这里我想从多个表中收集多行，所以我想将值设置为 beans.in user.java 有一个 Set<UserRole>所以我也想为该字段设置。所以我也为此编写了另一个行映射器。因此，为了避免设置这些字段，是否有其他方法来设置它们。
User.java
公共(public)类 User 实现可序列化{
private Integer id;
private String username;
private String password;
private Set<UserRole> userRoles = new HashSet<UserRole>(0);
public User() {
}
UserRole.java
public class UserRole implements Serializable{
private Integer id;
private User user;
private Role role;
public UserRole() {
}
角色.java
public class Role implements Serializable{
private Integer roleId;
private String roleName;
private Set<UserRole> userRoles = new HashSet<UserRole>(0);
private Set<RoleAction> roleActions = new HashSet<RoleAction>(0);
Action.java
public class Action implements Serializable{
private Integer id;
private String name;
private Set<RoleAction> roleActions = new HashSet<RoleAction>(0);
Dao.java
public User getUser(String username){
List<User> userModelList=new ArrayList<User>();
try{
String query="select ID,USERNAME,PASSWORD from users u where u.username = ?";
userModelList = jdbcTemplate.query(query, new Object[] { username },
new RowMapper<User>(){
@Override
public User mapRow( ResultSet resultSet, int rownumber)
throws SQLException {
User user=new User();
user.setId(resultSet.getInt("ID"));
user.setUsername(resultSet.getString("USERNAME"));
user.setPassword(resultSet.getString("PASSWORD"));
int userid=user.getId();
Role role=roleasd(userid);
Set<UserRole> userRoles=setUserRole(role,user);
for(UserRole ur:userRoles){
System.out.println("userRole details "+ur.getId()+""+ur.getRole().getRoleActions());
}
user.setUserRoles(userRoles);
System.out.println("the values are "+user.getId()+" " +user.getUsername());
return user;
}
private Set<UserRole> setUserRole(Role role, User user) {
Integer id = user.getId();
System.out.println("coming to setuserrole id is "+ id);
String query = "select * from user_role where USER_ID=? ";
Set<UserRole> userRoles = new HashSet<UserRole>();
jdbcTemplate.query(query, new Object[] { id },
new RowMapper<UserRole>() {
@Override
public UserRole mapRow(ResultSet rs, int arg1)
throws SQLException {
UserRole userRole=new UserRole();
System.out.println("**********"+rs.getInt("ID"));
userRole.setId(rs.getInt("ID"));
userRole.setRole(role);
userRole.setUser(user);
userRoles.add(userRole);
return userRole;
}
});
System.out.println("Size::::"+userRoles.size());
return userRoles;
}
public Role roleasd(int userid) {
String query="select * from role where ROLE_ID = ?";
Role role=new Role();
jdbcTemplate.query(query, new Object[] { userid },new RowMapper<Role>(){
@Override
public Role mapRow(ResultSet rs, int arg1)
throws SQLException {
role.setRoleId(rs.getInt("ROLE_ID"));
role.setRoleName(rs.getString("ROLE_NAME"));
System.out.println(":::"+rs.getString("ROLE_NAME"));
return role;
}
});
return role;
}
});
}catch(Exception e){
System.out.println(" the DB error is "+e.getMessage());
}
if (userModelList.size()>0) {
System.out.println("the list is "+ userModelList.get(0).getUserRoles());
return userModelList.get(0);
}
return null;
}
最佳答案
根据建议，您应该使用 JOIN 查询。但是，仍然存在返回两种不同类型的对象的问题，而一个 RowMapper 只返回一种对象。一种解决方案是使用一个包装器对象来封装两者:
public class Result{
private final User user;
private final Role role;
public Result(User user, Role role){
this.role=role; this.user = user;
}
/* getters here */
}
现在你可以像这样构建 RowMapper:
List<Result> resultList = jdbcQuery.query(/* some sql */,
(rs, arg1) ->{ // RowMapper as Lambda
User user = new User();
// assign user properties from rs
Role role = new Role();
// assign role properties from rs;
return new Result(user, role);
});
// now process your users and roles
resultList.forEach(r -> {
User user = result.getUser();
Role role = result.getRole();
// do something here with User and Role
});
关于java - 如何在spring jdbctemplate中从多个表中选择多行，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40255812/