02-dbutils源碼之QueryRunner & 一個例子

時間 2019-11-09

標籤 dbutils 源碼 queryrunner 一個例子简体版

原文原文鏈接

在01中講了下AbstractQueryRunner的基本內容，對於JDBC比較熟悉的童鞋均可以很容易明白。接下來會分析下AbstractQueryRunner的子類QueryRunner。這個類是最經常使用的了。

      下面是類的繼承關係：

下面是類的outline

在這outline中，我圈出了要分析的源碼。重點在於分析當中的私有方法。由於私有方法是通用的。例如上圖中我圈中第一個和第二個公開方法query()內部就是調用第三個私有方法query()。

下面看一下詳細的說明

* Licensed to the Apache Software Foundation (ASF) under one or more

* contributor license agreements. See the NOTICE file distributed with

* this work for additional information regarding copyright ownership.

* The ASF licenses this file to You under the Apache License, Version 2.0

* (the "License"); you may not use this file except in compliance with

* the License. You may obtain a copy of the License at

* http://www.apache.org/licenses/LICENSE-2.0

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS IS" BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

package org. apache. commons. dbutils;

import java. sql. Connection;

import java. sql. PreparedStatement;

import java. sql. ResultSet;

import java. sql. SQLException;

import javax. sql. DataSource;

/**

* Executes SQL queries with pluggable strategies for handling

* <code>ResultSet</code>s. This class is thread safe.

* 執行SQL查詢語句，使用策略模式對結果進行處理。此類是線程安全的

* 這個類關聯到一個重要的接口：ResultSetHandler

* @see ResultSetHandler

public class QueryRunner extends AbstractQueryRunner {

/**

* Constructor for QueryRunner.

public QueryRunner() {

super();

}

/**

* Constructor for QueryRunner that controls the use of <code>ParameterMetaData</code>.

* @param pmdKnownBroken Some drivers don't support { @link java.sql.ParameterMetaData#getParameterType(int) };

* if <code>pmdKnownBroken</code> is set to true, we won't even try it; if false, we'll try it,

* and if it breaks, we'll remember not to use it again.

public QueryRunner( boolean pmdKnownBroken) {

super( pmdKnownBroken);

}

/**

* Constructor for QueryRunner that takes a <code>DataSource</code> to use.

* Methods that do not take a <code>Connection</code> parameter will retrieve connections from this

* <code>DataSource</code>.

* @param ds The <code>DataSource</code> to retrieve connections from.

public QueryRunner( DataSource ds) {

super( ds);

}

/**

* Constructor for QueryRunner that takes a <code>DataSource</code> and controls the use of <code>ParameterMetaData</code>.

* Methods that do not take a <code>Connection</code> parameter will retrieve connections from this

* <code>DataSource</code>.

* @param ds The <code>DataSource</code> to retrieve connections from.

* @param pmdKnownBroken Some drivers don't support { @link java.sql.ParameterMetaData#getParameterType(int) };

* if <code>pmdKnownBroken</code> is set to true, we won't even try it; if false, we'll try it,

* and if it breaks, we'll remember not to use it again.

public QueryRunner( DataSource ds, boolean pmdKnownBroken) {

super( ds, pmdKnownBroken);

}

/**

* Execute a batch of SQL INSERT, UPDATE, or DELETE queries.

* 批量處理INSERT、UPDATE、DELETE

* @param conn The Connection to use to run the query. The caller is

* responsible for closing this Connection.

* @param sql The SQL to execute.

* @param params An array of query replacement parameters. Each row in

* this array is one set of batch replacement values.

* @return The number of rows updated per statement.

* @throws SQLException if a database access error occurs

* @since DbUtils 1.1

public int[] batch( Connection conn, String sql, Object[][] params) throws SQLException {

return this. batch( conn, false, sql, params);

}

/**

* Execute a batch of SQL INSERT, UPDATE, or DELETE queries. The

* <code>Connection</code> is retrieved from the <code>DataSource</code>

* set in the constructor. This <code>Connection</code> must be in

* auto-commit mode or the update will not be saved.

* @param sql The SQL to execute.

* @param params An array of query replacement parameters. Each row in

* this array is one set of batch replacement values.

