
        this.code = code;
        this.setMessage(message);
    }

    public boolean ok() {
        return this.code == 0 || this.code == 200;
    }

    /**
     * 这里有一些简化，没有继承父类或接口，建造者模式实际可以有不同的实现子类
     */
    public static <T> ResResultBuilder<T> builder() {
        return new ResResultBuilder<T>();
    }

    public static final class ResResultBuilder<T> {

        private int code;

        private String errMsg;

        private T data;

        private ResResultBuilder() {
        }

        public ResResultBuilder<T> withCode(int code) {
            // 当然这里可以再添加一些复杂的逻辑，比如设置了某属性值，其他属性就只能为某些值
            this.code = code;
            return this;
        }

        public ResResultBuilder<T> withMsg(String errMsg) {
            this.errMsg = errMsg;
            return this;
        }

        public ResResultBuilder<T> withData(T data) {
            this.data = data;
            return this;
        }

        /**
         * Build result.
         *
         * @return result
         */
        public RestResult<T> build() {
            RestResult<T> restResult = new RestResult<T>();
            restResult.setCode(code);
            restResult.setMessage(errMsg);
            restResult.setData(data);
            return restResult;
        }
    }
}

下面相当于Director，用于指挥控制对象的创建

public class RestResultUtils {
    
    public static <T> RestResult<T> success() {
        return RestResult.<T>builder().withCode(200).build();
    }
    
    public static <T> RestResult<T> success(T data) {
        return RestResult.<T>builder().withCode(200).withData(data).build();
    }
    
    public static <T> RestResult<T> success(int code, T data) {
        return RestResult.<T>builder().withCode(code).withData(data).build();
    }
    
    public static <T> RestResult<T> failed() {
        return RestResult.<T>builder().withCode(500).build();
    }
    
    public static <T> RestResult<T> failed(int code, T data) {
        return RestResult.<T>builder().withCode(code).withData(data).build();
    }
    
}

应用举例

经常用来提供那些拥有复杂属性的对象，用户可以只设置自己关心的部分属性，如spring框架提供的很多连接对象。

下面拿构建RedisCacheManager的源码举例：

 @Bean
 RedisCacheManager redisCacheManager() {
 	 // 我们使用时只需要设置关键的属性即可
 	 return RedisCacheManager.RedisCacheManagerBuilder
 	 		.fromConnectionFactory(lettuceConnectionFactory)
            .withInitialCacheConfigurations(cacheConfigurationMap)
            .disableCreateOnMissingCache()
            .build();
 }

这里其实也是用到了建造者模式，

public class RedisCacheManager{

    private final RedisCacheWriter cacheWriter;
    private final RedisCacheConfiguration defaultCacheConfig;
    private final Map<String, RedisCacheConfiguration> initialCacheConfiguration;
    private final boolean allowInFlightCacheCreation;

 
    private RedisCacheManager(RedisCacheWriter cacheWriter, RedisCacheConfiguration defaultCacheConfiguration,
                              boolean allowInFlightCacheCreation) {

        Assert.notNull(cacheWriter, "CacheWriter must not be null!");
        Assert.notNull(defaultCacheConfiguration, "DefaultCacheConfiguration must not be null!");

        this.cacheWriter = cacheWriter;
        this.defaultCacheConfig = defaultCacheConfiguration;
        this.initialCacheConfiguration = new LinkedHashMap<>();
        this.allowInFlightCacheCreation = allowInFlightCacheCreation;
    }

    protected RedisCache createRedisCache(String name, @Nullable RedisCacheConfiguration cacheConfig) {
        return new RedisCache(name, cacheWriter, cacheConfig != null ? cacheConfig : defaultCacheConfig);
    }

  	// 通过builder来设置RedisCacheManager属性
    public static class RedisCacheManagerBuilder {

        private RedisCacheWriter cacheWriter;
        private RedisCacheConfiguration defaultCacheConfiguration = RedisCacheConfiguration.defaultCacheConfig();
        private final Map<String, RedisCacheConfiguration> initialCaches = new LinkedHashMap<>();
        private boolean enableTransactions;
        boolean allowInFlightCacheCreation = true;

        private RedisCacheManagerBuilder() {}

        private RedisCacheManagerBuilder(RedisCacheWriter cacheWriter) {
            this.cacheWriter = cacheWriter;
        }

        public static RedisCacheManagerBuilder fromConnectionFactory(RedisConnectionFactory connectionFactory) {
            return new RedisCacheManagerBuilder(new DefaultRedisCacheWriter(connectionFactory));
        }

        public static RedisCacheManagerBuilder fromCacheWriter(RedisCacheWriter cacheWriter) {
            return new RedisCacheManagerBuilder(cacheWriter);
        }

        public RedisCacheManagerBuilder cacheDefaults(RedisCacheConfiguration defaultCacheConfiguration) {
            Assert.notNull(defaultCacheConfiguration, "DefaultCacheConfiguration must not be null!");
            this.defaultCacheConfiguration = defaultCacheConfiguration;
            return this;
        }

        public RedisCacheManagerBuilder transactionAware() {
            this.enableTransactions = true;
            return this;
        }
   
        public RedisCacheManagerBuilder initialCacheNames(Set<String> cacheNames) {
            Assert.notNull(cacheNames, "CacheNames must not be null!");
            cacheNames.forEach(it -> withCacheConfiguration(it, defaultCacheConfiguration));
            return this;
        }

        public RedisCacheManagerBuilder withInitialCacheConfigurations(
            Map<String, RedisCacheConfiguration> cacheConfigurations) {
            Assert.notNull(cacheConfigurations, "CacheConfigurations must not be null!");
            cacheConfigurations.forEach((cacheName, configuration) -> Assert.notNull(configuration,
                String.format("RedisCacheConfiguration for cache %s must not be null!", cacheName)));
            this.initialCaches.putAll(cacheConfigurations);
            return this;
        }

        public RedisCacheManagerBuilder withCacheConfiguration(String cacheName, RedisCacheConfiguration cacheConfiguration) {
            Assert.notNull(cacheName, "CacheName must not be null!");
            Assert.notNull(cacheConfiguration, "CacheConfiguration must not be null!");
            this.initialCaches.put(cacheName, cacheConfiguration);
            return this;
        }
     
        public RedisCacheManagerBuilder disableCreateOnMissingCache() {
            this.allowInFlightCacheCreation = false;
            return this;
        } }

        public RedisCacheManager build() {
            Assert.state(cacheWriter != null, "CacheWriter must not be null! '.");
            RedisCacheManager cm = new RedisCacheManager(cacheWriter, defaultCacheConfiguration, initialCaches, allowInFlightCacheCreation);
            cm.setTransactionAware(enableTransactions);
            return cm;
        }
    }
}