mybatis的typeHandler

typehandler作用：

　　1.传参时将javatype类型转换成jdbctype

　　2.结果集中resultset中取值时，jdbctype转换为javatype;

系统自定义的typehandler:

　　mybatis系统内部定义了一系列的typehandler；基本涵盖了我们正常使用的类型转换；如下

选取一个系统自定义的typehandler看看；

在包org.apache.ibatis.type下有一个stringtypehandler.java

源码如下：

public class stringtypehandler extends basetypehandler<string> {

  @override
  public void setnonnullparameter(preparedstatement ps, int i, string parameter, jdbctype jdbctype)
      throws sqlexception {
    ps.setstring(i, parameter);
  }

  @override
  public string getnullableresult(resultset rs, string columnname)
      throws sqlexception {
    return rs.getstring(columnname);
  }

  @override
  public string getnullableresult(resultset rs, int columnindex)
      throws sqlexception {
    return rs.getstring(columnindex);
  }

  @override
  public string getnullableresult(callablestatement cs, int columnindex)
      throws sqlexception {
    return cs.getstring(columnindex);
  }
}

view code

stringtypehandler继承了basetypehandler;而basetypehandler实现了接口typehandler,

basetypehandler中代码

/**
 *    copyright 2009-2015 the original author or authors.
 *
 *    licensed 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.ibatis.type;

import java.sql.callablestatement;
import java.sql.preparedstatement;
import java.sql.resultset;
import java.sql.sqlexception;

import org.apache.ibatis.executor.result.resultmapexception;
import org.apache.ibatis.session.configuration;

/**
 * @author clinton begin
 * @author simone tripodi
 */
public abstract class basetypehandler<t> extends typereference<t> implements typehandler<t> {

  protected configuration configuration;

  public void setconfiguration(configuration c) {
    this.configuration = c;
  }

  @override
  public void setparameter(preparedstatement ps, int i, t parameter, jdbctype jdbctype) throws sqlexception {
    if (parameter == null) {
      if (jdbctype == null) {
        throw new typeexception("jdbc requires that the jdbctype must be specified for all nullable parameters.");
      }
      try {
        ps.setnull(i, jdbctype.type_code);
      } catch (sqlexception e) {
        throw new typeexception("error setting null for parameter #" + i + " with jdbctype " + jdbctype + " . " +
                "try setting a different jdbctype for this parameter or a different jdbctypefornull configuration property. " +
                "cause: " + e, e);
      }
    } else {
      try {
        setnonnullparameter(ps, i, parameter, jdbctype);
      } catch (exception e) {
        throw new typeexception("error setting non null for parameter #" + i + " with jdbctype " + jdbctype + " . " +
                "try setting a different jdbctype for this parameter or a different configuration property. " +
                "cause: " + e, e);
      }
    }
  }

  @override
  public t getresult(resultset rs, string columnname) throws sqlexception {
    t result;
    try {
      result = getnullableresult(rs, columnname);
    } catch (exception e) {
      throw new resultmapexception("error attempting to get column '" + columnname + "' from result set.  cause: " + e, e);
    }
    if (rs.wasnull()) {
      return null;
    } else {
      return result;
    }
  }

  @override
  public t getresult(resultset rs, int columnindex) throws sqlexception {
    t result;
    try {
      result = getnullableresult(rs, columnindex);
    } catch (exception e) {
      throw new resultmapexception("error attempting to get column #" + columnindex+ " from result set.  cause: " + e, e);
    }
    if (rs.wasnull()) {
      return null;
    } else {
      return result;
    }
  }

  @override
  public t getresult(callablestatement cs, int columnindex) throws sqlexception {
    t result;
    try {
      result = getnullableresult(cs, columnindex);
    } catch (exception e) {
      throw new resultmapexception("error attempting to get column #" + columnindex+ " from callable statement.  cause: " + e, e);
    }
    if (cs.wasnull()) {
      return null;
    } else {
      return result;
    }
  }

  public abstract void setnonnullparameter(preparedstatement ps, int i, t parameter, jdbctype jdbctype) throws sqlexception;

  public abstract t getnullableresult(resultset rs, string columnname) throws sqlexception;

  public abstract t getnullableresult(resultset rs, int columnindex) throws sqlexception;

  public abstract t getnullableresult(callablestatement cs, int columnindex) throws sqlexception;

