目录
- 使用场景
- 实现
实现 假如现在有个pdf的配置类其中有尺寸、标题、作者、颜色等字段，其中作者和颜色是可以不传入的但是尺寸和标题是必须传入的，并且尺寸是有枚举值的，那么可以进行以下实现。
public class PdfConfig {
public static final String A3 = "A3";
public static final String A4 = "A4";
/**
* 尺寸
*/
private final String specification;
/**
* 标题
*/
private final String title;
/**
* 作者
*/
private final String author;
/**
* 颜色
*/
private String color;
private PdfConfig(Builder builder) {
this.specification = builder.specification;
this.title = builder.title;
this.author = builder.author;
this.color = builder.color;
}@Override
public String toString() {
return "PdfConfig{" +
"specification='" + specification + '\'' +
", title='" + title + '\'' +
", author='" + author + '\'' +
", color='" + color + '\'' +
'}';
}public static class Builder{private String specification;
private String title;
private String author;
private String color;
public Builder setSpecification(String sf){
this.specification = sf;
return this;
}public Builder setTitle(String title){
this.title = title;
return this;
}public Builder setAuthor(String author){
this.author = author;
return this;
}public Builder setColor(String color){
this.color = color;
return this;
}public PdfConfig build(){
if (!A3.equals(specification) && !A4.equals(specification)){
throw new RuntimeException("尺寸不合规");
}else if (title == null){
throw new RuntimeException("请输入标题");
}
return new PdfConfig(this);
}
}
}下面是其使用过程，这样就相比不断地使用对象进行set或者使用构造函数传入固定参数而言，"优雅得多"
public class PdfConfigDemo {
public static void main(String[] args) {
PdfConfig pdfConfig = new PdfConfig.Builder()
.setSpecification(PdfConfig.A3)
.setAuthor("eacape")
.setTitle("hello")
.build();
System.out.printf(pdfConfig.toString());
}
}
【建造者模式】在一些中间件和java api中，建造者模式还是比较常见的，例如lombok的
@Builder和StringBuilder类