* @return The number of rows updated per statement.

* @throws SQLException if a database access error occurs

* @since DbUtils 1.1

public int[] batch( String sql, Object[][] params) throws SQLException {

Connection conn = this. prepareConnection();

return this. batch( conn, true, sql, params);

}

/**

* Calls update after checking the parameters to ensure nothing is null.

* @param conn The connection to use for the batch call.

* @param closeConn True if the connection should be closed, false otherwise.

* @param sql The SQL statement to execute.

* @param params An array of query replacement parameters. Each row in

* this array is one set of batch replacement values.

* @return The number of rows updated in the batch.

* @throws SQLException If there are database or parameter errors.

private int[] batch( Connection conn, boolean closeConn, String sql, Object[][] params) throws SQLException {

if ( conn == null) {

throw new SQLException( "Null connection");

}

if ( sql == null) {

if ( closeConn) {

close( conn);

}

throw new SQLException( "Null SQL statement");

}

if ( params == null) {

if ( closeConn) {

close( conn);

}

throw new SQLException( "Null parameters. If parameters aren't need, pass an empty array.");

}

PreparedStatement stmt = null;

int[] rows = null;

try {

stmt = this. prepareStatement( conn, sql);

for ( int i = 0; i < params. length; i ++) {

this. fillStatement( stmt, params[ i]);

stmt. addBatch();

}

rows = stmt. executeBatch();

} catch ( SQLException e) {

this. rethrow( e, sql, ( Object[]) params);

} finally {

close( stmt);

if ( closeConn) {

close( conn);

}

return rows;

}

/**

* Execute an SQL SELECT query with a single replacement parameter. The

* caller is responsible for closing the connection.

* @param <T> The type of object that the handler returns

* @param conn The connection to execute the query in.

* @param sql The query to execute.

* @param param The replacement parameter.

* @param rsh The handler that converts the results into an object.

* @return The object returned by the handler.

* @throws SQLException if a database access error occurs

* @deprecated Use { @link #query(Connection, String, ResultSetHandler, Object...)}

@ Deprecated

public < T > T query( Connection conn, String sql, Object param, ResultSetHandler < T > rsh) throws SQLException {

return this. < T > query( conn, false, sql, rsh, new Object[]{ param});

}

/**

* Execute an SQL SELECT query with replacement parameters. The

* caller is responsible for closing the connection.

* @param <T> The type of object that the handler returns

* @param conn The connection to execute the query in.

* @param sql The query to execute.

* @param params The replacement parameters.

* @param rsh The handler that converts the results into an object.

* @return The object returned by the handler.

* @throws SQLException if a database access error occurs

* @deprecated Use { @link #query(Connection,String,ResultSetHandler,Object...)} instead

@ Deprecated

public < T > T query( Connection conn, String sql, Object[] params, ResultSetHandler < T > rsh) throws SQLException {

return this. < T > query( conn, false, sql, rsh, params);

}

/**

* Execute an SQL SELECT query with replacement parameters. The

* caller is responsible for closing the connection.

* @param <T> The type of object that the handler returns

* @param conn The connection to execute the query in.

* @param sql The query to execute.

* @param rsh The handler that converts the results into an object.

* @param params The replacement parameters.

* @return The object returned by the handler.

* @throws SQLException if a database access error occurs

public < T > T query( Connection conn, String sql, ResultSetHandler < T > rsh, Object... params) throws SQLException {

return this. < T > query( conn, false, sql, rsh, params);

}

/**

* Execute an SQL SELECT query without any replacement parameters. The

* caller is responsible for closing the connection.

* @param <T> The type of object that the handler returns

* @param conn The connection to execute the query in.

* @param sql The query to execute.

* @param rsh The handler that converts the results into an object.

* @return The object returned by the handler.

* @throws SQLException if a database access error occurs

public < T > T query( Connection conn, String sql, ResultSetHandler < T > rsh) throws SQLException {

return this. < T > query( conn, false, sql, rsh, ( Object[]) null);

}

/**

* Executes the given SELECT SQL with a single replacement parameter.

* The <code>Connection</code> is retrieved from the

* <code>DataSource</code> set in the constructor.