}

view code

 

getresult分别用columnname和columnindex从resultset中获取数据，callablestatement表示从存储过程中获取结果及数据的方法；

下面我们创建自定义typehandler

rolemapper.java

package com.learn.charter2.mapper;

import java.util.list;

import com.learn.charter2.po.role;

public interface rolemapper {
    role getrole(long id) throws exception;
    int deleterole(long id) throws exception;
    int insertrole(role role) throws exception;
    list<role> findrole(role role) throws exception;
}

view code

role.java

package com.learn.charter2.po;

public class role {
    private long id;
    private string rolename;
    private string note;
    private integer pk;
    
    public long getid() {
        return id;
    }
    public void setid(long id) {
        this.id = id;
    }
    public string getrolename() {
        return rolename;
    }
    public void setrolename(string rolename) {
        this.rolename = rolename;
    }
    public string getnote() {
        return note;
    }
    public void setnote(string note) {
        this.note = note;
    }
    public integer getpk() {
        return pk;
    }
    public void setpk(integer pk) {
        this.pk = pk;
    }
    

    

}

view code

sqlsessionfactoryutil.java

package com.learn.charter2.util;

import java.io.inputstream;
import java.util.logging.level;
import java.util.logging.logger;

import org.apache.ibatis.io.resources;
import org.apache.ibatis.session.sqlsession;
import org.apache.ibatis.session.sqlsessionfactory;
import org.apache.ibatis.session.sqlsessionfactorybuilder;

public class sqlsessionfactoryutil {
    private static sqlsessionfactory sqlsessionfactory=null;
    private static final class class_lock=sqlsessionfactoryutil.class;
    private sqlsessionfactoryutil() {
    }
    public static sqlsessionfactory initsqlsessionfactory(){
        string resource="mybatis-config.xml";
        inputstream inputstream=null;
        try {
            inputstream=resources.getresourceasstream(resource);
        } catch (exception e) {
            logger.getlogger(sqlsessionfactoryutil.class.getname()).log(level.severe,null,e);
        }
        synchronized (class_lock) {
            if(sqlsessionfactory==null){
                sqlsessionfactory=new sqlsessionfactorybuilder().build(inputstream);
            }
        }
        return sqlsessionfactory;
    }
    public static sqlsession opensqlsession(){
        if(sqlsessionfactory==null){
            initsqlsessionfactory();
        }
        return sqlsessionfactory.opensession();
    }
}

view code

log4j.properties

log4j.rootlogger=debug,stdout
log4j.logger.org.mybatis=debug
log4j.appender.stdout=org.apache.log4j.consoleappender
log4j.appender.stdout.layout=org.apache.log4j.patternlayout
log4j.appender.stdout.layout.conversionpattern=%5p %d %c:%m%n

 

mybatis-config.xml

 1 <?xml version="1.0" encoding="utf-8" ?> <!doctype configuration  public "-//mybatis.org//dtd config 3.0//en"  "http://mybatis.org/dtd/mybatis-3-config.dtd">
 2 <configuration>
 3     <typehandlers>
 4         <typehandler handler="com.learn.charter2.util.mystringtypehandler" javatype="string" jdbctype="varchar"/>
 5         <typehandler handler="com.learn.charter2.util.myintergertypehandler" javatype="int" jdbctype="varchar"/>
 6     </typehandlers>
 7     <environments default="development">
 8         <environment id="development">
 9             <transactionmanager type="jdbc">
10                 <property name="autocommit" value="false" />
11             </transactionmanager>
12             <datasource type="pooled">
13                 <property name="driver" value="com.mysql.jdbc.driver" />
14                 <property name="url" value="jdbc:mysql://localhost:3306/mybatis" />
15                 <property name="username" value="root" />
16                 <property name="password" value="gys" />
17             </datasource>
18         </environment>
19     </environments>
20     <mappers>
21         <mapper resource="com/learn/charter2/mapper/rolemapper.xml" />
22     </mappers>
23 </configuration>

