MyBatis SQL mapping File Select tag and application to Resultmap tag

1. Customize the packaging rules for a javabean:

650) this.width=650; "src=" Https://s2.51cto.com/wyfs02/M01/97/9F/wKioL1kwrCvxpj4pAAArdWlULiQ058.png "title=" 91. PNG "alt=" Wkiol1kwrcvxpj4paaardwluliq058.png "/>

650) this.width=650; "src=" Https://s2.51cto.com/wyfs02/M02/97/9F/wKioL1kwrAOA8hzvAABwPHDeTls926.png "style=" float : none; "title=" 92.png "alt=" Wkiol1kwraoa8hzvaabwphdetls926.png "/>

Note: You can see that the value of the defined Resultmap is referenced in the select tag. The type in the Resultmap tag is JavaBean and the ID is a unique identifier. The ID sub-tag defines the primary key (this defines the bottom layer as an optimization.) The Column property is the field name and the property attribute is the field value.

650) this.width=650; "src=" Https://s2.51cto.com/wyfs02/M00/97/9E/wKiom1kwrATQ5dDRAAAwwVNL06Q580.png "style=" float : none; "title=" 93.png "alt=" Wkiom1kwratq5ddraaawwvnl06q580.png "/>

650) this.width=650; "src=" Https://s2.51cto.com/wyfs02/M02/97/9F/wKioL1kwrASD9pczAABBzqADOd0639.png "style=" float : none; "title=" 94.png "alt=" Wkiol1kwrasd9pczaabbzqadod0639.png "/>

Note: You can see that there is no problem with the test results and that the code is not error.

2. Customize the cascading properties of a JavaBean encapsulation:

A, preparation: MySQL database, on the basis of the previous Tbl_employees table (previous blog example), create a tbl_depts table, and add a d_id field in the Tbl_employees table, and establish a foreign key associated with the Tbl_depts table 。 (and test the SQL statement in the SQL script compiler of the SQLyog software) and add the Department attribute and the corresponding Set/get method to the Employee class.

650) this.width=650; "src=" Https://s2.51cto.com/wyfs02/M02/97/C1/wKiom1kyZyLxPjbhAAFhBZBWa5o609.png "title=" 95. PNG "alt=" Wkiom1kyzylxpjbhaafhbzbwa5o609.png "/>

650) this.width=650; "src=" Https://s3.51cto.com/wyfs02/M02/97/C1/wKiom1kyZyPwZ4iaAAAg3RDzVwg727.png "title=" 96. PNG "alt=" Wkiom1kyzypwz4iaaaag3rdzvwg727.png "/>

650) this.width=650; "src=" Https://s3.51cto.com/wyfs02/M02/97/C2/wKioL1kyZyOjFGexAAAsrhgMSG8134.png "title=" 97. PNG "alt=" Wkiol1kyzyojfgexaaasrhgmsg8134.png "/>

650) this.width=650; "src=" Https://s1.51cto.com/wyfs02/M02/97/C2/wKioL1kyZySRN4uNAABIh0e2yCU615.png "title=" 98. PNG "alt=" Wkiol1kyzysrn4unaabih0e2ycu615.png "/>

650) this.width=650; "src=" Https://s2.51cto.com/wyfs02/M01/97/C4/wKiom1kypE-j8vUpAAArG_prDig793.png "title=" 108. PNG "alt=" Wkiom1kype-j8vupaaarg_prdig793.png "/>

B, write the method in the interface, pass in the parameter ID. and write the Resultmap and select tags in the SQL mapping file. (as you can see, property= "dept.id", description mybatis support cascading queries)

650) this.width=650; "src=" Https://s1.51cto.com/wyfs02/M01/97/C1/wKiom1kyaIPB6UX7AAAtRjugwUo150.png "title=" 99. PNG "alt=" Wkiom1kyaipb6ux7aaatrjugwuo150.png "/>

650) this.width=650; "src=" Https://s4.51cto.com/wyfs02/M01/97/C1/wKiom1kyaISApO3xAABSJq5enZI181.png "style=" float : none; "title=" 100.png "alt=" Wkiom1kyaisapo3xaabsjq5enzi181.png "/>

650) this.width=650; "src=" Https://s4.51cto.com/wyfs02/M01/97/C2/wKioL1kyaIXTFKpQAACPJskArwg905.png "title=" 101. PNG "alt=" Wkiol1kyaixtfkpqaacpjskarwg905.png "/>

C, the association label with the RESULTMAP label is defined (you need to specify the JavaBean type), you can also get the same effect.

650) this.width=650; "src=" Https://s2.51cto.com/wyfs02/M01/97/C1/wKiom1kybVyAvT-aAACl1iZcK4w964.png "title=" 102. PNG "alt=" Wkiom1kybvyavt-aaacl1izck4w964.png "/>

3, the Use of association for step-by query function:

A, preparation: Add a Departmentmapper interface (the interface defines the Getdeptbyid method) and a departmentmapper.xml mapping file. (The select tag is defined in the mapping file and mapped with the interface method)

650) this.width=650; "src=" Https://s1.51cto.com/wyfs02/M00/97/C3/wKioL1kydMKizBjNAAAmaHxvQZk848.png "title=" 103. PNG "alt=" Wkiol1kydmkizbjnaaamahxvqzk848.png "/>

650) this.width=650; "src=" Https://s1.51cto.com/wyfs02/M00/97/C3/wKioL1kydMKxdbTuAABHEWGWD6M001.png "title=" 104. PNG "alt=" Wkiol1kydmkxdbtuaabhewgwd6m001.png "/>

b, add the Getempbystep method to the Employeemapperplus interface, and add the Select tag in the Employeemapper.xml file. (There is a association sub-tag in the select tag, the attribute select is defined in the label, and column (the field that needs to be passed in))

