/*@jsxRuntime automatic @jsxImportSource react*/
const {Fragment: _Fragment, jsx: _jsx, jsxs: _jsxs} = arguments[0];
function _createMdxContent(props) {
  const _components = Object.assign({
    p: "p",
    a: "a",
    code: "code",
    pre: "pre",
    span: "span",
    h2: "h2",
    ol: "ol",
    li: "li"
  }, props.components), {Link} = _components;
  if (!Link) _missingMdxReference("Link", true);
  return _jsxs(_Fragment, {
    children: [_jsxs(_components.p, {
      children: ["In ", _jsx(Link, {
        href: "/blog/the-rss-reader-tutorial/",
        passHref: true,
        children: _jsx(_components.a, {
          href: "",
          children: "the pre­vi­ous step"
        })
      }), ", we have suc­cess­fully im­ple­mented the first end­point\nof the RSS reader app."]
    }), "\n", _jsxs(_components.p, {
      children: ["The RSS reader ex­am­ple as­sumes im­ple­ment­ing 3 end­points. This ar­ti­cle is ded­i­cated to im­ple­ment­ing the ", _jsx(_components.code, {
        children: "GET /user/{user_id}/rss_channels"
      }), " end­point."]
    }), "\n", _jsxs(_components.p, {
      children: ["Be­fore com­plet­ing this step, make sure your are in the ", _jsx(_components.code, {
        children: "step_2"
      }), " git branch:"]
    }), "\n", _jsx(_components.pre, {
      children: _jsxs(_components.code, {
        className: "hljs language-better-shell",
        children: [_jsx(_components.span, {
          className: "hljs-meta",
          children: "$"
        }), _jsx(_components.span, {
          className: "bash",
          children: " git checkout step_2"
        }), "\n"]
      })
    }), "\n", _jsxs(_components.h2, {
      id: "implementing-the-second-endpoint",
      children: [_jsx(_components.a, {
        "aria-hidden": true,
        tabIndex: "-1",
        className: "heading-anchor",
        href: "#implementing-the-second-endpoint"
      }), "Implementing the second endpoint"]
    }), "\n", _jsxs(_components.p, {
      children: ["The sec­ond end­point pro­duces an array of RSS chan­nels by given ", _jsx(_components.code, {
        children: "user_id"
      }), "."]
    }), "\n", _jsx(_components.p, {
      children: "We need to ex­e­cute the two fol­low­ing queries to:"
    }), "\n", _jsxs(_components.ol, {
      children: ["\n", _jsxs(_components.li, {
        children: ["Fetch RSS links for a given user:", "\n", _jsx(_components.pre, {
          children: _jsxs(_components.code, {
            className: "hljs language-sql",
            children: [_jsx(_components.span, {
              className: "hljs-keyword",
              children: "SELECT"
            }), " rss_link ", _jsx(_components.span, {
              className: "hljs-keyword",
              children: "FROM"
            }), " rss_by_user ", _jsx(_components.span, {
              className: "hljs-keyword",
              children: "WHERE"
            }), " login ", _jsx(_components.span, {
              className: "hljs-operator",
              children: "="
            }), " GIVEN_USER_ID ;\n"]
          })
        }), "\n"]
      }), "\n", _jsxs(_components.li, {
        children: ["Fetch RSS chan­nel de­tails for a given link:", "\n", _jsx(_components.pre, {
          children: _jsxs(_components.code, {
            className: "hljs language-sql",
            children: [_jsx(_components.span, {
              className: "hljs-keyword",
              children: "SELECT"
            }), " description, title, site_link, rss_link ", _jsx(_components.span, {
              className: "hljs-keyword",
              children: "FROM"
            }), " channel_info_by_rss_link ", _jsx(_components.span, {
              className: "hljs-keyword",
              children: "WHERE"
            }), " rss_link ", _jsx(_components.span, {
              className: "hljs-operator",
              children: "="
            }), " GIVEN_LINK ;\n"]
          })
        }), "\n"]
      }), "\n"]
    }), "\n", _jsxs(_components.h2, {
      id: "implementation",
      children: [_jsx(_components.a, {
        "aria-hidden": true,
        tabIndex: "-1",
        className: "heading-anchor",
        href: "#implementation"
      }), "Implementation"]
    }), "\n", _jsxs(_components.p, {
      children: ["The end­point al­lows the the front-​end app to dis­play the list of RSS feeds a user sub­scribed on. When the end­point is ac­cessed, the ", _jsx(_components.code, {
        children: "AppVerticle#getRssChannels"
      }), " method is called. We can im­ple­ment this method in this way:"]
    }), "\n", _jsx(_components.pre, {
      children: _jsxs(_components.code, {
        className: "hljs language-java",
        children: [_jsx(_components.span, {
          className: "hljs-keyword",
          children: "private"
        }), " ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "void"
        }), " ", _jsx(_components.span, {
          className: "hljs-title function_",
          children: "getRssChannels"
        }), _jsx(_components.span, {
          className: "hljs-params",
          children: "(RoutingContext ctx)"
        }), " {\n    ", _jsx(_components.span, {
          className: "hljs-type",
          children: "String"
        }), " ", _jsx(_components.span, {
          className: "hljs-variable",
