Mybatis选择带有嵌套对象 [英] Mybatis select with nested objects

问题描述

我正在使用MyBatis进行简单选择.

I am using MyBatis to do a simple select.

假设我们有以下课程:

class Book {
    private String bookName;

    public Book(String bookName){
        this.bookName = bookName;
    }

    public String getBookName(){
        return bookName;
    }
}


class Student {
    private String studentName;
    private Book book;

    public Student(){}

    // getters and setters
}

我在返回Student对象的方法上具有注释.

I have an annotation on a method that returns a Student object.

@Select("Select studentName, book from Students")

我的问题是这本书总是空的.我假设MyBatis将使用该JDBC类型(在这种情况下为String)调用构造函数来填充书籍.我缺少什么或做错了什么?

My Issue is that book is always null. I was under the assumption MyBatis will call the constructor with that JDBC type (in this case String) to populate book. What am I missing or doing incorrectly?

推荐答案

一个选项是

使用@ConstructorArgs批注显式调用Constructor方法.

Use @ConstructorArgs annotations to explicitly call Constructor method.

@Select("Select studentName, book from Students")
@ConstructorArgs(value = { 
@Arg(column = "studentName", javaType=java.lang.String.class),
@Arg(column = "book", javaType = java.lang.String.class)
})

并将其传递给Student构造函数，该构造函数将调用Book构造函数.

and pass them to Student constructor, which calls Book constructor.

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