前言

构建者模式，是用来构建我们的对象。如果我们构建的对象有很多属性值要设置，使用大量的setXX()，这样代码不利于阅读，也不整洁。

实现

我们假设有创建的是一个订单。使用构建者模式如下。PS:通常的构建者模式中是不提供setXX()方法，一旦对象构建以后就不允许修改，但是实际业务场景中有时候创建完一个对象，后续根据情形需要单独修改某个属性值，所以提供了setXX().

/**
  * 订单
 */
public class Order {
/**
 * 价格
 */
private Double price;
/**
 * 订单号
 */
private String orderId;
/**
 * 寄件人姓名
 */
private String sendMan;
/**
 * 寄件人地址
 */
private String sendAddress;
/**
 * 寄件人电话
 */
private String sendMobile;
/**
 * 收件人
 */
private String receiveMan;
/**
 * 收件人地址
 */
private String receiveAddress;
/**
 * 收件人电话
 */
private String receiveMobile;
/**
 * 备注
 */
private String remark;

public Double getPrice() {
    return price;
}

public void setPrice(Double price) {
    this.price = price;
}

public String getOrderId() {
    return orderId;
}

public void setOrderId(String orderId) {
    this.orderId = orderId;
}

public String getSendMan() {
    return sendMan;
}

public void setSendMan(String sendMan) {
    this.sendMan = sendMan;
}

public String getSendAddress() {
    return sendAddress;
}

public void setSendAddress(String sendAddress) {
    this.sendAddress = sendAddress;
}

public String getSendMobile() {
    return sendMobile;
}

public void setSendMobile(String sendMobile) {
    this.sendMobile = sendMobile;
}

public String getReceiveMan() {
    return receiveMan;
}

public void setReceiveMan(String receiveMan) {
    this.receiveMan = receiveMan;
}

public String getReceiveAddress() {
    return receiveAddress;
}

public void setReceiveAddress(String receiveAddress) {
    this.receiveAddress = receiveAddress;
}

public String getReceiveMobile() {
    return receiveMobile;
}

public void setReceiveMobile(String receiveMobile) {
    this.receiveMobile = receiveMobile;
}

public String getRemark() {
    return remark;
}

public void setRemark(String remark) {
    this.remark = remark;
}
/**
 * 静态方法获取bulider
 * @return
 */
public static Builder Builder(){
    return new Builder();
}
  /**
 * Builder是public static 内部类.
 * 1 pulblic 为了扩大访问域，包外也可以
 * 2 static 是为了Order方法需要通过静态方法获取Builder
 */
public static class Builder{
    private Double price;
    private String orderId;
    private String sendMan;
    private String sendAddress;
    private String sendMobile;
    private String receiveMan;
    private String receiveAddress;
    private String receiveMobile;
    private String remark;
    public Builder price(Double price){
        this.price = price;
        return this;
    }
    public Builder orderId(String orderId){
        this.orderId = orderId;
        return this;
    }
    public Builder sendMan(String sendMan){
        this.sendMan = sendMan;
        return this;
    }
    public Builder sendAddress(String sendAddress){
        this.sendAddress = sendAddress;
        return this;
    }
    public Builder sendMobile(String sendMobile){
        this.sendMobile = sendMobile;
        return this;
    }
    public Builder receiveMan(String receiveMan){
        this.receiveMan = receiveMan;
        return this;
    }
    public Builder receiveAddress(String receiveAddress){
        this.receiveAddress = receiveAddress;
        return this;
    }

    public Builder receiveMobile(String receiveMobile){
        this.receiveMobile = receiveMobile;
        return this;
    }
    public Builder remark(String remark){
        this.remark = remark;
        return this;
    }
    public Order build(){
        Order order = new Order();
        order.orderId = this.orderId;
        order.price = this.price;
        order.receiveAddress = this.receiveAddress;
        order.receiveMan = this.receiveMan;
        order.receiveMobile = this.receiveMobile;
        order.price = this.price;
        order.sendAddress = this.sendAddress;
        order.sendMan = this.sendMan;
        order.sendMobile = this.sendMobile;
        order.remark = this.remark;
        return order;
        
    }

}
}

使用方式：

public class DesignPatternApplication {
public static void main(String[] args) {
    Order order = Order.Builder().orderId("123").price(12.4).receiveMan("dd")
            .receiveAddress("dd").sendAddress("dd").remark("ddada").build();
    //后续业务场景需要，可以修改某个属性
    order.setRemark("666");
    System.out.println(order.getOrderId());
}
}

不重复造轮子，使用lombok

复杂的系统中，为了开发人员更专注于业务，不必要编写AllArgsConstructor，NoArgsConstructor,Builder，getter,setter，建议使用lombok。通过简单的注解，即可完成以上重复繁琐的工作，引入lombok后编译器在编译的时候会生成包含以上内容class文件，感兴趣的小伙伴可以看看引入lombok后生成的class文件