* @param <T> The type of object that the handler returns

* @param sql The SQL statement to execute.

* @param param The replacement parameter.

* @param rsh The handler used to create the result object from

* the <code>ResultSet</code>.

* @return An object generated by the handler.

* @throws SQLException if a database access error occurs

* @deprecated Use { @link #query(String, ResultSetHandler, Object...)}

@ Deprecated

public < T > T query( String sql, Object param, ResultSetHandler < T > rsh) throws SQLException {

Connection conn = this. prepareConnection();

return this. < T > query( conn, true, sql, rsh, new Object[]{ param});

}

/**

* Executes the given SELECT SQL query and returns a result object.

* The <code>Connection</code> is retrieved from the

* <code>DataSource</code> set in the constructor.

* 這個方法使用的是數組參數，後來改爲使用了可變參數

* @param <T> The type of object that the handler returns

* @param sql The SQL statement to execute.

* @param params Initialize the PreparedStatement's IN parameters with

* this array.

* @param rsh The handler used to create the result object from

* the <code>ResultSet</code>.

* @return An object generated by the handler.

* @throws SQLException if a database access error occurs

* @deprecated Use { @link #query(String, ResultSetHandler, Object...)}

@ Deprecated

public < T > T query( String sql, Object[] params, ResultSetHandler < T > rsh) throws SQLException {

Connection conn = this. prepareConnection();

return this. < T > query( conn, true, sql, rsh, params);

}

/**

* Executes the given SELECT SQL query and returns a result object.

* 執行給定的查詢語句，返回一個結果對象

* The <code>Connection</code> is retrieved from the

* <code>DataSource</code> set in the constructor.

* 在方法內部：從數據源中獲得鏈接

* @param <T> The type of object that the handler returns

* @param sql The SQL statement to execute.

* @param rsh The handler used to create the result object from

* the <code>ResultSet</code>.

* 此handler是用來對ResultSet進行處理的，使用了策略模式

* @param params Initialize the PreparedStatement's IN parameters with

* this array.

* @return An object generated by the handler.

* @throws SQLException if a database access error occurs

public < T > T query( String sql, ResultSetHandler < T > rsh, Object... params) throws SQLException {

//獲得數據庫連接。繼承過來的方法。

Connection conn = this. prepareConnection();

return this. < T > query( conn, true, sql, rsh, params);

}

/**

* Executes the given SELECT SQL without any replacement parameters.

* 執行查詢語句，這個查詢語句沒有使用到參數，例如：select * from t_user

* The <code>Connection</code> is retrieved from the

* <code>DataSource</code> set in the constructor.

* @param <T> The type of object that the handler returns

* @param sql The SQL statement to execute.

* @param rsh The handler used to create the result object from

* the <code>ResultSet</code>.

* @return An object generated by the handler.

* @throws SQLException if a database access error occurs

public < T > T query( String sql, ResultSetHandler < T > rsh) throws SQLException {

//獲得數據庫連接。繼承過來的方法。

Connection conn = this. prepareConnection();

return this. < T > query( conn, true, sql, rsh, ( Object[]) null);

}

/**

* Calls query after checking the parameters to ensure nothing is null.

* @param conn The connection to use for the query call.

* @param closeConn True if the connection should be closed, false otherwise.

* @param sql The SQL statement to execute.

* @param params An array of query replacement parameters. Each row in

* this array is one set of batch replacement values.

* @return The results of the query.

* @throws SQLException If there are database or parameter errors.

private < T > T query( Connection conn, boolean closeConn, String sql, ResultSetHandler < T > rsh, Object... params)

throws SQLException {

//數據庫連接爲null，那麼報錯

if ( conn == null) {

throw new SQLException( "Null connection");

}

//SQL語句爲null，報錯。沒語句，執行什麼呢？

if ( sql == null) {

if ( closeConn) { //SQL語句都爲空，要數據庫連接幹什麼

close( conn);

}

throw new SQLException( "Null SQL statement");

}

//結果集爲null，報錯。

if ( rsh == null) {

if ( closeConn) {

close( conn);

}

throw new SQLException( "Null ResultSetHandler");

