使用JDBC CallableStatements執行存儲過程

使用JDBC CallableStatements執行存儲過程

實驗目的：掌握jdbc callableStatements 的執行過程。

實驗內容：掌握jdbc callableStatements 的執行過程。

實驗過程：

CallableStatement的全部超級接口爲PreparedStatement、Statement、Wrapper。其中繼承自PreparedStatement接口。CallableStatement主要是調用數據庫中的存儲過程。在使用CallableStatement時能夠接收存儲過程的返回值。CallableStatement對象爲全部的DBMS提供了一種標準的形式去調用數據庫中已存在的存儲過程。對數據庫中存儲過程的調用是CallableStatement對象所含的內容。有兩種形式：1：形式帶結果參數；2：形式不帶結果參數。結果參數是一種輸出參數(存儲過程當中的輸出OUT參數)，是存儲過程的返回值。兩種形式都有帶有數量可變的輸入、輸出、輸入和輸出的參數。用問號作佔位符。

       形式帶結果參數語法格式：{ ? = call 存儲過程名[(?, ?, ?, ...)]};

       形式不帶結果參數語法格式：{ call 存儲過程名[(?, ?, ?, ...)]};PS方括號裏面的內容無關緊要。

       CallableStatement接口中經常使用的方法。

       1：getInt(int parameterIndex)、getInt(String parameterName)、還有getString、getBigDecimal、getString、getDate、getURL等等都相似和PreparedStatement與Statement中的用法相似。

       2：registerOutParameter(int parameterIndex, int sqlType):按順序位置parameterIndex將OUT參數註冊爲JDBC類型sqlType。

       3：wasNull():查詢最後一個讀取的OUT參數是否爲SQL Null。等等還有不少方法，感興趣的讀者能夠自行查閱JDK API文檔。

      講解了那麼多，不如一個例子來的痛快。下面經過一個例子讓讀者更清楚的看到CallableStatement的用法。

       首先在原先的t_employee表中添加表示幹了多少年的tyear字段。

alter table t_employee add tyear int;

在數據庫中編寫存儲過程統計指定id的userName的人，輸出一下他一共賺了多少錢。

      JDBC代碼：

 

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package com.panli.dbutil; /**  * 鏈接數據庫  */ import java.sql.CallableStatement; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement;    public class DbUtil {     //數據庫驅動名字     private static String jdbcName = "com.mysql.jdbc.Driver";     //數據庫協議地址     private static String dbUrl = "jdbc:mysql://localhost:3306/db_user";     //數據庫用戶名     private static String dbUser = "root";     //數據庫密碼     private static String dbPassword = "123456";                 /**      * 獲取鏈接      * @return      * @throws Exception      */     public static Connection getCon() throws Exception{         Class.forName(jdbcName);         Connection conn = DriverManager.getConnection(dbUrl, dbUser, dbPassword);         return conn;     }           /**      * 關閉鏈接      * @param stmt      * @param conn      * @throws Exception      */     public static void close(Statement stmt,Connection conn) throws Exception{         if(stmt!=null){             stmt.close();             if(conn!=null){                 conn.close();             }         }     }           /**      * 關閉鏈接      * @param cstmt      * @param conn      * @throws Exception      */     public static void close(CallableStatement cstmt, Connection conn) throws Exception{         if(cstmt!=null){             cstmt.close();             if(conn!=null){                 conn.close();             }         }     }                 /**      * 關閉鏈接      * @param pstmt      * @param conn      * @throws SQLException      */     public static void close(PreparedStatement pstmt, Connection conn) throws SQLException{         if(pstmt!=null){             pstmt.close();             if(conn!=null){                 conn.close();             }         }     }                 /**      * 重載關閉方法      * @param pstmt      * @param conn      * @throws Exception      */     public void close(ResultSet rs,PreparedStatement pstmt, Connection conn) throws Exception{         if(rs!=null){             rs.close();             if(pstmt!=null){                 pstmt.close();                 if(conn!=null){                     conn.close();                 }                               }         }               } }

 

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package com.panli.model;    import java.io.File;    /**  * model包下的cemployee類,對每一個字段進行建模  * @author Peter  *  */ public class CEmployee {     private int id;     private String userName;     private double salary;     private String job;     private int jobTypeId;     private File context;     private File pic;     private double counts;     /**      * 默認的構造方法      */     public CEmployee() {         super();         // TODO Auto-generated constructor stub     }           /**      * 帶一個參數的構造方法      * @param id      */     public CEmployee(int id) {         super();         this.id = id;     }           /**      * 兩個參數的構造方法      * @param counts      * @param userNames      */     public CEmployee(double counts, String userName) {         // TODO Auto-generated constructor stub         this.counts = counts;         this.userName = userName;     }        /**      * 重寫toString()方法      */     @Override     public String toString(){         return userName+"一共賺了"+counts+"錢";     }     public int getId() {         return id;     }     public void setId(int id) {         this.id = id;     }     public String getUserName() {         return userName;     }     public void setUserName(String userName) {         this.userName = userName;     }     public double getSalary() {         return salary;     }     public void setSalary(double salary) {         this.salary = salary;     }     public String getJob() {         return job;     }     public void setJob(String job) {         this.job = job;     }     public int getJobTypeId() {         return jobTypeId;     }     public void setJobTypeId(int jobTypeId) {         this.jobTypeId = jobTypeId;     }        public File getContext() {         return context;     }        public void setContext(File context) {         this.context = context;     }        public File getPic() {         return pic;     }        public void setPic(File pic) {         this.pic = pic;     }        public double getCounts() {         return counts;     }        public void setCounts(double counts) {         this.counts = counts;     }       }

 

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package com.panli.dao;    import java.sql.CallableStatement; import java.sql.Connection; import java.sql.Types; import java.util.ArrayList; import java.util.List;    import com.panli.dbutil.DbUtil; import com.panli.model.CEmployee;    public class CountsEmployeeDao {     private static DbUtil dbUtil = new DbUtil();     /**      * 調用存儲過程獲得指定ID用戶的一共賺了多少錢      * @param employee      * @return      * @throws Exception      */     public static List getCountsById(CEmployee cemployee)throws Exception{         List list = new ArrayList();         Connection conn = dbUtil.getCon();         String sql = "{call pro_getCountById(?, ?, ?)}";         CallableStatement cstmt = conn.prepareCall(sql);         cstmt.setInt(1, cemployee.getId());         cstmt.registerOutParameter(2, Types.DOUBLE);         cstmt.registerOutParameter(3, Types.VARCHAR);         cstmt.execute();         double counts = cstmt.getDouble("counts");         String userNames = cstmt.getString("userNames");         CEmployee emp = new CEmployee(counts, userNames);         list.add(emp);         dbUtil.close(cstmt, conn);         return list;     }     /**      * 作測試的主方法      * @param args      */     public static void main(String[] args)throws Exception {                   CEmployee cemployee = new CEmployee(1);         List list = getCountsById(cemployee);         for(CEmployee cemp: list){             System.out.println(cemp);         }     } }

建立的存儲過程爲：

 

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delimiter && create procedure pro_getCountById(in tid int, out counts double, out userNames varchar(20)) begin   select salary*tyear into counts from t_employee where id = tid;   select userName into userNames from t_employee where id = tid; end &&    測試： call pro_getCountById(1, @counts, @userNames); select @counts, @userNames;

 

1	alter table t_employee add tyear int ;

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