Java 为什么RESTAPI在嵌套对象上返回空JSON?
我正在尝试从Heroku应用程序数据库中检索给定电子邮件id的所有帖子 我有一个查询类,它处理所有请求(目前只处理Java 为什么RESTAPI在嵌套对象上返回空JSON?,java,json,rest,heroku,Java,Json,Rest,Heroku,我正在尝试从Heroku应用程序数据库中检索给定电子邮件id的所有帖子 我有一个查询类,它处理所有请求(目前只处理GET) 下面是Query.java import javax.ws.rs.GET; import javax.ws.rs.Path; import javax.ws.rs.Produces; import javax.ws.rs.core.MediaType; import com.auro.assignment.wallpostapi.model.PostBundle; @P
GET
)
下面是Query.java
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import com.auro.assignment.wallpostapi.model.PostBundle;
@Path("query")
public class Query {
public Query() {
}
@GET
@Produces(MediaType.APPLICATION_JSON)
public PostBundle getPostBundle() {
PostManager postManager = new PostManager();
return postManager.getPostBundle("xyz.123@test.in");
}
}
import java.io.PrintWriter;
import java.io.StringWriter;
import java.net.URISyntaxException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import com.auro.assignment.wallpostapi.dbconnection.DBConnectionManager;
import com.auro.assignment.wallpostapi.model.*;
public class PostManager {
private PostBundle postBundle;
private List<Post> posts;
public PostManager() {
postBundle = null;
posts = new ArrayList<>();
}
public PostBundle getPostBundle(final String email) {
try {
Connection connection = DBConnectionManager.getConnection();
final String query = "SELECT user_post, post_time FROM wall_post WHERE user_id = " +
"(SELECT user_id FROM user_info WHERE user_email = ?);";
PreparedStatement preparedStatement = connection.prepareStatement(query);
preparedStatement.setString(1, email);
ResultSet resultSet = preparedStatement.executeQuery();
if (resultSet != null && resultSet.next()) {
while (resultSet.next()) {
posts.add(new Post(resultSet.getString("user_post"),resultSet.getString("post_time")));
}
postBundle = new PostBundle("200","SUCCESS!",posts);
return postBundle;
}
else {
postBundle = new PostBundle("404","NOT FOUND",null);
return postBundle;
}
} catch (ClassNotFoundException | URISyntaxException | SQLException e) {
StringWriter stringWriter = new StringWriter();
PrintWriter printWriter = new PrintWriter(stringWriter);
e.printStackTrace(printWriter);
String stackTrace = stringWriter.toString();
postBundle = new PostBundle("500",stackTrace,null);
return postBundle;
}
}
}
Following is the **PostBundle.java**
import java.util.List;
public class PostBundle {
private String status;
private String message;
private List<Post> posts;
public PostBundle() {
status = null;
message = null;
posts = null;
}
public PostBundle(final String status, final String message, final List<Post> posts) {
this.status = status;
this.message = message;
this.posts = posts;
}
public String getStatus() {
return status;
}
public String getMessage() {
return message;
}
public List<Post> getPosts() {
return posts;
}
}
public class Post {
private String data;
private String date;
public Post() {
data = null;
date = null;
}
public Post(final String data, final String date) {
this.data = data;
this.date = date;
}
public String getData() {
return data;
}
public String getDate() {
return date;
}
}
然后我有一个名为PostManager的东西,它将所有帖子与状态码和消息捆绑在一起
以下是PostManager.java的
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import com.auro.assignment.wallpostapi.model.PostBundle;
@Path("query")
public class Query {
public Query() {
}
@GET
@Produces(MediaType.APPLICATION_JSON)
public PostBundle getPostBundle() {
PostManager postManager = new PostManager();
return postManager.getPostBundle("xyz.123@test.in");
}
}
import java.io.PrintWriter;
import java.io.StringWriter;
import java.net.URISyntaxException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import com.auro.assignment.wallpostapi.dbconnection.DBConnectionManager;
import com.auro.assignment.wallpostapi.model.*;
public class PostManager {
private PostBundle postBundle;
private List<Post> posts;
public PostManager() {
postBundle = null;
posts = new ArrayList<>();
}
public PostBundle getPostBundle(final String email) {
try {
Connection connection = DBConnectionManager.getConnection();
final String query = "SELECT user_post, post_time FROM wall_post WHERE user_id = " +
"(SELECT user_id FROM user_info WHERE user_email = ?);";
PreparedStatement preparedStatement = connection.prepareStatement(query);
preparedStatement.setString(1, email);
ResultSet resultSet = preparedStatement.executeQuery();
if (resultSet != null && resultSet.next()) {
while (resultSet.next()) {
posts.add(new Post(resultSet.getString("user_post"),resultSet.getString("post_time")));
}
postBundle = new PostBundle("200","SUCCESS!",posts);
return postBundle;
}
else {
postBundle = new PostBundle("404","NOT FOUND",null);
return postBundle;
}
} catch (ClassNotFoundException | URISyntaxException | SQLException e) {
StringWriter stringWriter = new StringWriter();
PrintWriter printWriter = new PrintWriter(stringWriter);
e.printStackTrace(printWriter);
String stackTrace = stringWriter.toString();
postBundle = new PostBundle("500",stackTrace,null);
return postBundle;
}
}
}
Following is the **PostBundle.java**
import java.util.List;
public class PostBundle {
private String status;
private String message;
private List<Post> posts;
public PostBundle() {
status = null;
message = null;
posts = null;
}
public PostBundle(final String status, final String message, final List<Post> posts) {
this.status = status;
this.message = message;
this.posts = posts;
}
public String getStatus() {
return status;
}
public String getMessage() {
return message;
}
public List<Post> getPosts() {
return posts;
}
}
public class Post {
private String data;
private String date;
public Post() {
data = null;
date = null;
}
public Post(final String data, final String date) {
this.data = data;
this.date = date;
}
public String getData() {
return data;
}
public String getDate() {
return date;
}
}
它在返回一个空的JSON
我的架构设计有什么问题吗?我猜可能发生了某种内部错误,但在PostManager方法中,我确保任何错误stacktrace也被捆绑,但我得到的是一个完全空白的屏幕。我在这里看到一些错误: 首先,调用
resultSet.next()
两次
// Initially the cursor is positioned before the first row.