          children: "userId"
        }), " ", _jsx(_components.span, {
          className: "hljs-operator",
          children: "="
        }), " ctx.request().getParam(", _jsx(_components.span, {
          className: "hljs-string",
          children: "\"user_id\""
        }), ");\n    ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "if"
        }), " (userId == ", _jsx(_components.span, {
          className: "hljs-literal",
          children: "null"
        }), ") {\n        responseWithInvalidRequest(ctx);\n    } ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "else"
        }), " {\n        Future<List<Row>> future = Future.future();\n        client.executeWithFullFetch(selectRssLinksByLogin.bind(userId), future);\n        future.compose(rows -> {\n            List<String> links = rows.stream()\n                    .map(row -> row.getString(", _jsx(_components.span, {
          className: "hljs-number",
          children: "0"
        }), "))\n                    .collect(Collectors.toList());\n\n            ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "return"
        }), " CompositeFuture.all(\n                    links.stream().map(selectChannelInfo::bind).map(statement -> {\n                        Future<List<Row>> channelInfoRow = Future.future();\n                        client.executeWithFullFetch(statement, channelInfoRow);\n                        ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "return"
        }), " channelInfoRow;\n                    }).collect(Collectors.toList())\n            );\n        }).setHandler(h -> {\n            ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "if"
        }), " (h.succeeded()) {\n                ", _jsx(_components.span, {
          className: "hljs-type",
          children: "CompositeFuture"
        }), " ", _jsx(_components.span, {
          className: "hljs-variable",
          children: "result"
        }), " ", _jsx(_components.span, {
          className: "hljs-operator",
          children: "="
        }), " h.result();\n                List<List<Row>> results = result.list();\n                List<Row> list = results.stream()\n                        .flatMap(List::stream)\n                        .collect(Collectors.toList());\n                ", _jsx(_components.span, {
          className: "hljs-type",
          children: "JsonObject"
        }), " ", _jsx(_components.span, {
          className: "hljs-variable",
          children: "responseJson"
        }), " ", _jsx(_components.span, {
          className: "hljs-operator",
          children: "="
        }), " ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "new"
        }), " ", _jsx(_components.span, {
          className: "hljs-title class_",
          children: "JsonObject"
        }), "();\n                ", _jsx(_components.span, {
          className: "hljs-type",
          children: "JsonArray"
        }), " ", _jsx(_components.span, {
          className: "hljs-variable",
          children: "channels"
        }), " ", _jsx(_components.span, {
          className: "hljs-operator",
          children: "="
        }), " ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "new"
        }), " ", _jsx(_components.span, {
          className: "hljs-title class_",
          children: "JsonArray"
        }), "();\n\n                list.forEach(eachRow -> channels.add(\n                        ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "new"
        }), " ", _jsx(_components.span, {
          className: "hljs-title class_",
          children: "JsonObject"
        }), "()\n                                .put(", _jsx(_components.span, {
          className: "hljs-string",
          children: "\"description\""
        }), ", eachRow.getString(", _jsx(_components.span, {
          className: "hljs-number",
          children: "0"
        }), "))\n                                .put(", _jsx(_components.span, {
          className: "hljs-string",
          children: "\"title\""
        }), ", eachRow.getString(", _jsx(_components.span, {
          className: "hljs-number",
          children: "1"
        }), "))\n                                .put(", _jsx(_components.span, {
          className: "hljs-string",
          children: "\"link\""
        }), ", eachRow.getString(", _jsx(_components.span, {
          className: "hljs-number",
          children: "2"
        }), "))\n                                .put(", _jsx(_components.span, {
          className: "hljs-string",
          children: "\"rss_link\""
        }), ", eachRow.getString(", _jsx(_components.span, {
          className: "hljs-number",
          children: "3"
        }), "))\n                ));\n\n                responseJson.put(", _jsx(_components.span, {
          className: "hljs-string",
          children: "\"channels\""
        }), ", channels);\n                ctx.response().end(responseJson.toString());\n            } ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "else"
        }), " {\n                log.error(", _jsx(_components.span, {
          className: "hljs-string",
          children: "\"failed to get rss channels\""
