开源框架编码技巧一(设计模式篇)

一、建造者模式.  

 1、MyBatis框架的环境类创建，通过静态内部类实现.

public final class Environment {
  // 环境ID
  private final String id;
  // 事务工厂 
  private final TransactionFactory transactionFactory;
  // 数据源
  private final DataSource dataSource;

  public Environment(String id, TransactionFactory transactionFactory, DataSource dataSource) {
    // 1、构造方法中做一些必要的参数校验
    if (id == null) {
      throw new IllegalArgumentException("Parameter 'id' must not be null");
    }
    if (transactionFactory == null) {
      throw new IllegalArgumentException("Parameter 'transactionFactory' must not be null");
    }
    this.id = id;
    if (dataSource == null) {
      throw new IllegalArgumentException("Parameter 'dataSource' must not be null");
    }
    this.transactionFactory = transactionFactory;
    this.dataSource = dataSource;
  }
  // 2、静态内部类实现Builder
  public static class Builder {
    private String id;
    private TransactionFactory transactionFactory;
    private DataSource dataSource;

    public Builder(String id) {
      this.id = id;
    }

    public Builder transactionFactory(TransactionFactory transactionFactory) {
      this.transactionFactory = transactionFactory;
      return this;
    }

    public Builder dataSource(DataSource dataSource) {
      this.dataSource = dataSource;
      return this;
    }

    public String id() {
      return this.id;
    }
    // 3、建造者
    public Environment build() {
      return new Environment(this.id, this.transactionFactory, this.dataSource);
    }

  }

  public String getId() {
    return this.id;
  }

  public TransactionFactory getTransactionFactory() {
    return this.transactionFactory;
  }

  public DataSource getDataSource() {
    return this.dataSource;
  }

}

 使用方式：

new Environment.Builder(id).transactionFactory(xx).dataSource(xx).build();

2、Swagger的接口管理的建造者模式,通过外部类来实现.

// 定义接口管理基本信息
public ApiInfo(
      String title,
      String description,
      String version,
      String termsOfServiceUrl,
      Contact contact,
      String license,
      String licenseUrl,
      Collection<VendorExtension> vendorExtensions) {
    this.title = title;
    this.description = description;
    this.version = version;
    this.termsOfServiceUrl = termsOfServiceUrl;
    this.contact = contact;
    this.license = license;
    this.licenseUrl = licenseUrl;
    this.vendorExtensions = new ArrayList<>(vendorExtensions);
  }

  public String getTitle() {
    return title;
  }

  public String getDescription() {
    return description;
  }

  public String getTermsOfServiceUrl() {
    return termsOfServiceUrl;
  }

  public Contact getContact() {
    return contact;
  }

  public String getLicense() {
    return license;
  }

  public String getLicenseUrl() {
    return licenseUrl;
  }

  public String getVersion() {
    return version;
  }

  public List<VendorExtension> getVendorExtensions() {
    return vendorExtensions;
  }
}

// 定义建造者类
public class ApiInfoBuilder {
  private String title;
  private String description;
  private String termsOfServiceUrl;
  private Contact contact;
  private String license;
  private String licenseUrl;
  private String version;
  private final List<VendorExtension> vendorExtensions = new ArrayList<>();

  /**
   * Updates the api title
   *
   * @param title - title for the API
   * @return this
   */
  public ApiInfoBuilder title(String title) {
    this.title = title;
    return this;
  }

  /**
   * Updates the api description
   *
   * @param description - api description
   * @return this
   */
  public ApiInfoBuilder description(String description) {
    this.description = description;
    return this;
  }

  /**
   * Updates the terms of service url
   *
   * @param termsOfServiceUrl - url to the terms of service
   * @return this
   */
  public ApiInfoBuilder termsOfServiceUrl(String termsOfServiceUrl) {
    this.termsOfServiceUrl = termsOfServiceUrl;
    return this;
  }

  /**
   * Updates the api version
   *
   * @param version - of the API
   * @return this
   */
  public ApiInfoBuilder version(String version) {
    this.version = version;
    return this;
  }

  /**
   * Updates contact information for the person responsible for this API
   *
   * @param contact - contact information
   * @return this
   */
  public ApiInfoBuilder contact(Contact contact) {
    this.contact = contact;
    return this;
  }