ResultSet resultSet = preparedStatement.executeQuery();
if (resultSet != null && resultSet.next()) { // The cursor is moved to the first row
while (resultSet.next()) { // The cursor is moved to the second row, so you skipped the
// first result and it only iterates from second to last one
...
}
postBundle = new PostBundle("200","SUCCESS!",posts); // posts only contains from
//second to last result. In case
//you only have one result,
//posts is an empty ArrayList
return postBundle;
}
“xyz”有多少个帖子。123@test.in“你有吗?如果只有一个,那就是问题所在
Second,preparedStatement.executeQuery()
从不返回null
因此,您不需要检查它是否为null
第三,如果电子邮件中没有任何帖子,则永远不要返回404,而应返回200,其中包含空json。
200确定-请求已成功。返回的信息与
响应取决于请求中使用的方法
404未找到-服务器未找到任何与
请求URI
404错误保留用于请求URI匹配
最后,您应该相应地修改代码:
您应该修改以下代码:
...
try {
Connection connection = DBConnectionManager.getConnection();
final String query = "SELECT user_post, post_time FROM wall_post WHERE user_id = " +
"(SELECT user_id FROM user_info WHERE user_email = ?);";
PreparedStatement preparedStatement = connection.prepareStatement(query);
preparedStatement.setString(1, email);
ResultSet resultSet = preparedStatement.executeQuery();
while (resultSet.next()) {
posts.add(new Post(resultSet.getString("user_post"),resultSet.getString("post_time")));
}
postBundle = new PostBundle("200","SUCCESS!",posts);
return postBundle;
}
...
我在这里看到一些错误: 首先,调用
resultSet.next()
两次
// Initially the cursor is positioned before the first row.
ResultSet resultSet = preparedStatement.executeQuery();
if (resultSet != null && resultSet.next()) { // The cursor is moved to the first row
while (resultSet.next()) { // The cursor is moved to the second row, so you skipped the
// first result and it only iterates from second to last one
...
}
postBundle = new PostBundle("200","SUCCESS!",posts); // posts only contains from
//second to last result. In case
//you only have one result,
//posts is an empty ArrayList
return postBundle;
}
“xyz”有多少个帖子。123@test.in“你有吗?如果只有一个,那就是问题所在
Second,preparedStatement.executeQuery()
从不返回null
因此,您不需要检查它是否为null
第三,如果电子邮件中没有任何帖子,则永远不要返回404,而应返回200,其中包含空json。
200确定-请求已成功。返回的信息与
响应取决于请求中使用的方法
404未找到-服务器未找到任何与
请求URI
404错误保留用于请求URI匹配
最后,您应该相应地修改代码:
您应该修改以下代码:
...
try {
Connection connection = DBConnectionManager.getConnection();
final String query = "SELECT user_post, post_time FROM wall_post WHERE user_id = " +
"(SELECT user_id FROM user_info WHERE user_email = ?);";
PreparedStatement preparedStatement = connection.prepareStatement(query);
preparedStatement.setString(1, email);
ResultSet resultSet = preparedStatement.executeQuery();
while (resultSet.next()) {
posts.add(new Post(resultSet.getString("user_post"),resultSet.getString("post_time")));
}
postBundle = new PostBundle("200","SUCCESS!",posts);
return postBundle;
}
...
建议的解决方案对您有效吗?如果是,你能接受这个解决方案吗?如果没有,你能告诉我们什么仍然不起作用吗?建议的解决方案对你有效吗?如果是,你能接受这个解决方案吗?如果没有,你能告诉我们什么仍然不起作用吗?