mongo判断某些字段上有没有索引，进行动态创建

IndexOptions:
 private boolean background;
    private boolean unique;
    private String name;
    private boolean sparse;
    private Long expireAfterSeconds;
    private Integer version;
    private Bson weights;
    private String defaultLanguage;
    private String languageOverride;
    private Integer textVersion;
    private Integer sphereVersion;
    private Integer bits;
    private Double min;
    private Double max;
    private Double bucketSize;
    private Bson storageEngine;
    private Bson partialFilterExpression;
    private Collation collation;
    private Bson wildcardProjection;
    private boolean hidden;

        IndexOperations animals = mongoTemplate.indexOps("animals");
        List<IndexInfo> indexInfo = animals.getIndexInfo();
        for (IndexInfo index:indexInfo){
            List<IndexField> indexFields = index.getIndexFields();
            //索引名称
            String name = index.getName();
            for (IndexField indexField : indexFields) {
                //有索引的字段
                String key = indexField.getKey();
                //索引所在的字段不为空，并且与我们想要的目标字段不相等
                if(Objects.isNull(key)&&key.equals("目标字段")){
                    //在这里给目标字段设置索引 然后跳出循环即可
                    /**
                     *   IndexOptions indexOptions = new IndexOptions();
                     *                     //后台创建索引
                     *                     indexOptions.background(true);
                     *                     //唯一索引
                     * //                    indexOptions.unique(true);
                     *                     //如果为true，则索引仅引用具有指定字段的文档
                     * //                    indexOptions.sparse(true);
                     *                     mongoTemplate.createCollection("animals")
                     *                             .createIndex(Indexes.ascending("name"),
                     *                                     indexOptions);
                     */
                    break;
                }
            }
//            Optional<Document> collation = index.getCollation();

        }