  /**
   * Updates license information for this API
   *
   * @param license licence string
   * @return this
   */
  public ApiInfoBuilder license(String license) {
    this.license = license;
    return this;
  }

  /**
   * Updates the license Url for this API
   *
   * @param licenseUrl - license Url
   * @return this
   */
  public ApiInfoBuilder licenseUrl(String licenseUrl) {
    this.licenseUrl = licenseUrl;
    return this;
  }

  /**
   * Adds extensions for this API
   *
   * @param extensions -  extensions
   * @return this
   */
  public ApiInfoBuilder extensions(List<VendorExtension> extensions) {
    this.vendorExtensions.addAll(nullToEmptyList(extensions));
    return this;
  }

  public ApiInfo build() {
    return new ApiInfo(title, description, version, termsOfServiceUrl, contact, license, licenseUrl, vendorExtensions);
  }
}

使用方式：

private ApiInfo apiInfo() {
    return new ApiInfoBuilder().title("Swagger3.x接口文档").description("项目前后端接口文档").contact(new Contact("Jack", "https://XXX", "xxx@qq.com"))
            .version("1.0.0").build();
}

3、Nacos的实例构造器建造者模式.

package com.alibaba.nacos.api.naming.pojo;

import com.alibaba.nacos.api.common.Constants;
import com.alibaba.nacos.api.naming.PreservedMetadataKeys;
import com.alibaba.nacos.api.utils.StringUtils;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonInclude.Include;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

import static com.alibaba.nacos.api.common.Constants.NUMBER_PATTERN;

/**
 * Instance.
 *
 * @author nkorange
 */
@JsonInclude(Include.NON_NULL)
public class Instance implements Serializable {
    
    private static final long serialVersionUID = -742906310567291979L;
    
    /**
     * unique id of this instance.
     */
    private String instanceId;
    
    /**
     * instance ip.
     */
    private String ip;
    
    /**
     * instance port.
     */
    private int port;
    
    /**
     * instance weight.
     */
    private double weight = 1.0D;
    
    /**
     * instance health status.
     */
    private boolean healthy = true;
    
    /**
     * If instance is enabled to accept request.
     */
    private boolean enabled = true;
    
    /**
     * If instance is ephemeral.
     *
     * @since 1.0.0
     */
    private boolean ephemeral = true;
    
    /**
     * cluster information of instance.
     */
    private String clusterName;
    
    /**
     * Service information of instance.
     */
    private String serviceName;
    
    /**
     * user extended attributes.
     */
    private Map<String, String> metadata = new HashMap<String, String>();
    
    public String getInstanceId() {
        return this.instanceId;
    }
    
    public void setInstanceId(final String instanceId) {
        this.instanceId = instanceId;
    }
    
    public String getIp() {
        return this.ip;
    }
    
    public void setIp(final String ip) {
        this.ip = ip;
    }
    
    public int getPort() {
        return this.port;
    }
    
    public void setPort(final int port) {
        this.port = port;
    }
    
    public double getWeight() {
        return this.weight;
    }
    
    public void setWeight(final double weight) {
        this.weight = weight;
    }
    
    public boolean isHealthy() {
        return this.healthy;
    }
    
    public void setHealthy(final boolean healthy) {
        this.healthy = healthy;
    }
    
    public String getClusterName() {
        return this.clusterName;
    }
    
    public void setClusterName(final String clusterName) {
        this.clusterName = clusterName;
    }
    
    public String getServiceName() {
        return this.serviceName;
    }
    
    public void setServiceName(final String serviceName) {
        this.serviceName = serviceName;
    }
    
    public Map<String, String> getMetadata() {
        return this.metadata;
    }
    
    public void setMetadata(final Map<String, String> metadata) {
        this.metadata = metadata;
    }
    
    /**
     * add meta data.
     *
     * @param key   meta data key
     * @param value meta data value
     */
    public void addMetadata(final String key, final String value) {
        if (metadata == null) {
            metadata = new HashMap<String, String>(4);
        }
        metadata.put(key, value);
    }
    
    public boolean isEnabled() {
        return this.enabled;
    }
    
    public void setEnabled(final boolean enabled) {
        this.enabled = enabled;
    }
    
    public boolean isEphemeral() {
        return this.ephemeral;
    }
    
    public void setEphemeral(final boolean ephemeral) {
        this.ephemeral = ephemeral;
    }
    
