solr通过javabean添加索引出错

Question

错误信息：Bad Request

request: http://localhost:8080/solr/update?wt=javabin&version=2
索引的字段：
field.setBook_id(book.getId());
field.setBook_name(book.getName());
field.setBook_author(book.getAuthor());
field.setBook_content(book.getContent());
schema.xml文件字段定义：

javabean字段，set方法也用注解@Field("book_name") 等对应了
private String book_id;
private String book_name;
private String book_content;
private String book_author;

还有什么原因啊，帮帮忙！