}

//定義一個PreparedStatement類型變量

PreparedStatement stmt = null;

//定義一個ResultSet類型變量

ResultSet rs = null;

T result = null; //泛型。用戶最終要的結果

try {

//準備PreparedStatement對象，此方法是從父類繼承過來的

stmt = this. prepareStatement( conn, sql);

//填充?佔位符，此方法是從父類繼承過來的

this. fillStatement( stmt, params);

//執行SQL語句。包裝結果集，此方法是從父類繼承過來的，其實wrap只是把傳進去的RS又return了

rs = this. wrap( stmt. executeQuery());

/**

* 對結果集進行處理。策略模式。對於結果進行如何處理，交由用戶處理。dbutils已經實現了常用的

* ResultSetHandler。用戶可以實現自己的ResultSetHandler，只要實現接口

* ResultSetHandler即可

result = rsh. handle( rs);

} catch ( SQLException e) {

this. rethrow( e, sql, params);

} finally { //釋放資源

try {

close( rs);

} finally {

close( stmt);

if ( closeConn) {

close( conn);

}

//返回用戶要的結果。此結果就是ResultSetHandler中的handle方法返回的結果

return result;

}

/**

* Execute an SQL INSERT, UPDATE, or DELETE query without replacement

* parameters.

* 這裏執行的是不帶參數的SQL語句

* @param conn The connection to use to run the query.

* @param sql The SQL to execute.

* @return The number of rows updated.

* @throws SQLException if a database access error occurs

public int update( Connection conn, String sql) throws SQLException {

return this. update( conn, false, sql, ( Object[]) null);

}

/**

* Execute an SQL INSERT, UPDATE, or DELETE query with a single replacement

* parameter.

* @param conn The connection to use to run the query.

* @param sql The SQL to execute.

* @param param The replacement parameter.

* @return The number of rows updated.

* @throws SQLException if a database access error occurs

public int update( Connection conn, String sql, Object param) throws SQLException {

return this. update( conn, false, sql, new Object[]{ param});

}

/**

* Execute an SQL INSERT, UPDATE, or DELETE query.

* @param conn The connection to use to run the query.

* @param sql The SQL to execute.

* @param params The query replacement parameters.

* @return The number of rows updated.

* @throws SQLException if a database access error occurs

public int update( Connection conn, String sql, Object... params) throws SQLException {

return update( conn, false, sql, params);

}

/**

* Executes the given INSERT, UPDATE, or DELETE SQL statement without

* any replacement parameters. The <code>Connection</code> is retrieved

* from the <code>DataSource</code> set in the constructor. This

* <code>Connection</code> must be in auto-commit mode or the update will

* not be saved.

* 執行給定的INSERT,UPDATE,或DELETE語句，語句中沒有可替代的參數。Connection從數據源中獲得。

* 這個連接必須爲自動提交模式。，否則更新操做不會被保存。

* @param sql The SQL statement to execute.

* @throws SQLException if a database access error occurs

* @return The number of rows updated.

public int update( String sql) throws SQLException {

Connection conn = this. prepareConnection();

//執行，因爲沒使用到參數，所以給個null

return this. update( conn, true, sql, ( Object[]) null);

}

/**

* Executes the given INSERT, UPDATE, or DELETE SQL statement with

* a single replacement parameter. The <code>Connection</code> is

* retrieved from the <code>DataSource</code> set in the constructor.

* This <code>Connection</code> must be in auto-commit mode or the

* update will not be saved.

* 執行給定的INSERT,UPDATE,或DELETE語句，語句中有且僅有一個可替代的參數。Connection從數據源中獲得。

* 這個連接必須爲自動提交模式。，否則更新操做不會被保存。

* @param sql The SQL statement to execute.

* @param param The replacement parameter.

* @throws SQLException if a database access error occurs

* @return The number of rows updated.

public int update( String sql, Object param) throws SQLException {

Connection conn = this. prepareConnection();

return this. update( conn, true, sql, new Object[]{ param});

}

/**

* Executes the given INSERT, UPDATE, or DELETE SQL statement. The

* <code>Connection</code> is retrieved from the <code>DataSource</code>

* set in the constructor. This <code>Connection</code> must be in

* auto-commit mode or the update will not be saved.

