Optional columns to filter dataBase records

问题

How should I use the finder of Ebean to create a query with optional columns to filter some data?

I want to get a List<User> for instance. Imagine I have 3 columns to filter: by Name, by genre and something else. If I select the genre, the query should list all records of genre selected, after that, if I select name John and genre male, the query should List all "John" who are "male" and it's so on.

I know to create simple querys to find for a column:

find.where().eq("ex1",var1).eq("ex2", var2).findList();

Any suggestion ?

回答1:

Try using ExpressionList. Here is the sample, if the conditions in the if statement met, then the expression will be included on the where clause.

public static List<User> filterUsers(int user_no, String genre, String name){

    com.avaje.ebean.ExpressionList expressionList = find.where().eq("user_no", user_no);

    if(condition1)
        expressionList.eq("genre", genre);

    if(condition2)
        expressionList.eq("name", name);

    return expressionList.findList();

}

来源：https://stackoverflow.com/questions/31534272/optional-columns-to-filter-database-records