java-Builder模式简单示例

package com.ctid.dnc.business.hcode.model;

public class RedisError {

    /**
     * 业务类型
     */
    public final String businessType;
    /**
     * 执行类名
     */
    public final String className;
    /**
     * 执行方法
     */
    public final String method;
    /**
     * 操作描述
     */
    public final String operations;
    /**
     * 异常描述
     */
    public final String summary;
    

    public RedisError() {
        this(new Builder());
    }

    public RedisError(Builder builder){
        this.businessType = builder.businessType;
        this.className = builder.className;
        this.method = builder.method;
        this.operations = builder.operations;
        this.summary = builder.summary;
    }



    @Override
    public String toString() {
        return "异常信息为：{" +
                "业务类型：'" + businessType + '\'' +
                ", 执行类名：'" + className + '\'' +
                ", 执行方法：'" + method + '\'' +
                ", 操作描述：'" + operations + '\'' +
                ", 异常描述：'" + summary + '\'' +
                '}';
    }


    /**
     *静态内部类 Builder
     */
    public static class Builder {
        public String businessType;
        public String className;
        public String method;
        public String operations;
        public String summary;

        public Builder() {
        }

        Builder(RedisError redisError) {
            this.businessType = redisError.businessType;
            this.className = redisError.className;
            this.method = redisError.method;
            this.operations = redisError.operations;
            this.summary = redisError.summary;
        }

        public Builder setBusinessType(String businessType) {
            this.businessType = businessType;
            return this;
        }

        public Builder setClassName(String className) {
            this.className = className;
            return this;
        }

        public Builder setMethod(String method) {
            this.method = method;
            return this;
        }

        public Builder setOperations(String operations) {
            this.operations = operations;
            return this;
        }

        public Builder setSummary(String summary) {
            this.summary = summary;
            return this;
        }

        //构建一个实体
        public RedisError build() {
            return new RedisError(this);
        }
    }

}

其实也不需要建内部类，简单的话在实体类set方法中把返回值改为返回实体对象本身就行。