* 執行給定的INSERT,UPDATE,或DELETE語句，語句中有多個可替代的參數。Connection從數據源中獲得。

* 這個連接必須爲自動提交模式。，否則更新操做不會被保存。

* @param sql The SQL statement to execute.

* @param params Initializes the PreparedStatement's IN (i.e. '?')

* parameters.

* @throws SQLException if a database access error occurs

* @return The number of rows updated.

public int update( String sql, Object... params) throws SQLException {

Connection conn = this. prepareConnection();

return this. update( conn, true, sql, params);

}

/**

* Calls update after checking the parameters to ensure nothing is null.

* 在調用update操做前，檢查一下參數，確保沒有爲null的

* @param conn The connection to use for the update call.

* @param closeConn True if the connection should be closed, false otherwise.

* @param sql The SQL statement to execute.

* @param params An array of update replacement parameters. Each row in

* this array is one set of update replacement values.

* @return The number of rows updated.

* @throws SQLException If there are database or parameter errors.

private int update( Connection conn, boolean closeConn, String sql, Object... params) throws SQLException {

//鏈接都沒，怎麼操做，報錯得了

if ( conn == null) {

throw new SQLException( "Null connection");

}

//SQL都沒，怎麼操做，報錯得了。closeConn爲true，就關閉鏈接

if ( sql == null) {

if ( closeConn) {

//這裏的close是從父類繼承過來的

close( conn);

}

throw new SQLException( "Null SQL statement");

}

//定義一個PreparedStatement類型變量

PreparedStatement stmt = null;

//這裏記錄的是受影響的函數。如update了幾行，insert了幾行，delete了幾行

int rows = 0;

try {

//獲得prepareStatement變量，此方法是從父類繼承過來的

stmt = this. prepareStatement( conn, sql);

//爲prepareStatement中的參數賦值

this. fillStatement( stmt, params);

//執行SQL，返回受影響行數

rows = stmt. executeUpdate();

} catch ( SQLException e) {

this. rethrow( e, sql, params);

} finally { //釋放資源

close( stmt);

if ( closeConn) {

close( conn);

}

//返回結果

return rows;

}

以私有的query()進行一下說明：
在JDBC中，咱們經過Connection拿到PreparedStatement，就要爲PreparedStatement進行設置參數。而後execute，返回了ResultSet，而後就要對ResultSet進行處理。
在DBUtils中，只不過是對各個步驟進行了封裝。
得到PreparedStatement，就是this.prepareStatement(conn, sql);
爲PreparedStatement進行設置參數：this.fillStatement(stmt, params);
對ResultSet進行處理：rsh.handle(rs);，rsh是ResultSetHandler接口類型的。rs就是ResultSet。

下面會經過一個例子，讓你們瞭解dbutils的基本使用

-------------------------------------------------------------------------------------------------------------------------------------------------------------------
一、數據庫，數據庫名是testdb

MySQL Data Transfer

Source Host: localhost

Source Database: testdb

Target Host: localhost

Target Database: testdb

Date: 2013/9/12 10:19:21

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------

-- Table structure for t_user

-- ----------------------------

DROP TABLE IF EXISTS `t_user`;

CREATE TABLE `t_user` (

`id` int(11) NOT NULL AUTO_INCREMENT,

`name` varchar(40) DEFAULT NULL,

`birthday` date DEFAULT NULL,

PRIMARY KEY (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

-- ----------------------------

-- Records

-- ----------------------------

INSERT INTO `t_user` VALUES ('1', '黃錦成', '2013-09-11');

INSERT INTO `t_user` VALUES ('2', 'zxx', '2012-09-11');

二、jar包

三、數據源幫助類

/**

* 數據源幫助類。使用的是C3P0。

* @author Administrator

public class DataSourceUtil {

private static ComboPooledDataSource cpds = null;

static{

cpds = new ComboPooledDataSource();

try {

cpds. setDriverClass( "com.mysql.jdbc.Driver" );

cpds. setJdbcUrl( "jdbc:mysql:///testdb" );

cpds. setUser( "root");

cpds. setPassword( "123");