 

rolemapper.xml

 1 <?xml version="1.0" encoding="utf-8" ?> <!doctype mapper  public "-//mybatis.org//dtd mapper 3.0//en"  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 2 <mapper namespace="com.learn.charter2.mapper.rolemapper">
 3     
 4     <resultmap type="com.learn.charter2.po.role" id="rolemap">
 5         <id column="id" property="id" javatype="long" jdbctype="bigint"/>
 6         <result column="role_name" property="rolename" javatype="string" jdbctype="varchar"/>
 7         <result column="note" property="note" typehandler="com.learn.charter2.util.mystringtypehandler"/>
 8         <result column="pk" property="pk" typehandler="com.learn.charter2.util.myintergertypehandler"/>
 9     </resultmap>
10 
11 
12     <select id="getrole" parametertype="long" resultmap="rolemap"> 
13     select id,role_name as rolename,note from t_role where id=#{id}
14     </select>
15     
16     <select id="findrole" parametertype="com.learn.charter2.po.role" resultmap="rolemap"> 
17     select id,role_name as rolename,note,pk from t_role 
18     <where>
19         <if test="rolename !=null">
20              role_name like concat('%',#{rolename,javatype=string,jdbctype=varchar,typehandler=com.learn.charter2.util.mystringtypehandler},'%')
21         </if>
22         <if test="pk !=null">
23         and pk =#{pk,javatype=int,jdbctype=varchar,typehandler=com.learn.charter2.util.myintergertypehandler}
24          </if> 
25     </where>    
26 
27 
28     </select>
29     
30     <insert id="insertrole" parametertype="com.learn.charter2.po.role">
31         insert into t_role
32         (role_name,note)
33         values
34         (#{rolename},#{note})
35     </insert>
36     <delete id="deleterole" parametertype="long">
37         delete from t_role where id=#{id}
38     </delete>
39 </mapper>

myintergertypehandler.java

 1 package com.learn.charter2.util;
 2 
 3 
 4 import java.sql.callablestatement;
 5 import java.sql.preparedstatement;
 6 import java.sql.resultset;
 7 import java.sql.sqlexception;
 8 
 9 import org.apache.ibatis.type.jdbctype;
10 import org.apache.ibatis.type.mappedjdbctypes;
11 import org.apache.ibatis.type.mappedtypes;
12 import org.apache.ibatis.type.typehandler;
13 import org.apache.log4j.logger;
14 
15 import sun.security.action.getintegeraction;
16 
17 
18 /**
19  * @mappedtypes({integer.class})
20    @mappedjdbctypes(jdbctype.varchar)
21  *
22  */
23 public class myintergertypehandler implements typehandler<integer> {
24     
25     private logger log=logger.getlogger(myintergertypehandler.class);
26 
27     private int getint(string v){
28         if("a".equals(v)){
29             return 10;
30         }else if("b".equals(v)){
31             return 20;
32         }else if("c".equals(v)){
33              return 30;
34         }else{
35             return 60;
36         }
37     }
38     @override
39     public integer getresult(callablestatement cs, int index)
40             throws sqlexception {
41         log.info("使用我的integertypehandler,callblestatment下表获取字符串");
42         return getint(cs.getstring(index));
43     }
44 
45     @override
46     public integer getresult(resultset rs, int index) throws sqlexception {
47         log.info("使用我的integertypehandler,resultset下标获取字符串");
48         return getint(rs.getstring(index));
49     }
50 
51     @override
52     public integer getresult(resultset rs, string colname) throws sqlexception {
53         log.info("使用我的integertypehandler,resultset 列名获取字符串");
54         return getint(rs.getstring(colname));
55     }
56 
57     @override
58     public void setparameter(preparedstatement ps, int index, integer value,jdbctype jt) throws sqlexception {
59         log.info("使用我的integertypehandler==index:"+index+";value:"+value);
60         string v="";
61         if(value==1){
62             v="a";
63         }else if(value==2){
64             v="b";
65         }else if(value==3){
66             v="c";
67         }else {
68             v="guoyansi";
69         }
70         ps.setstring(index, v);
71     }
72 }