        }), ", h.cause());\n                ctx.response().setStatusCode(", _jsx(_components.span, {
          className: "hljs-number",
          children: "500"
        }), ").end(", _jsx(_components.span, {
          className: "hljs-string",
          children: "\"Unable to retrieve the info from C*\""
        }), ");\n            }\n        });\n    }\n}\n"]
      })
    }), "\n", _jsxs(_components.p, {
      children: ["Also, this method uses ", _jsx(_components.code, {
        children: "selectChannelInfo"
      }), " and ", _jsx(_components.code, {
        children: "selectRssLinksByLogin"
      }), " fields, they should be ini­tial­ized in the ", _jsx(_components.code, {
        children: "AppVerticle#prepareNecessaryQueries"
      }), " method:"]
    }), "\n", _jsx(_components.pre, {
      children: _jsxs(_components.code, {
        className: "hljs language-java",
        children: [_jsx(_components.span, {
          className: "hljs-keyword",
          children: "private"
        }), " Future<Void> ", _jsx(_components.span, {
          className: "hljs-title function_",
          children: "prepareNecessaryQueries"
        }), _jsx(_components.span, {
          className: "hljs-params",
          children: "()"
        }), " {\n    Future<PreparedStatement> selectChannelInfoPrepFuture = Future.future();\n    client.prepare(", _jsx(_components.span, {
          className: "hljs-string",
          children: "\"SELECT description, title, site_link, rss_link FROM channel_info_by_rss_link WHERE rss_link = ? ;\""
        }), ", selectChannelInfoPrepFuture);\n\n    Future<PreparedStatement> selectRssLinkByLoginPrepFuture = Future.future();\n    client.prepare(", _jsx(_components.span, {
          className: "hljs-string",
          children: "\"SELECT rss_link FROM rss_by_user WHERE login = ? ;\""
        }), ", selectRssLinkByLoginPrepFuture);\n\n    Future<PreparedStatement> insertNewLinkForUserPrepFuture = Future.future();\n    client.prepare(", _jsx(_components.span, {
          className: "hljs-string",
          children: "\"INSERT INTO rss_by_user (login , rss_link ) VALUES ( ?, ?);\""
        }), ", insertNewLinkForUserPrepFuture);\n\n    ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "return"
        }), " CompositeFuture.all(\n            selectChannelInfoPrepFuture.compose(preparedStatement -> {\n                selectChannelInfo = preparedStatement;\n                ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "return"
        }), " Future.succeededFuture();\n            }),\n            selectRssLinkByLoginPrepFuture.compose(preparedStatement -> {\n                selectRssLinksByLogin = preparedStatement;\n                ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "return"
        }), " Future.succeededFuture();\n            }),\n            insertNewLinkForUserPrepFuture.compose(preparedStatement -> {\n                insertNewLinkForUser = preparedStatement;\n                ", _jsx(_components.span, {
          className: "hljs-keyword",
          children: "return"
        }), " Future.succeededFuture();\n            })\n    ).mapEmpty();\n}\n"]
      })
    }), "\n", _jsxs(_components.h2, {
      id: "conclusion",
      children: [_jsx(_components.a, {
        "aria-hidden": true,
        tabIndex: "-1",
        className: "heading-anchor",
        href: "#conclusion"
      }), "Conclusion"]
    }), "\n", _jsxs(_components.p, {
      children: ["In this part, we have suc­cess­fully im­ple­mented the sec­ond end­point, which al­lows the browser app to ob­tain chan­nels in­for­ma­tion for a spe­cific user. To en­sure that it is work­ing fine, point your browser to ", _jsx(_components.code, {
        children: "localhost:8080"
      }), " and click to the re­fresh but­ton. Chan­nel list should ap­pear im­me­di­ately."]
    }), "\n", _jsxs(_components.p, {
      children: ["If you have any prob­lems with com­plet­ing this step you can check­out to ", _jsx(_components.code, {
        children: "step_3"
      }), ", where you can find all changes made for com­plet­ing this step:"]
    }), "\n", _jsx(_components.pre, {
      children: _jsxs(_components.code, {
        className: "hljs language-better-shell",
        children: [_jsx(_components.span, {
          className: "hljs-meta",
          children: "$"
        }), _jsx(_components.span, {
          className: "bash",
          children: " git checkout step_3"
        }), "\n"]
      })
    }), "\n", _jsxs(_components.p, {
      children: ["Thanks for read­ing this. I hope you en­joyed read­ing this ar­ti­cle. See you soon on our ", _jsx(_components.a, {
        href: "https://gitter.im/eclipse-vertx/vertx-users",
        children: "Git­ter chan­nel"
      }), "!"]
    })]
  });
}
function MDXContent(props = {}) {
  const {wrapper: MDXLayout} = props.components || ({});
  return MDXLayout ? _jsx(MDXLayout, Object.assign({}, props, {
    children: _jsx(_createMdxContent, props)
  })) : _createMdxContent(props);
}
return {
  default: MDXContent
};
function _missingMdxReference(id, component) {
  throw new Error("Expected " + (component ? "component" : "object") + " `" + id + "` to be defined: you likely forgot to import, pass, or provide it.");
}


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