} catch ( PropertyVetoException e) {

throw new RuntimeException( e);

}

public static DataSource getDataSource(){

if( cpds == null){

throw new RuntimeException( "數據源爲null");

}

return cpds;

}

四、javabean

import java. util. Date;

public class User {

private Integer id;

private String name;

private Date birthday;

public Integer getId() {

return id;

}

public void setId( Integer id) {

this. id = id;

}

public String getName() {

return name;

}

public void setName( String name) {

this. name = name;

}

public Date getBirthday() {

return birthday;

}

public void setBirthday( Date birthday) {

this. birthday = birthday;

}

@ Override

public String toString() {

return "User [id=" + id + ", name=" + name + ", birthday=" + birthday

+ "]";

}

五、進行測試

這裏進行的是update測試

package com. hjc. dbutils. test;

import java. util. Date;

import org. apache. commons. dbutils. QueryRunner;

import org. junit. Before;

import org. junit. Test;

import com. hjc. dbutils. utils. DataSourceUtil;

public class UpdateTest {

* 創建QueryRunner對象

QueryRunner queryRunner = null;

@ Before

public void setUp(){

queryRunner = new QueryRunner( DataSourceUtil. getDataSource());

}

* 調用QueryRunner的update方法

* update、insert、delete操做對於數據庫來說，都是更新操做

* 所以QueryRunner中的update方法中的sql語句可以是update、insert、delete語句

@ Test

public void testUpdate() throws Exception{

String sql = "insert into t_user(name,birthday) values(?,?)";

Object[] params = new Object[]{ "hjc", new Date()};

queryRunner. update( sql, params);

}

這裏進行的是query測試

package com. hjc. dbutils. test;

import java. util. Date;

import org. apache. commons. dbutils. QueryRunner;

import org. apache. commons. dbutils. ResultSetHandler;

import org. apache. commons. dbutils. handlers. BeanHandler;

import org. junit. Before;

import org. junit. Test;

import com. hjc. dbutils. domain. User;

import com. hjc. dbutils. utils. DataSourceUtil;

public class BeanHandlerTest {

QueryRunner queryRunner = null;

@ Before

public void setUp(){

queryRunner = new QueryRunner( DataSourceUtil. getDataSource());

}

@ Test

public void testBeanHandler() throws Exception{

String sql = "select * from t_user where id=?";

Object[] params = new Object[]{ 1};

ResultSetHandler < User > rsh = new BeanHandler < User >( User. class);

User userResult = queryRunner. query( sql, rsh, params);

System. out. println( userResult);

}

/**

* 當有多行時，使用BeanHandler，只會處理第一行記錄

* @throws Exception

@ Test

public void testBeanHandler2() throws Exception{

String sql = "select * from t_user";

ResultSetHandler < User > rsh = new BeanHandler < User >( User. class);

User userResult = queryRunner. query( sql, rsh);

System. out. println( userResult);

}

BeanHandler是用於對一行記錄進行處理的，它將一行記錄轉換成一個javabean對象。轉換是如何實現的呢？它使用了反射技術。
javabean的屬性和數據庫表字段之間又是怎樣映射的呢？咱們在設計時，會把javabean屬性和表字段設置爲同樣的。例如javabean中是id、name、birthday，那麼在數據庫表中的字段就是id、name、birthday。

上面使用的 BeanHandler 是 ResultSet 的一個實現類。

能夠看到有個BeanListHandler，那麼這個與BeanHandler什麼關係呢？BeanHandler是將一行記錄變成一個javabean對象，那麼BeanListHandler就是將多行記錄變成多個javabean對象，而後將這些javabean對象放入到一個List集合中。
BeanHandler是用來處理ResultSet中的第一行記錄的，除了第一行記錄，其餘的都不處理。想處理多行的，那麼就用BeanListHandler吧!

下面簡單說下其餘Handler的用法：
ArrayHandler：將一行記錄變成一個數組，ArrayListHandler就是一個數組的List集合
MapHandler：將一行記錄變成一個Map對象，列名爲key，列值爲value，MapListHandler就是一個Map對象的List集合

上面總共講了6個Handler，都是比較經常使用的，以後的源碼分析會重點進行講解。

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