如何对SAP数据库表进行增删改查操作(2)?

本篇接着上一篇博文，继续讲解如何在 SAP 系统外部，方便地对 SAP 的数据库表进行增删改查操作。推荐的方式：

• SAP 暴露 OData 服务供外部调用
• SAP 暴露 Restful Service 供外部调用

总的来说，OData 是比较新的 Restful Service 规范，在 SAP 端编写代码相对容易，但早期版本不支持 OData; Restful Service 基本上较早的版本也可以实现。关于 OData 对 Netweaver 版本要求，请参考我另外一篇博文：

SAPUI5 (34) - OData Model 连接后端 SAP 系统 (上)

对于异构系统的接口，我比较喜欢服务化这个表述，Restful Service 能够很好地体现服务化思想。站在第三方系统的角度，不管是 push 还是 pull 都能实现。

本文介绍基于 .net 平台的 WinForm 框架如何实现 SAP 表的维护界面。在前端技术日新月异的今天，WinForm 少有人用，但 WinForm 作为 Microsoft 早期的平台技术，技术成熟，使用简单，而且 Office 的 开发技术 VSTO ，允许使用 WinForm 框架，所以可以在 Office 中编写界面，这也是极为有用的一个应用场景。

RestSharp

我选择开源的 RestSharp 框架作为调用 Restful Service 的技术，RestSharp 使用起来灵活、强大。为了减少后续代码量，我对 HTTP 的 GET / POST / PUT / DELETE 请求进行封装，认证方式选择 Http Basic Authentication:

using RestSharp;
using RestSharp.Authenticators;
using System;

namespace RestSharpCRUD
{
    public class RestSharpHelper
    {
        private String username;
        private String password;

        public String BaseUrl { get; set; }

        private RestClient client;

        public RestSharpHelper(String baseUrl, String username, String password)
        {
            this.BaseUrl = baseUrl;
            this.username = username;
            this.password = password;

            // construct RestClient object
            client = new RestClient(this.BaseUrl)
            {
                Authenticator = new HttpBasicAuthenticator(username, password)
            };
        }

        public IRestResponse Get(String resource)
        {
            var req = new RestRequest(resource, Method.GET);
            var resp = client.Execute(req);

            return resp;
        }

        public IRestResponse Post(String resource, String payload)
        {
            var req = new RestRequest(resource, Method.POST);
            req.RequestFormat = DataFormat.Json;
            req.AddJsonBody(payload);
            req.AddParameter("application/json", payload, ParameterType.RequestBody);

            var resp = client.Execute(req);

            return resp;
        }

        public IRestResponse Put(String resource, String payload)
        {
            var req = new RestRequest(resource, Method.PUT);
            req.RequestFormat = DataFormat.Json;
            req.AddJsonBody(payload);
            req.AddParameter("application/json", payload, ParameterType.RequestBody);

            var resp = client.Execute(req);

            return resp;
        }

        public IRestResponse Delete(String resource)
        {
            var req = new RestRequest(resource, Method.DELETE);
            var resp = client.Execute(req);

            return resp;
        }
    }
}

Model 类

Model 类比较简单，代码如下：

using System;

namespace RestSharpCRUD {
    public class EmpEntity {
        public EmpEntity() {
            MANDT = "001";
        }

        public String MANDT { get; set; }
        public String EMPID { get; set; }
        public String EMPNAME { get; set; }
        public String EMPADDR { get; set; }
    }
}

调用 Restful Service

封装了 Http 方法后，接下来编写一个类，实现通过调用 Restful Service 来对 SAP zemployee 表增删改查操作：

using Newtonsoft.Json;
using System;
using System.Collections.Generic;

namespace RestSharpCRUD {
    public class EmpService {
        private String baseUrl = "http://sapecc6:8000";
        private String username = "stone";
        private String password = "123456";

        private RestSharpHelper restSharpHelper;

        public EmpService() {
            restSharpHelper = new RestSharpHelper(baseUrl, username, password);
        }

        public IList<EmpEntity> ListAll() {
            IList<EmpEntity> employees = null;

            var resp = restSharpHelper.Get("/zrest/employees");
            if (!resp.IsSuccessful) {                
                throw new Exception(resp.ErrorMessage);                
            }

            employees = JsonConvert.DeserializeObject<List<EmpEntity>>(resp.Content);
                       
            return employees;  
        }

        public bool Create(EmpEntity emp) {
            String payload = JsonConvert.SerializeObject(emp);

            // Call POST method
            var resp = restSharpHelper.Post("/zrest/employees/create", payload);

            if (!resp.IsSuccessful) {
                throw new Exception(resp.Content);
            }

            return true;
        }

        public bool Update(EmpEntity emp) {
            String payload = JsonConvert.SerializeObject(emp);

            // Call POST method
            var resource = String.Format("/zrest/employees/{0}", emp.EMPID);
            var resp = restSharpHelper.Put(resource, payload);

            if (!resp.IsSuccessful) {
                throw new Exception(resp.Content);
            }

            return true;
        }

        public bool Delete(String empId) {
            bool rv = false;

            var resource = String.Format("/zrest/employees/{0}", empId);
            var resp = restSharpHelper.Delete(resource);
            if (resp.IsSuccessful) rv = true;

            return rv;
        }        
    }
}

界面实现

我通过两个 Form 的配合来实现增删改查操作。第一个 Form 罗列所有的 employee，允许在 Form 中进行导航，双击跳转到维护的 Form，可以在这个 Form 中进行删除操作。设计时的界面如下：

代码如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows.Forms;

namespace RestSharpCRUD
{
    public partial class EmpListForm : Form
    {
        public EmpListForm()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // 加载数据
            IList<EmpEntity> employees = null;
            try {
                employees = LoadEmployees();
            }
            catch (Exception ex) {
                MessageBox.Show(ex.Message);
                return;
            }