    @Override
    public String toString() {
        return "Instance{" + "instanceId='" + instanceId + '\'' + ", ip='" + ip + '\'' + ", port=" + port + ", weight="
                + weight + ", healthy=" + healthy + ", enabled=" + enabled + ", ephemeral=" + ephemeral
                + ", clusterName='" + clusterName + '\'' + ", serviceName='" + serviceName + '\'' + ", metadata="
                + metadata + '}';
    }
    
    public String toInetAddr() {
        return ip + ":" + port;
    }
    
    @Override
    public boolean equals(final Object obj) {
        if (!(obj instanceof Instance)) {
            return false;
        }
        
        final Instance host = (Instance) obj;
        return Instance.strEquals(host.toString(), toString());
    }
    
    @Override
    public int hashCode() {
        return toString().hashCode();
    }
    
    private static boolean strEquals(final String str1, final String str2) {
        return str1 == null ? str2 == null : str1.equals(str2);
    }
    
    public long getInstanceHeartBeatInterval() {
        return getMetaDataByKeyWithDefault(PreservedMetadataKeys.HEART_BEAT_INTERVAL,
                Constants.DEFAULT_HEART_BEAT_INTERVAL);
    }
    
    public long getInstanceHeartBeatTimeOut() {
        return getMetaDataByKeyWithDefault(PreservedMetadataKeys.HEART_BEAT_TIMEOUT,
                Constants.DEFAULT_HEART_BEAT_TIMEOUT);
    }
    
    public long getIpDeleteTimeout() {
        return getMetaDataByKeyWithDefault(PreservedMetadataKeys.IP_DELETE_TIMEOUT,
                Constants.DEFAULT_IP_DELETE_TIMEOUT);
    }
    
    public String getInstanceIdGenerator() {
        return getMetaDataByKeyWithDefault(PreservedMetadataKeys.INSTANCE_ID_GENERATOR,
                Constants.DEFAULT_INSTANCE_ID_GENERATOR);
    }
    
    /**
     * Returns {@code true} if this metadata contains the specified key.
     *
     * @param key metadata key
     * @return {@code true} if this metadata contains the specified key
     */
    public boolean containsMetadata(final String key) {
        if (getMetadata() == null || getMetadata().isEmpty()) {
            return false;
        }
        return getMetadata().containsKey(key);
    }
    
    private long getMetaDataByKeyWithDefault(final String key, final long defaultValue) {
        if (getMetadata() == null || getMetadata().isEmpty()) {
            return defaultValue;
        }
        final String value = getMetadata().get(key);
        if (!StringUtils.isEmpty(value) && value.matches(NUMBER_PATTERN)) {
            return Long.parseLong(value);
        }
        return defaultValue;
    }
    
    private String getMetaDataByKeyWithDefault(final String key, final String defaultValue) {
        if (getMetadata() == null || getMetadata().isEmpty()) {
            return defaultValue;
        }
        return getMetadata().get(key);
    }
    
}

package com.alibaba.nacos.api.naming.pojo.builder;

import com.alibaba.nacos.api.naming.pojo.Instance;

import java.util.HashMap;
import java.util.Map;
import java.util.Objects;

/**
 * Builder for {@link Instance}.
 *
 * @author xiweng.yy
 */
public class InstanceBuilder {
    
    private String instanceId;
    
    private String ip;
    
    private Integer port;
    
    private Double weight;
    
    private Boolean healthy;
    
    private Boolean enabled;
    
    private Boolean ephemeral;
    
    private String clusterName;
    
    private String serviceName;
    
    private Map<String, String> metadata = new HashMap<>();
    
    private InstanceBuilder() {
    }
    
    public InstanceBuilder setInstanceId(String instanceId) {
        this.instanceId = instanceId;
        return this;
    }
    
    public InstanceBuilder setIp(String ip) {
        this.ip = ip;
        return this;
    }
    
    public InstanceBuilder setPort(Integer port) {
        this.port = port;
        return this;
    }
    
    public InstanceBuilder setWeight(Double weight) {
        this.weight = weight;
        return this;
    }
    
    public InstanceBuilder setHealthy(Boolean healthy) {
        this.healthy = healthy;
        return this;
    }
    
    public InstanceBuilder setEnabled(Boolean enabled) {
        this.enabled = enabled;
        return this;
    }
    
    public InstanceBuilder setEphemeral(Boolean ephemeral) {
        this.ephemeral = ephemeral;
        return this;
    }
    
    public InstanceBuilder setClusterName(String clusterName) {
        this.clusterName = clusterName;
        return this;
    }
    
    public InstanceBuilder setServiceName(String serviceName) {
        this.serviceName = serviceName;
        return this;
    }
    
    public InstanceBuilder setMetadata(Map<String, String> metadata) {
        this.metadata = metadata;
        return this;
    }
    
    public InstanceBuilder addMetadata(String metaKey, String metaValue) {
        this.metadata.put(metaKey, metaValue);
        return this;
    }
    