650) this.width=650; "src=" Https://s1.51cto.com/wyfs02/M00/97/C2/wKiom1kyde2yL9IaAAA2RvAYOsY260.png "title=" 106. PNG "alt=" Wkiom1kyde2yl9iaaaa2rvayosy260.png "/>

650) this.width=650; "src=" Https://s3.51cto.com/wyfs02/M01/97/C2/wKiom1kydafRdOS6AABGChq72zE989.png "title=" 105. PNG "alt=" Wkiom1kydafrdos6aabgchq72ze989.png "/>

Note: The deferred load setting for a step-by-point query sets two properties in the global configuration file (that is, the Mybatis-config.xml file). (In Settings tags)

650) this.width=650; "src=" Https://s4.51cto.com/wyfs02/M02/97/C4/wKioL1kyfHTyc3XxAAAtFUoG0tA790.png "title=" 107. PNG "alt=" Wkiol1kyfhtyc3xxaaatfuog0ta790.png "/>

4. Collection defines the wrapper rules for association objects:

A, add the list property of the Employee to the Departmnet class, and add a Getdeptbyidplus method to the Departmentmapper interface.

650) this.width=650; "src=" Https://s4.51cto.com/wyfs02/M00/97/C6/wKioL1kypY_RJtETAAAPzLyD2bk121.png "title=" 109. PNG "alt=" Wkiol1kypy_rjtetaaapzlyd2bk121.png "/>

650) this.width=650; "src=" Https://s4.51cto.com/wyfs02/M01/97/C4/wKiom1kypY_DOkaFAAAv3dCDZqc741.png "title=" 110. PNG "alt=" Wkiom1kypy_dokafaaav3dcdzqc741.png "/>

b, as you can see, add a Select tag to the Departmentmapper.xml SQL mapping file, and SQL in the label uses a left outer join to correlate the tbl_employees and tbl_depts two tables. and use the collection tag in the RESULTMAP tag to encapsulate the collection properties. (OfType represents the element type in the collection)

650) this.width=650; "src=" Https://s5.51cto.com/wyfs02/M01/97/C6/wKioL1kypZCAvACJAAC1WJ_YgE0187.png "title=" 111. PNG "alt=" Wkiol1kypzcavacjaac1wj_yge0187.png "/>

C, shown, the test results are not a problem, showing the expected results

650) this.width=650; "src=" Https://s1.51cto.com/wyfs02/M01/97/C6/wKioL1kypZGQPD4fAAA6AAeQkuE953.png "title=" 112. PNG "alt=" Wkiol1kypzgqpd4faaa6aaeqkue953.png "/>

650) this.width=650; "src=" Https://s1.51cto.com/wyfs02/M02/97/C4/wKiom1kypZHy9DaUAABQ4rxJ-6M437.png "title=" 113. PNG "alt=" Wkiom1kypzhy9dauaabq4rxj-6m437.png "/>

5, the use of collection tags for the step query function:

A, add the Getempbydeptid method to the Employeemapperplus interface, and add a select tag in the Employeemapperplus.xml SQL mapping file to remove the qualifying record.

650) this.width=650; "src=" Https://s5.51cto.com/wyfs02/M02/97/C6/wKiom1kysP-haGnSAAA_0EPuqYU978.png "title=" 120. PNG "alt=" Wkiom1kysp-hagnsaaa_0epuqyu978.png "/>

650) this.width=650; "src=" Https://s5.51cto.com/wyfs02/M02/97/C7/wKioL1kysQDjlDx2AAAQjyK2MYk382.png "title=" 122. PNG "alt=" Wkiol1kysqdjldx2aaaqjyk2myk382.png "/>

b, add a Getdeptbyid interface in the Departmentmapper interface, add a collection tag to the Departmentmapper.xml SQL mapping file, add the Select attribute to the label, and the Employee Mapperplus.getempbydeptid is associated with the column= "id", which represents the passed-in parameter ID.

650) this.width=650; "src=" Https://s5.51cto.com/wyfs02/M02/97/C7/wKioL1kysL6igclcAAAw2RSShxw878.png "style=" float : none; "title=" 118.png "alt=" Wkiol1kysl6igclcaaaw2rsshxw878.png "/>

650) this.width=650; "src=" Https://s5.51cto.com/wyfs02/M00/97/C6/wKiom1kysL_DZpQEAAA8500k20A467.png "style=" float : none; "title=" 119.png "alt=" Wkiom1kysl_dzpqeaaa8500k20a467.png "/>

C, test output results, no problem.

650) this.width=650; "src=" Https://s5.51cto.com/wyfs02/M00/97/C8/wKioL1kysr6hsfdOAAC1WJ_YgE0972.png "title=" 111. PNG "alt=" Wkiol1kysr6hsfdoaac1wj_yge0972.png "/>

Note: Use column for multi-column value passing

Multi-column value passing can encapsulate map delivery---> column= "{key1=column1, key2=column2}, such as:

650) this.width=650; "src=" Https://s4.51cto.com/wyfs02/M02/97/C8/wKioL1kytRjC9UURAAAu08Z1Wig269.png "title=" 125. PNG "alt=" Wkiol1kytrjc9uuraaau08z1wig269.png "/>

This article is from the "12392717" blog, please be sure to keep this source http://12402717.blog.51cto.com/12392717/1931980

MyBatis SQL mapping File Select tag and application to Resultmap tag