            // 数据绑定到控件
            // List绑定到DataGridView不能进行增删改查，所以将List转换为BindingList
            // DataGridView.DataSource = new BindingList<T>(List<T>);  
            bindingSource1.DataSource = new BindingList<EmpEntity>(employees);
            dataGridView1.DataSource = bindingSource1;
            bindingNavigator1.BindingSource = bindingSource1;
        }

        private void DataGridView1_CellDoubleClick(object sender, DataGridViewCellEventArgs e)
        {
            // 双击打开EmpSingleForm
            var empSingleForm = new EmpSingleForm(bindingSource1);
            empSingleForm.ShowDialog();
        }

        private void BindingNavigatorAddNewItem_Click(object sender, EventArgs e)
        {
            this.bindingSource1.AddNew();
            var empSingleForm = new EmpSingleForm(bindingSource1, true);
            empSingleForm.ShowDialog();
        }

        private void BindingNavigatorDeleteItem_Click(object sender, EventArgs e)
        {
            DoDelete();
        }

        private IList<EmpEntity> LoadEmployees()
        {
            var empService = new EmpService();
            IList<EmpEntity> employees = empService.ListAll();
            return employees;
        }

        private void DoDelete()
        {
            if (bindingSource1.Current == null) return;

            if (MessageBox.Show("确定删除这个员工吗？", "删除",
                                MessageBoxButtons.YesNo,
                                MessageBoxIcon.Question) == DialogResult.Yes) {
                var empId = (bindingSource1.Current as EmpEntity).EMPID;

                var empService = new EmpService();
                bool rv = empService.Delete(empId);
                if (rv) {
                    bindingSource1.RemoveCurrent(); // 保持界面同步
                }
            }
        }
    }
}

UI 层与 Service 层交互，使用的是 IList<T> 格式，使用这种格式，在界面中要将 IList<T>，转换为 BindingList<T>，否则不支持 CRUD 操作。

在 EmpSingleForm 表单中，对单笔记录进行更新和保存，表单设计时界面如下：

两个表单都基于 BindingSource 控件对数据进行绑定，并且通过 BindingSource 控件在 Form 中交换数据，从而减少代码量，为此，在 EmpSingleForm 中，特意实现另外两个构造函数：

#region constructors

public EmpSingleForm()
{
    InitializeComponent();
}

public EmpSingleForm(BindingSource bs) : this()
{
    empBs = bs;

    //设置数据绑定
    SetBinding();
}

public EmpSingleForm(BindingSource bs, bool addNew) : this(bs)
{
    isAddNewMode = addNew;
}

#endregion 

SetBinding() 方法负责数据的绑定：

private void SetBinding()
{
    txtEmpID.DataBindings.Add("Text", empBs, "EMPID", true);
    txtName.DataBindings.Add("Text", empBs, "EMPNAME", true);
    txtAddress.DataBindings.Add("Text", empBs, "EMPADDR", true);
}

将更新的数据保存到 SAP 后端，无非就是调用 EmpService 类的方法：

private void BtnSave_Click(object sender, System.EventArgs e)
{
    bool rv = false; // return value

    var emp = new EmpEntity
    {
        MANDT = "001",
        EMPID = txtEmpID.Text.Trim(),
        EMPNAME = txtName.Text.Trim(),
        EMPADDR = txtAddress.Text.Trim()
    };

    var empService = new EmpService();
    
    if (isAddNewMode) {
        try {
            rv = empService.Create(emp);
        }
        catch (Exception ex) {
            MessageBox.Show(ex.Message);
        }
    }
    else {
        rv = empService.Update(emp);
    }

    if (rv) {
        empBs.EndEdit();
        this.Close();
    }
}

以下是 EmpSingleForm 的完整代码：

using System;
using System.Windows.Forms;

namespace RestSharpCRUD
{
    public partial class EmpSingleForm : Form
    {
        private bool isAddNewMode = false;

        #region constructors

        public EmpSingleForm()
        {
            InitializeComponent();
        }

        public EmpSingleForm(BindingSource bs) : this()
        {
            empBs = bs;

            //设置数据绑定
            SetBinding();
        }

        public EmpSingleForm(BindingSource bs, bool addNew) : this(bs)
        {
            isAddNewMode = addNew;
        }

        #endregion 

        private void EmpSingleForm_FormClosed(object sender, FormClosedEventArgs e)
        {
            this.empBs.CancelEdit();
        }

        private void BtnSave_Click(object sender, System.EventArgs e)
        {
            bool rv = false; // return value

            var emp = new EmpEntity
            {
                MANDT = "001",
                EMPID = txtEmpID.Text.Trim(),
                EMPNAME = txtName.Text.Trim(),
                EMPADDR = txtAddress.Text.Trim()
            };

            var empService = new EmpService();
            
            if (isAddNewMode) {
                try {
                    rv = empService.Create(emp);
                }
                catch (Exception ex) {
                    MessageBox.Show(ex.Message);
                }
            }
            else {
                rv = empService.Update(emp);
            }

            if (rv) {
                empBs.EndEdit();
                this.Close();
            }
        }

        private void EmpSingleForm_Load(object sender, EventArgs e)
        {
            txtEmpID.Enabled = (isAddNewMode == true);
        }

        private void SetBinding()
        {
            txtEmpID.DataBindings.Add("Text", empBs, "EMPID", true);
            txtName.DataBindings.Add("Text", empBs, "EMPNAME", true);
            txtAddress.DataBindings.Add("Text", empBs, "EMPADDR", true);
        }
    }
}

程序源码

该工程完整的代码在 github。