    /**
     * Build a new {@link Instance}.
     *
     * @return new instance
     */
    public Instance build() {
        Instance result = new Instance();
        if (!Objects.isNull(instanceId)) {
            result.setInstanceId(instanceId);
        }
        if (!Objects.isNull(ip)) {
            result.setIp(ip);
        }
        if (!Objects.isNull(port)) {
            result.setPort(port);
        }
        if (!Objects.isNull(weight)) {
            result.setWeight(weight);
        }
        if (!Objects.isNull(healthy)) {
            result.setHealthy(healthy);
        }
        if (!Objects.isNull(enabled)) {
            result.setEnabled(enabled);
        }
        if (!Objects.isNull(ephemeral)) {
            result.setEphemeral(ephemeral);
        }
        if (!Objects.isNull(clusterName)) {
            result.setClusterName(clusterName);
        }
        if (!Objects.isNull(serviceName)) {
            result.setServiceName(serviceName);
        }
        result.setMetadata(metadata);
        return result;
    }
    
    public static InstanceBuilder newBuilder() {
        return new InstanceBuilder();
    }
}

使用方式如下:

// 构造器方式.
Instance instance = InstanceBuilder.newBuilder().setInstanceId(XXX).build();

4、Nacos的缓存构造器

package com.alibaba.nacos.common.cache.builder;

import com.alibaba.nacos.common.cache.Cache;
import com.alibaba.nacos.common.cache.decorators.AutoExpireCache;
import com.alibaba.nacos.common.cache.decorators.LruCache;
import com.alibaba.nacos.common.cache.decorators.SynchronizedCache;
import com.alibaba.nacos.common.cache.impl.SimpleCache;

import java.util.Objects;
import java.util.concurrent.TimeUnit;

/**
 * Cache builder.
 * @author zzq
 * @date 2021/7/30
 */
public class CacheBuilder<K, V> {
    
    private static final int DEFAULT_MAXIMUMSIZE = 1024;
    
    private static final int DEFAULT_INITIALIZE_CAPACITY = 1024;
    
    private static final int DEFAULT_EXPIRE_NANOS = -1;
    
    private long expireNanos = DEFAULT_EXPIRE_NANOS;
    
    private int maximumSize = DEFAULT_MAXIMUMSIZE;
    
    private int initializeCapacity = DEFAULT_INITIALIZE_CAPACITY;
    
    private boolean sync = false;
    
    private boolean lru = false;
    
    public static <K, V> CacheBuilder<K, V> builder() {
        return new CacheBuilder<>();
    }
    
    /**
     * Set expiration time.
     */
    public CacheBuilder<K, V> expireNanos(long duration, TimeUnit unit) {
        checkExpireNanos(duration, unit);
        this.expireNanos = unit.toNanos(duration);
        return this;
    }
    
    private void checkExpireNanos(long duration, TimeUnit unit) {
        if (duration < 0) {
            throw new IllegalArgumentException("duration cannot be negative");
        }
        if (Objects.isNull(unit)) {
            throw new IllegalArgumentException("unit cannot be null");
        }
    }
    
    /**
     * Set the maximum capacity of the cache pair.
     * @param maximumSize maximum capacity
     */
    public CacheBuilder<K, V> maximumSize(int maximumSize) {
        if (maximumSize < 0) {
            throw new IllegalArgumentException("size cannot be negative");
        }
        this.maximumSize = maximumSize;
        return this;
    }
    
    /**
     * Set whether the cache method is synchronized.
     * @param sync if sync value is true, each method of the constructed cache is synchronized.
     */
    public CacheBuilder<K, V> sync(boolean sync) {
        this.sync = sync;
        return this;
    }
    
    /**
     * Does the constructed cache support lru.
     * @param lru If the cache built for true is a