mystringtypehandler.java

 1 package com.learn.charter2.util;
 2 
 3 
 4 import java.sql.callablestatement;
 5 import java.sql.preparedstatement;
 6 import java.sql.resultset;
 7 import java.sql.sqlexception;
 8 
 9 import org.apache.ibatis.type.jdbctype;
10 import org.apache.ibatis.type.mappedjdbctypes;
11 import org.apache.ibatis.type.mappedtypes;
12 import org.apache.ibatis.type.typehandler;
13 import org.apache.log4j.logger;
14 
15 
16 @mappedtypes({string.class})
17 @mappedjdbctypes(jdbctype.integer)
18 public class mystringtypehandler implements typehandler<string> {
19     private logger log=logger.getlogger(mystringtypehandler.class);
20     
21     @override
22     public string getresult(callablestatement cs, int index)
23             throws sqlexception {
24         log.info("使用我的stringtypehandler,callblestatment下表获取字符串");
25         return cs.getstring(index);
26     }
27 
28     @override
29     public string getresult(resultset rs, int index) throws sqlexception {
30         log.info("使用我的stringtypehandler,resultset下标获取字符串");
31         return rs.getstring(index);
32     }
33 
34     @override
35     public string getresult(resultset rs, string colname) throws sqlexception {
36         log.info("使用我的stringtypehandler,resultset 列名获取字符串");
37         return rs.getstring(colname);
38     }
39 
40     @override
41     public void setparameter(preparedstatement ps, int index, string value,
42             jdbctype jt) throws sqlexception {
43         value=value+"m";
44         log.info("使用我的stringtypehandler==index:"+index+";value:"+value);
45         ps.setstring(index, value);
46     }
47     
48     
49 }

charter2main.java

 1 package com.learn.charter2.main;
 2 
 3 import java.util.list;
 4 
 5 import org.apache.ibatis.session.sqlsession;
 6 
 7 import com.learn.charter2.mapper.rolemapper;
 8 import com.learn.charter2.po.role;
 9 import com.learn.charter2.util.sqlsessionfactoryutil;
10 
11 public class charter2main {
12     public static void main(string[] args) {
13         sqlsession sqlsession = null;
14         try {
15             sqlsession = sqlsessionfactoryutil.opensqlsession();
16             rolemapper rolemapper = sqlsession.getmapper(rolemapper.class);
17             role role = new role();
18             role.setpk(10);
19             list<role> list=rolemapper.findrole(role);
20             for(role r:list){
21                 system.out.println("id:"+r.getid()+";rolename:"+r.getrolename()+";note:"+r.getnote()+";pk:"+r.getpk());
22             }
23         } catch (exception e) {
24             system.err.println(e.getmessage());
25             sqlsession.rollback();
26         }finally{
27             if(sqlsession!=null){
28                 sqlsession.close();
29             }
30         }
31     }
32 
33 }

自定义typehandler的三个步骤：

1.定义typehandler(myintergertypehandler.java     mystringtypehandler.java)

2.配置typehandler(mybatis-config.xml中3-6行)

3.指定入参中哪个字段使用typehandler(mapper.xml中19-24行)

4.指定出参中哪个字段使用typehandler(mapper.xml中7-8行)

以myintergertypehandler为例，运行一下charter2main.java

charter2main 中传入的pk参数是10，被typehandler默默的转换成了guoyansi;
因为guoyansi在数据库中找到了值，在被返回到java中，guoyansi又被typehandler转化成了60；
这个例子展示的就是integer和string之间的转换。